Mock Exam 09
Mock Exam 09: Reproductive Physiology & Endocrinology
100 MRCOG Part 1 SBA Practice Questions
📘 Q1 (Physiology) — During the early follicular phase of the menstrual cycle, which of the following hormonal changes is primarily responsible for the recruitment and selection of the dominant ovarian follicle? A) Rising inhibin B levels from the dominant follicle suppressing FSH B) A sustained rise in luteinising hormone (LH) pulse frequency C) A progressive decline in follicle-stimulating hormone (FSH) levels below a threshold D) A transient inter-cycle rise in FSH that exceeds the ovarian threshold E) Rising oestradiol from the corpus luteum of the preceding cycle
Answer: D
The inter-cycle FSH rise (late luteal to early follicular phase) occurs as oestradiol, progesterone, and inhibin A fall after corpus luteum regression, releasing the pituitary from negative feedback. This FSH surge exceeds the ovarian threshold needed for follicular recruitment. The dominant follicle is selected when its rising oestradiol and inhibin B progressively suppress FSH below the threshold required for less mature follicles.
📘 Q2 (Physiology) — Which of the following best describes the change in gonadotrophin-releasing hormone (GnRH) pulse frequency across the normal menstrual cycle? A) Low frequency in the follicular phase, high frequency in the luteal phase B) High frequency in the follicular phase, low frequency in the luteal phase C) Constant frequency throughout the cycle with varying amplitude D) High frequency only at the mid-cycle surge E) GnRH is secreted at high amplitude but constant frequency throughout
Answer: B
GnRH pulse frequency is rapid (approximately one pulse per 60–90 minutes) during the follicular phase, favouring FSH synthesis and secretion. In the luteal phase, progesterone and oestradiol slow GnRH pulse frequency to approximately one pulse every 2–4 hours, which favours LH synthesis. This frequency modulation is a key mechanism for differential gonadotrophin regulation.
📘 Q3 (Physiology) — Regarding ovarian steroidogenesis, which enzyme is deficient in the theca interna cells such that they cannot directly produce oestradiol? A) 17α-hydroxylase (CYP17A1) B) 3β-hydroxysteroid dehydrogenase (3β-HSD) C) Aromatase (CYP19A1) D) 17β-hydroxysteroid dehydrogenase (17β-HSD) E) 21β-hydroxylase (CYP21A2)
Answer: C
Theca interna cells express CYP17A1 and 3β-HSD, allowing them to convert cholesterol to androstenedione and testosterone under LH stimulation. However, they lack aromatase (CYP19A1), which is expressed in granulosa cells under FSH regulation. Androgens produced by theca cells diffuse across the basement membrane to granulosa cells, where aromatase converts them to oestrogens — the basis of the two-cell, two-gonadotrophin model.
📘 Q4 (Endocrinology) — A 32-year-old woman presents with secondary amenorrhoea and galactorrhoea. Her serum prolactin is 180 ng/mL (normal <25 ng/mL). Which of the following is the most likely cause? A) Polycystic ovary syndrome B) Craniopharyngioma C) Prolactin-secreting pituitary microadenoma D) Sheehan syndrome E) Empty sella syndrome
Answer: C
Hyperprolactinaemia with amenorrhoea and galactorrhoea is most commonly caused by a prolactinoma. Prolactin inhibits GnRH pulsatility via hypothalamic dopaminergic pathways, suppressing gonadotrophin secretion and causing anovulation. A prolactin level >100 ng/mL is highly suggestive of a prolactinoma, while levels <100 ng/mL may be due to drugs (e.g. antipsychotics), hypothyroidism, or stalk compression.
📘 Q5 (Physiology) — During the mid-luteal phase of the menstrual cycle, the endometrium is most receptive to embryo implantation. Which of the following markers best characterises this window of implantation? A) Maximal oestrogen receptor expression in the stroma B) Pinopode formation on the endometrial surface epithelium C) Maximal endometrial厚度 of 5–7 mm on ultrasound D) Peak expression of leukaemia inhibitory factor (LIF) in the glandular epithelium E) Decidualisation of the entire endometrium under the action of oestradiol alone
Answer: B
Pinopodes are bleb-like projections on the apical surface of the endometrial epithelium that appear during the window of implantation (cycle days 20–24) under the influence of progesterone. They are markers of endometrial receptivity and facilitate embryo attachment. While LIF is important for implantation, pinopode formation is the most characteristic morphological marker of the receptive phase.
📘 Q6 (Physiology) — Which of the following hormonal changes initiates the onset of parturition in humans? A) A sharp rise in fetal cortisol stimulating placental CRH production B) A fall in maternal progesterone oestradiol ratio at term C) A surge in maternal oxytocin from the posterior pituitary D) Activation of the fetal hypothalamic–pituitary–adrenal (HPA) axis with increased oestrogen synthesis E) Increased prostaglandin synthesis by the amnion alone
Answer: A
In humans, parturition is thought to be initiated by fetal cortisol secretion, which stimulates the placenta to produce corticotrophin-releasing hormone (CRH). Placental CRH acts as a placental clock, driving further fetal cortisol production and increasing oestrogen synthesis. This leads to upregulation of connexin-43 (gap junctions), oxytocin receptors, and prostaglandin synthesis, ultimately triggering labour.
📘 Q7 (Endocrinology) — In the two-cell, two-gonadotrophin model of oestradiol synthesis, which of the following correctly pairs each cell type with its primary gonadotrophin stimulus? A) Theca interna — FSH; Granulosa — LH B) Granulosa — LH; Theca interna — FSH C) Theca interna — LH; Granulosa — FSH D) Both cell types respond equally to LH and FSH E) Theca interna responds to prolactin; Granulosa responds to LH
Answer: C
In the two-cell, two-gonadotrophin model, LH stimulates theca interna cells to produce androgens (androstenedione and testosterone) from cholesterol. These androgens then diffuse to granulosa cells, where FSH stimulates aromatase to convert them to oestradiol. This compartmentalisation ensures coordinated follicular oestrogen production.
📘 Q8 (Physiology) — A pregnant woman at 36 weeks gestation has a fasting plasma glucose of 5.2 mmol/L. Which of the following best explains the physiological changes in carbohydrate metabolism during late pregnancy? A) Increased maternal insulin sensitivity due to rising oestradiol B) Decreased hepatic gluconeogenesis to conserve glucose for the fetus C) Progressive insulin resistance mediated by human placental lactogen (hPL) and tumour necrosis factor-alpha D) Reduced maternal pancreatic beta-cell function to limit fetal growth E) Increased maternal glucose clearance due to fetal glucose utilisation alone
Answer: C
Late pregnancy is characterised by progressive insulin resistance driven by placental hormones, particularly human placental lactogen (hPL), placental growth hormone, cortisol, and TNF-α. This ensures a continuous glucose supply to the fetus. The maternal pancreas compensates by increasing beta-cell mass and insulin secretion. When this compensation is insufficient, gestational diabetes mellitus develops.
📘 Q9 (Physiology) — Which of the following describes the normal change in maternal blood volume during a singleton pregnancy? A) No significant change throughout gestation B) An increase of approximately 10% by term C) An increase of approximately 40–50% by term D) A decrease of 20% due to haemodilution E) An increase of 80–100% by term
Answer: C
Maternal blood volume increases by approximately 40–50% (about 1.5 L) in a singleton pregnancy, with plasma volume increasing proportionally more than red cell mass, leading to physiological anaemia of pregnancy. This expansion begins in the first trimester, plateaus in the third trimester, and is mediated by aldosterone, oestrogen, and the renin–angiotensin–aldosterone system.
📘 Q10 (Physiology) — Which of the following best describes the change in cardiac output during normal pregnancy? A) Cardiac output remains unchanged but heart rate increases B) Cardiac output increases by 30–50% by the end of the second trimester C) Cardiac output decreases in the third trimester due to aortocaval compression D) Cardiac output increases only during labour E) Cardiac output increases by 10% in the first trimester and then plateaus
Answer: B
Cardiac output increases by 30–50% during pregnancy, primarily due to increased stroke volume in early pregnancy and increased heart rate later. The rise begins as early as 5 weeks' gestation and peaks by 24–32 weeks. Although aortocaval compression in the supine position can transiently reduce cardiac output near term, the overall increase is maintained until delivery.
📘 Q11 (Endocrinology) — A woman with hypothyroidism at 12 weeks gestation has a TSH of 8.5 mIU/L. Which of the following physiological changes explains why levothyroxine requirements increase in pregnancy? A) Decreased thyroxine-binding globulin (TBG) levels due to oestrogen B) Increased clearance of thyroxine by the placenta C) Increased plasma volume and TBG levels, reducing free T4 availability D) Suppression of maternal TSH by hCG E) Increased delodinase activity in the fetal compartment only
Answer: C
Oestrogen stimulates hepatic TBG production, doubling TBG levels by mid-pregnancy. This, combined with a 50% increase in plasma volume, reduces free T4 availability despite normal or increased total T4. The increased thyroxine pool also undergoes enhanced renal clearance. Consequently, women with pre-existing hypothyroidism often require a 30–50% increase in levothyroxine dose during pregnancy.
📘 Q12 (Physiology) — Which of the following is the primary function of human chorionic gonadotrophin (hCG) in early pregnancy? A) Stimulating fetal adrenal development B) Maintaining the corpus luteum and its progesterone secretion C) Initiating uterine contractions at term D) Suppressing maternal immune response to the conceptus E) Stimulating breast development for lactation
Answer: B
hCG, secreted by the syncytiotrophoblast, acts on LH/hCG receptors in the corpus luteum to sustain progesterone production during the first 8–10 weeks of pregnancy. This is critical because the corpus luteum is the main source of progesterone until the luteal–placental shift occurs around 8–10 weeks, after which the placenta takes over progesterone synthesis.
📘 Q13 (Endocrinology) — Which of the following hormones has a circadian rhythm that is suppressed by light exposure and peaks during the night? A) Prolactin B) Growth hormone C) Cortisol D) Melatonin E) Oxytocin
Answer: D
Melatonin is synthesised and secreted by the pineal gland in a circadian pattern, with low levels during daylight and peak secretion during the night. Light inhibits melatonin synthesis via the retinohypothalamic tract and suprachiasmatic nucleus. Melatonin is involved in regulating sleep–wake cycles and may influence reproductive function via GnRH modulation.
📘 Q14 (Physiology) — During the proliferative phase of the endometrial cycle, the endometrium thickens primarily under the influence of: A) Progesterone from the corpus luteum B) Oestradiol from the developing ovarian follicle C) Follicle-stimulating hormone from the anterior pituitary D) Human chorionic gonadotrophin from the conceptus E) Prolactin from the anterior pituitary
Answer: B
The proliferative phase (days 5–14 of a 28-day cycle) is driven by rising oestradiol from the developing ovarian follicle. Oestradiol stimulates proliferation of the endometrial glands, stroma, and blood vessels, doubling the endometrial thickness from approximately 2 mm to 10 mm. Mitotic activity is prominent in both glandular and stromal cells during this phase.
📘 Q15 (Physiology) — What is the primary mechanism by which progesterone prevents endometrial proliferation during the secretory phase? A) Increasing oestrogen receptor expression endometrial cells B) Inducing 17β-hydroxysteroid dehydrogenase and sulphotransferase activity in the endometrium C) Enhancing aromatase activity in endometrial stromal cells D) Directly inhibiting mitotic activity of endometrial cells E) Suppressing pituitary FSH secretion
Answer: B
Progesterone induces 17β-hydroxysteroid dehydrogenase (which converts oestradiol to the less potent oestrone) and sulphotransferase (which sulphates oestrogens, rendering them inactive) in endometrial cells. This functionally reduces local oestrogenic activity and prevents continued proliferation. Progesterone also induces secretory transformation of the endometrium, preparing it for implantation.
📘 Q16 (Physiology) — Which of the following describes the fertilisation process in humans? A) Sperm binds to the zona pellucida via the acrosome reaction, which occurs before binding B) The sperm acrosome reaction is triggered by progesterone released from the cumulus oophorus C) The cortical reaction prevents polyspermy by inactivating sperm receptors on the zona pellucida D) The first sperm to contact the oolemma triggers completion of meiosis I only E) Sperm entry occurs through the region overlying the metaphase spindle exclusively
Answer: C
After sperm penetration, cortical granules beneath the oolemma release enzymes (e.g. ovoperoxidase, proteases) that modify the zona pellucida, hardening it and inactivating sperm-binding receptors (ZP2, ZP3). This cortical reaction — also known as the zona reaction — is the primary slow block to polyspermy in humans. The fast block involves depolarisation of the oolemma.
📘 Q17 (Physiology) — The luteal phase of the menstrual cycle is relatively fixed at approximately 14 days. Which of the following best explains this consistent duration? A) The lifespan of the corpus luteum is determined by the duration of LH support from the pituitary B) Progesterone from the corpus luteum feeds back to suppress LH, and the corpus luteum has an intrinsic lifespan of ~14 days if not rescued by hCG C) The corpus luteum spontaneously involutes due to apoptosis triggered by falling FSH D) Oestradiol from the corpus luteum induces endometrial shedding after 14 days E) The dominant follicle releases a fixed amount of LH at ovulation
Answer: B
The corpus luteum has an intrinsically programmed lifespan of approximately 14 days in the absence of pregnancy. If pregnancy occurs, hCG from the trophoblast rescues the corpus luteum by acting on LH/hCG receptors. The fall in progesterone towards the end of the luteal phase removes negative feedback, allowing FSH to rise for the next cycle. The corpus luteum's intrinsic limit is due to reduced responsiveness to tonic LH.
📘 Q18 (Endocrinology) — Which of the following best describes the role of kisspeptin in the hypothalamic control of reproduction? A) Kisspeptin directly stimulates LH secretion from the anterior pituitary B) Kisspeptin neurons in the arcuate nucleus stimulate GnRH release via the GPR54 (KISS1R) receptor C) Kisspeptin suppresses GnRH pulsatility during the luteal phase D) Kisspeptin is synthesised in the posterior pituitary and transported to the hypothalamus E) Kisspeptin inhibits prolactin secretion via tuberoinfundibular dopamine neurons
Answer: B
Kisspeptin, encoded by the KISS1 gene, is a critical neuropeptide secreted by neurons in the arcuate and anteroventral periventricular (AVPV) nuclei of the hypothalamus. It acts via the GPR54 (KISS1R) receptor on GnRH neurons to stimulate GnRH release. Mutations in KISS1R cause hypogonadotrophic hypogonadism. Kisspeptin signalling is modulated by oestradiol and is essential for the preovulatory LH surge.
📘 Q19 (Physiology) — During lactation, what is the primary stimulus for the milk ejection reflex? A) Suckling stimulates the release of prolactin from the anterior pituitary B) Suckling stimulates the release of oxytocin from the posterior pituitary C) Prolactin directly causes contraction of myoepithelial cells in the breast D) Oxytocin stimulates milk synthesis in the alveoli E) Progesterone withdrawal at delivery initiates milk secretion
Answer: B
The milk ejection (let-down) reflex is a neuroendocrine reflex. Suckling stimulates sensory nerve endings in the nipple and areola, sending afferent signals to the hypothalamus that trigger oxytocin release from the posterior pituitary. Oxytocin acts on myoepithelial cells surrounding the alveoli, causing them to contract and eject milk into the ducts. Prolactin, in contrast, stimulates milk synthesis.
📘 Q20 (Endocrinology) — Which of the following hormones is synthesised primarily in the zona fasciculata of the adrenal cortex? A) Aldosterone B) Oestradiol C) Cortisol D) Dehydroepiandrosterone (DHEA) E) Adrenaline
Answer: C
The adrenal cortex is divided into three zones: zona glomerulosa (mineralocorticoids, primarily aldosterone), zona fasciculata (glucocorticoids, primarily cortisol), and zona reticularis (adrenal androgens, primarily DHEA and DHEA-S). Cortisol is synthesised under the control of ACTH via the HPA axis. Adrenaline is produced in the adrenal medulla, not the cortex.
📘 Q21 (Physiology) — Which of the following best describes the maternal renal physiological adaptation during pregnancy? A) Glomerular filtration rate (GFR) decreases by 20% to conserve fluid B) Renal plasma flow (RPF) increases by 50–80% with a corresponding rise in GFR C) The renal threshold for glucose increases, so glycosuria is abnormal D) Ureteric peristalsis increases to prevent stasis E) Renal size decreases due to compression by the gravid uterus
Answer: B
In pregnancy, renal plasma flow increases by 50–80% and GFR increases by approximately 50%, peaking in the mid-second trimester. This results in decreased serum creatinine, urea, and urate. The renal threshold for glucose decreases, so glycosuria is common in normal pregnancy. The ureters dilate due to progesterone and mechanical compression, increasing the risk of urinary stasis and infection.
📘 Q22 (Endocrinology) — A woman at 28 weeks gestation has a 50 g oral glucose challenge test result of 8.2 mmol/L. Which of the following placental hormones is most strongly implicated in the physiological insulin resistance of pregnancy? A) Oestriol B) Progesterone C) Human placental lactogen (hPL) D) Human chorionic gonadotrophin (hCG) E) Placental growth hormone variant
Answer: C
Human placental lactogen (hPL), also known as human chorionic somatomammotropin (hCS), is structurally similar to growth hormone and is secreted by the syncytiotrophoblast. It is a major driver of maternal insulin resistance by inducing peripheral lipolysis and decreasing glucose utilisation in maternal tissues, thereby ensuring glucose availability for the fetus. Its levels rise progressively with placental mass.
📘 Q23 (Physiology) — In ovarian steroidogenesis, androstenedione is converted to oestrone by which enzyme? A) 17α-hydroxylase B) Aromatase (CYP19A1) C) 17β-hydroxysteroid dehydrogenase D) 5α-reductase E) 21-hydroxylase
Answer: B
Aromatase (CYP19A1) converts androgens to oestrogens: androstenedione to oestrone, and testosterone to oestradiol. This enzyme is expressed in granulosa cells of the ovary, as well as in adipose tissue, placenta, bone, and brain. In the ovary, aromatase activity is stimulated by FSH and is essential for oestrogen production from theca-derived androgens.
📘 Q24 (Physiology) — Which of the following describes the correct sequence of events in blastocyst implantation? A) Apposition → Adhesion → Invasion B) Adhesion → Apposition → Invasion C) Invasion → Apposition → Adhesion D) Apposition → Invasion → Adhesion E) Adhesion → Invasion → Apposition
Answer: A
Implantation proceeds in three sequential stages: (1) Apposition — the blastocyst orientates and loosely contacts the endometrial epithelium; (2) Adhesion — stronger attachment occurs via trophoblast cell adhesion molecules (integrins, cadherins); (3) Invasion — the trophoblast penetrates the endometrial epithelium and invades the stroma, establishing the early placenta. This process occurs around days 6–9 after fertilisation.
📘 Q25 (Endocrinology) — Which of the following correctly describes the action of prolactin on the hypothalamus to regulate its own secretion? A) Prolactin stimulates dopamine release from tuberoinfundibular neurons B) Prolactin inhibits dopamine release from tuberoinfundibular neurons C) Prolactin stimulates GnRH release D) Prolactin directly inhibits its own synthesis at the pituitary level E) Prolactin stimulates thyrotrophin-releasing hormone (TRH) secretion
Answer: A
Prolactin regulates its own secretion via a short-loop negative feedback mechanism. Prolactin acts on dopamine (DA) neurons in the arcuate nucleus (tuberoinfundibular pathway), stimulating DA release into the hypothalamic–pituitary portal circulation. Dopamine then binds to D2 receptors on pituitary lactotrophs, tonically inhibiting prolactin secretion. This explains why dopamine antagonists (e.g. antipsychotics) cause hyperprolactinaemia.
📘 Q26 (Physiology) — Which of the following hormonal changes occurs in response to maternal suckling during breastfeeding? A) A rise in dopamine and a fall in prolactin B) A rise in prolactin and a rise in oxytocin C) A rise in gonadotrophins and a fall in oxytocin D) A fall in prolactin and a rise in oxytocin E) A rise in FSH and a fall in prolactin
Answer: B
Suckling triggers two distinct neuroendocrine reflexes: (1) Prolactin release from the anterior pituitary, stimulated by suckling-induced inhibition of tuberoinfundibular dopamine neurons (disinhibition); and (2) Oxytocin release from the posterior pituitary. Prolactin promotes milk synthesis, while oxytocin causes milk ejection. The rise in prolactin also suppresses GnRH, contributing to lactational amenorrhoea.
📘 Q27 (Physiology) — Which of the following best describes the changes in maternal respiratory physiology during pregnancy? A) Tidal volume decreases, respiratory rate increases significantly B) Functional residual capacity (FRC) increases due to diaphragmatic splinting C) Minute ventilation increases by 40%, primarily due to increased tidal volume D) Residual volume increases due to the growing uterus E) Arterial pCO₂ rises to 40–45 mmHg to facilitate CO₂ transfer to the fetus
Answer: C
Minute ventilation increases by approximately 40% during pregnancy, driven mainly by an increase in tidal volume (not respiratory rate). This is mediated by progesterone, which increases the sensitivity of the respiratory centre to CO₂. The resulting chronic mild hyperventilation lowers arterial pCO₂ to about 28–32 mmHg, facilitating CO₂ diffusion from the fetus across the placenta. Functional residual capacity decreases due to diaphragmatic elevation.
📘 Q28 (Endocrinology) — In the context of calcium metabolism in pregnancy, which of the following statements is correct? A) Total serum calcium decreases but ionised calcium remains unchanged B) Parathyroid hormone (PTH) levels fall to conserve maternal bone C) 1,25-dihydroxyvitamin D levels decrease due to placental conversion D) Calcitonin levels fall to promote maternal bone resorption E) Calcium absorption from the gut decreases to meet fetal demands
Answer: A
During pregnancy, total serum calcium falls due to haemodilution and reduced albumin, but ionised (free) calcium remains normal. Oestrogen and placental lactogen stimulate 1α-hydroxylase, increasing 1,25-dihydroxyvitamin D levels, which enhances intestinal calcium absorption. PTH levels are slightly suppressed or normal. The fetus actively transports calcium across the placenta, accumulating approximately 30 g by term.
📘 Q29 (Physiology) — Which of the following is the predominant oestrogen produced by the placenta during pregnancy? A) Oestrone (E1) B) Oestradiol (E2) C) Oestriol (E3) D) Oestetrol (E4) E) Equilin
Answer: C
Oestriol (E3) is the predominant oestrogen in pregnancy, accounting for 90% of urinary oestrogens. The placenta synthesises oestriol from fetal adrenal DHEA-S via 16α-hydroxylation in the fetal liver. Because oestriol synthesis depends on fetal precursors, maternal serum oestriol levels have historically been used as a marker of fetal well-being. Oestriol is a weaker oestrogen than oestradiol.
📘 Q30 (Physiology) — During the menstrual cycle, the LH surge triggers the resumption of meiosis in the oocyte. At which stage of meiosis is the oocyte arrested immediately before the LH surge? A) Prophase of meiosis I (germinal vesicle stage) B) Metaphase of meiosis I C) Telophase of meiosis I D) Metaphase of meiosis II E) Anaphase of meiosis II
Answer: A
The oocyte is arrested in prophase of meiosis I (the germinal vesicle stage, with an intact nuclear envelope) from fetal life until the LH surge. The LH surge triggers meiotic resumption, leading to completion of meiosis I and extrusion of the first polar body. The oocyte then progresses to metaphase II, where it arrests again until fertilisation.
📘 Q31 (Endocrinology) — Which of the following receptors mediates the inhibitory effect of dopamine on prolactin secretion? A) D1 receptor B) D2 receptor C) D3 receptor D) D4 receptor E) D5 receptor
Answer: B
Dopamine inhibits prolactin secretion by binding to D2 receptors on anterior pituitary lactotrophs. These are Gi-coupled receptors that decrease intracellular cyclic AMP, reducing prolactin gene transcription and secretion. D2 receptor antagonists (e.g. metoclopramide, domperidone, antipsychotics) therefore cause hyperprolactinaemia by blocking this tonic inhibition.
📘 Q32 (Physiology) — In the non-pregnant state, which of the following pituitary gonadotrophins is primarily responsible for stimulating follicular growth and development? A) Luteinising hormone (LH) B) Follicle-stimulating hormone (FSH) C) Prolactin D) Growth hormone E) Adrenocorticotrophic hormone (ACTH)
Answer: B
FSH is the primary hormone responsible for follicular recruitment and growth. It acts on granulosa cells to stimulate proliferation, aromatase activity, and inhibin B production. FSH receptors are expressed exclusively on granulosa cells. While LH acts on theca cells to provide androgen substrate, the initiation of follicular growth is FSH-dependent.
📘 Q33 (Physiology) — Which of the following correctly describes the luteal–placental shift? A) The corpus luteum takes over progesterone production from the placenta at 12 weeks B) The placenta becomes the dominant source of progesterone after 8–10 weeks' gestation C) hCG production shifts from the placenta to the corpus luteum D) Oestrogen production shifts from the placenta to the fetal adrenal gland E) Progesterone production shifts from the placenta to the fetal adrenal gland
Answer: B
The luteal–placental shift refers to the transition between approximately 8 and 10 weeks' gestation, when the placenta takes over from the corpus luteum as the primary source of progesterone. Before this shift, corpus luteum removal would cause pregnancy loss. After 10 weeks, the placenta produces sufficient progesterone (approximately 250 mg/day at term) to maintain the pregnancy independently.
📘 Q34 (Endocrinology) — Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency results in which of the following hormonal profiles? A) Decreased cortisol, decreased aldosterone, increased androgens B) Increased cortisol, increased aldosterone, decreased androgens C) Decreased cortisol, increased aldosterone, decreased androgens D) Increased cortisol, decreased aldosterone, increased androgens E) Decreased cortisol, decreased aldosterone, decreased androgens
Answer: A
21-Hydroxylase deficiency impairs conversion of 17-hydroxyprogesterone to 11-deoxycortisol (cortisol precursor) and progesterone to deoxycorticosterone (aldosterone precursor). This leads to cortisol deficiency and, in salt-wasting forms, aldosterone deficiency. The precursor accumulation shunts steroidogenesis towards androgen synthesis, causing hyperandrogenism. This results in virilisation of female genitalia in utero.
📘 Q35 (Physiology) — A woman has a mid-luteal phase progesterone level of 6 nmol/L. Which of the following is the most likely interpretation? A) She is in the periovulatory period B) She has ovulated and has normal luteal function C) She has ovulated but may have deficient luteal function D) She is pregnant E) She is in the early follicular phase
Answer: C
A mid-luteal progesterone level >25–30 nmol/L is generally considered evidence of ovulation and adequate luteal function. A level of 6 nmol/L suggests either anovulation or deficient luteal phase progesterone production, which may be associated with luteal phase deficiency and impaired endometrial receptivity. Progesterone levels peak approximately 7 days after ovulation.
📘 Q36 (Physiology) — Which of the following best describes the role of the syncytiotrophoblast layer of the placenta? A) It is a single layer of cells that proliferates to form anchoring villi B) It is the outermost multinucleated layer in direct contact with maternal blood, responsible for hormone synthesis and gas exchange C) It secretes hCG but does not participate in nutrient transport D) It differentiates from the inner cell mass of the blastocyst E) It forms the fetal blood vessels within the chorionic villi
Answer: B
The syncytiotrophoblast is a multinucleated, continuous layer that forms the outer surface of chorionic villi, directly bathed by maternal blood in the intervillous space. It is responsible for hormone secretion (hCG, hPL, progesterone, oestrogens), nutrient and gas exchange, and forms the maternal–fetal interface. It is derived from fusion of cytotrophoblast cells.
📘 Q37 (Endocrinology) — Which of the following is the earliest placental hormone detectable in maternal blood after implantation? A) Human placental lactogen (hPL) B) Progesterone C) Oestriol D) Human chorionic gonadotrophin (hCG) E) Placental growth hormone
Answer: D
hCG is secreted by the syncytiotrophoblast as early as 6–8 days after fertilisation, around the time of implantation. It is the basis for pregnancy testing. hCG can be detected in maternal blood by highly sensitive assays approximately 8–10 days after conception and in urine shortly thereafter. Its levels double approximately every 48 hours in early normal pregnancy.
📘 Q38 (Physiology) — Which of the following is the most important action of progesterone in maintaining pregnancy? A) Stimulating uterine contractions B) Promoting cervical ripening C) Maintaining uterine quiescence by reducing myometrial contractility D) Increasing oxytocin receptor expression E) Stimulating prostaglandin synthesis in the decidua
Answer: C
Progesterone maintains uterine quiescence throughout pregnancy by several mechanisms: it hyperpolarises myometrial cell membranes, reduces gap junction formation (connexin-43), decreases oxytocin receptor expression, and suppresses prostaglandin synthesis. At term, functional progesterone withdrawal (via changes in receptor isoform ratio) is a key event that allows the uterus to become contractile for labour.
📘 Q39 (Physiology) — Which of the following correctly describes the feedback effects of oestradiol on LH secretion during the menstrual cycle? A) Oestradiol exerts negative feedback only throughout the cycle B) Oestradiol exerts positive feedback only when levels are low C) Oestradiol has a biphasic effect: negative feedback at low levels and positive feedback at high sustained levels D) Oestradiol has no direct effect on LH secretion; it acts via inhibin E) Oestradiol exerts negative feedback on LH but positive feedback on FSH
Answer: C
Oestradiol has a classic biphasic feedback effect on LH secretion. During the follicular phase, low to moderate oestradiol levels suppress LH secretion (negative feedback). When oestradiol reaches a threshold level (approximately 200–300 pg/mL for 36–48 hours), it switches to positive feedback, triggering the mid-cycle LH surge. This surge is essential for ovulation.
📘 Q40 (Endocrinology) — Which of the following best describes the relationship between the HPA axis and the reproductive axis during chronic stress? A) Cortisol stimulates GnRH secretion to enhance reproductive function B) CRH suppresses GnRH secretion, contributing to stress-induced amenorrhoea C) ACTH directly stimulates ovarian oestrogen production D) Cortisol enhances LH pulsatility E) CRH stimulates kisspeptin release in the arcuate nucleus
Answer: B
Chronic stress activates the HPA axis, increasing CRH production. CRH suppresses hypothalamic GnRH pulsatility via direct and indirect mechanisms (including via β-endorphin and inhibition of kisspeptin neurons). This leads to reduced LH pulse frequency and amplitude, causing anovulation and amenorrhoea — a phenomenon known as functional hypothalamic amenorrhoea.
📘 Q41 (Physiology) — In the fetal adrenal gland, which zone involutes after birth? A) Zona glomerulosa B) Zona fasciculata C) Zona reticularis D) Fetal zone (fetal adrenal cortex) E) Adrenal medulla
Answer: D
The fetal adrenal has a distinct inner "fetal zone" that comprises 80–90% of the gland and produces large amounts of DHEA-S, which serves as a precursor for placental oestrogen synthesis. After birth, this fetal zone rapidly involutes via apoptosis over the first few weeks to months. The adult zones (glomerulosa, fasciculata, reticularis) develop from the outer definitive zone.
📘 Q42 (Physiology) — A term newborn is exclusively breastfed. Which of the following hormones is primarily responsible for the synthesis of milk in the mammary alveoli? A) Oxytocin B) Prolactin C) Oestradiol D) Progesterone E) Human placental lactogen
Answer: B
Prolactin is the primary hormone driving lactogenesis (milk synthesis). It acts on prolactin receptors in mammary alveolar epithelial cells to stimulate transcription of milk protein genes (e.g., casein, α-lactalbumin) and lipid synthesis. Prolactin secretion is triggered by suckling and is tonically inhibited by dopamine. Oxytocin, in contrast, is responsible for milk ejection, not synthesis.
📘 Q43 (Endocrinology) — Which of the following statements regarding the pineal gland and melatonin is correct? A) Melatonin is synthesised from tryptophan via serotonin B) Melatonin secretion peaks during daylight hours C) The pineal gland is directly innervated by the optic nerve D) Melatonin consistently suppresses GnRH in all mammals E) Melatonin is stored in large quantities in pinealocytes
Answer: A
Melatonin (N-acetyl-5-methoxytryptamine) is synthesised from tryptophan, which is converted to serotonin and then to melatonin via N-acetyltransferase and hydroxyindole-O-methyltransferase. Melatonin secretion is high at night and low during the day. In seasonal breeders, melatonin mediates reproductive responses to photoperiod, but its role in human reproduction is less pronounced. The pineal receives indirect photic input via the suprachiasmatic nucleus.
📘 Q44 (Physiology) — In the luteinised granulosa cells of the corpus luteum, which of the following enzymes is most critical for progesterone synthesis? A) Aromatase (CYP19A1) B) 17α-hydroxylase (CYP17A1) C) 3β-hydroxysteroid dehydrogenase (3β-HSD) D) 21-hydroxylase (CYP21A2) E) 11β-hydroxylase (CYP11B1)
Answer: C
After luteinisation, granulosa cells switch from oestrogen to progesterone production. 3β-HSD is the key enzyme that converts pregnenolone to progesterone in the corpus luteum. Luteinised granulosa cells (now called granulosa lutein cells) express 3β-HSD at high levels but downregulate aromatase and 17α-hydroxylase. LH/hCG maintains corpus luteum function via the cAMP/PKA pathway.
📘 Q45 (Physiology) — Which of the following best describes the maternal cardiovascular adaptation of increased stroke volume in early pregnancy? A) It is primarily due to increased venous return from the gravid uterus B) It is driven by increased heart rate alone C) It results from decreased systemic vascular resistance and increased preload D) It is mediated by increased maternal blood viscosity E) It is caused by compression of the aorta by the uterus
Answer: C
In early pregnancy (as early as 5 weeks), systemic vascular resistance decreases due to oestrogen-mediated vasodilation and the low-resistance uteroplacental circulation. This reduces afterload, while increased blood volume and renal sodium retention increase preload. The combination of increased preload and decreased afterload enhances stroke volume. Heart rate also increases, but the initial rise in cardiac output is primarily stroke volume-driven.
📘 Q46 (Endocrinology) — A woman with Sheehan syndrome (postpartum pituitary necrosis) would be expected to have which of the following hormonal findings? A) Elevated prolactin and low cortisol B) Low prolactin and low cortisol C) Elevated TSH and elevated ACTH D) Elevated LH and FSH E) Elevated growth hormone and low prolactin
Answer: B
Sheehan syndrome results from ischaemic necrosis of the anterior pituitary following postpartum haemorrhage. It leads to panhypopituitarism, including low prolactin (inability to lactate), low ACTH (secondary adrenal insufficiency), low TSH (secondary hypothyroidism), and low gonadotrophins. The classic presentation is failure to lactate with persistent postpartum amenorrhoea. Unlike prolactinomas, prolactin is low.
📘 Q47 (Physiology) — Which of the following maternal haematological changes is a normal physiological adaptation to pregnancy? A) Haemoglobin concentration rises to >13 g/dL B) White blood cell count falls to <4 × 10⁹/L C) Platelet count usually increases significantly D) Plasma volume increases by 40–50% while red cell mass increases by only 20–30% E) Clotting factor levels remain unchanged
Answer: D
In pregnancy, plasma volume increases disproportionately (40–50%) compared to red cell mass (20–30%), resulting in physiological haemodilution and a fall in haemoglobin concentration (the "physiological anaemia of pregnancy"). A mild leukocytosis is normal (up to 15 × 10⁹/L). Pregnancy is also a hypercoagulable state, with increased levels of factors VII, VIII, X, and fibrinogen, and decreased protein S.
📘 Q48 (Physiology) — During which stage of the menstrual cycle is the cervical mucus most receptive to sperm penetration? A) Menses B) Early follicular phase C) Around the time of ovulation D) Mid-luteal phase E) Late luteal phase
Answer: C
Around ovulation, high oestradiol levels stimulate cervical glands to produce abundant, clear, thin, elastic mucus with high spinnbarkeit (stretchability). This mucus has a fern-like pattern on air-drying and creates channels that facilitate sperm transport through the cervical canal. After ovulation, progesterone transforms the mucus into thick, scanty, cellular mucus that impedes sperm penetration.
📘 Q49 (Endocrinology) — Which of the following hormones is secreted by the posterior pituitary? A) Prolactin B) Growth hormone C) Adrenocorticotrophic hormone (ACTH) D) Oxytocin E) Thyroid-stimulating hormone (TSH)
Answer: D
The posterior pituitary (neurohypophysis) does not synthesise hormones but stores and releases oxytocin and vasopressin (antidiuretic hormone, ADH), which are produced in the supraoptic and paraventricular nuclei of the hypothalamus. Oxytocin is transported via axons to the posterior pituitary for release in response to suckling and cervical distension. All other options are anterior pituitary hormones.
📘 Q50 (Physiology) — In a normal 28-day menstrual cycle, ovulation typically occurs on which day relative to the LH surge? A) 12 hours before the LH surge B) At the peak of the LH surge C) Approximately 36–40 hours after the onset of the LH surge D) 5 days after the LH surge E) 7 days after the LH surge
Answer: C
Ovulation occurs approximately 36–40 hours after the onset of the LH surge (or about 10–12 hours after the LH peak). The LH surge triggers resumption of oocyte meiosis, luteinisation of granulosa cells, and production of proteolytic enzymes that weaken the follicle wall. The oocyte is released surrounded by the cumulus oophorus. This timing is important for fertility treatment and cycle monitoring.
📘 Q51 (Physiology) — Which of the following is the correct sequence of follicular development in the ovary? A) Primordial → Preantral → Antral → Graafian → Corpus luteum B) Preantral → Primordial → Graafian → Antral → Corpus luteum C) Primordial → Antral → Preantral → Graafian → Corpus luteum D) Graafian → Primordial → Preantral → Antral → Corpus luteum E) Primordial → Preantral → Graafian → Antral → Corpus luteum
Answer: A
Folliculogenesis proceeds from primordial follicles (the resting pool), which are recruited to become preantral (primary/secondary) follicles with a granulosa cell layer. Antral follicles develop a fluid-filled cavity, and one becomes the dominant Graafian follicle. After ovulation, the collapsed follicle becomes the corpus luteum. This process takes approximately 120 days from primordial to preovulatory stage.
📘 Q52 (Endocrinology) — A 28-year-old woman has elevated 17-hydroxyprogesterone levels on an early-morning blood test. Which of the following conditions is most likely? A) Cushing syndrome B) 21-Hydroxylase deficiency (non-classical CAH) C) Primary aldosteronism D) Prolactinoma E) Polycystic ovary syndrome
Answer: B
Non-classical (late-onset) 21-hydroxylase deficiency presents with hyperandrogenism, hirsutism, oligomenorrhoea, and elevated 17-hydroxyprogesterone (the substrate that accumulates due to enzyme block). Measurement of 17-hydroxyprogesterone, especially after ACTH stimulation, is diagnostic. This condition is one of the most common autosomal recessive disorders and can be mistaken for PCOS.
📘 Q53 (Physiology) — Which of the following is the primary factor determining the length of the menstrual cycle? A) The duration of the luteal phase, which varies between women B) The duration of the follicular phase, which varies between women C) The duration of menstruation, which varies between women D) The timing of the LH surge, which is fixed E) The lifespan of the corpus luteum, which varies if conception occurs
Answer: B
The length of the menstrual cycle is primarily determined by the duration of the follicular phase, which is variable (typically 10–16 days but can be longer). The luteal phase is relatively fixed at approximately 14 days (±2 days) due to the intrinsic lifespan of the corpus luteum. Therefore, cycle length variability between women and between cycles is mainly due to follicular phase length.
📘 Q54 (Endocrinology) — Which of the following hormones is synthesised in the magnocellular neurons of the hypothalamus and released from the posterior pituitary? A) Corticotrophin-releasing hormone (CRH) B) Gonadotrophin-releasing hormone (GnRH) C) Antidiuretic hormone (ADH, vasopressin) D) Somatostatin E) Thyrotrophin-releasing hormone (TRH)
Answer: C
ADH (vasopressin) and oxytocin are synthesised in the magnocellular neurons of the paraventricular and supraoptic nuclei of the hypothalamus. They are transported down axons to the posterior pituitary, where they are stored and released. All other listed hormones (CRH, GnRH, somatostatin, TRH) are synthesised in parvocellular neurons and released into the hypothalamic–pituitary portal system to regulate the anterior pituitary.
📘 Q55 (Physiology) — In early pregnancy, which of the following patterns of hCG change is most consistent with a normal intrauterine pregnancy? A) hCG levels remain static for the first 6 weeks B) hCG rises exponentially, doubling every 48 hours C) hCG rises linearly, increasing by 100 IU/L daily D) hCG reaches a peak at 4 weeks and then falls E) hCG levels are inversely related to progesterone levels
Answer: B
In a normal early pregnancy, hCG rises exponentially with a doubling time of approximately 48 hours until around 8–10 weeks. A slower rise (doubling time >72 hours) is suspicious for ectopic pregnancy or early pregnancy failure. hCG peaks at approximately 8–10 weeks (50,000–100,000 IU/L), then declines and plateaus at a lower level for the remainder of the pregnancy.
📘 Q56 (Endocrinology) — Which of the following is the most likely cause of galactorrhoea in a patient with primary hypothyroidism? A) Increased TRH stimulates both TSH and prolactin secretion B) Decreased dopamine synthesis in hypothyroidism C) Increased sensitivity of lactotrophs to oestrogen D) Direct stimulation of prolactin by low T4 E) Pituitary microprolactinoma secondary to hypothyroidism
Answer: A
TRH stimulates the release of both TSH and prolactin from anterior pituitary lactotrophs and thyrotrophs. In primary hypothyroidism, the lack of thyroid hormone feedback leads to elevated TRH secretion, which can cause hyperprolactinaemia and galactorrhoea. This resolves with thyroid hormone replacement therapy. This is an important diagnostic consideration in hyperprolactinaemic patients.
📘 Q57 (Physiology) — Which of the following changes occurs in the maternal coagulation system during pregnancy? A) Fibrinogen levels decrease to prevent thrombosis B) Protein S levels increase to promote anticoagulation C) Fibrinogen and factors VII, VIII, and X increase, creating a hypercoagulable state D) Platelet count increases significantly E) Prothrombin time (PT) and activated partial thromboplastin time (APTT) shorten mildly
Answer: C
Pregnancy is a hypercoagulable state, characterised by increased levels of fibrinogen (by 50%), factors VII, VIII, IX, X, and von Willebrand factor. Protein S (a natural anticoagulant) decreases, while protein C remains unchanged. These changes protect against haemorrhage at delivery but increase the risk of thromboembolism, which remains a leading cause of maternal mortality.
📘 Q58 (Physiology) — Which of the following best describes the role of the acrosome reaction in human fertilisation? A) It enables the sperm to penetrate the cumulus oophorus and bind to the zona pellucida B) It releases hydrolytic enzymes that digest the zona pellucida, allowing sperm penetration C) It triggers the completion of oocyte meiosis D) It prevents polyspermy by depolarising the oolemma E) It allows the sperm tail to fuse with the oolemma
Answer: B
The acrosome reaction involves exocytosis of the acrosomal cap contents, including hydrolytic enzymes such as acrosin and hyaluronidase, which digest a path through the zona pellucida. This reaction occurs after the sperm binds to the zona pellucida via ZP3 glycoproteins. The acrosome-reacted sperm then penetrates the zona and fuses with the oolemma. The reaction is calcium-dependent.
📘 Q59 (Physiology) — Which of the following is the most important contributor to the negative feedback suppression of FSH during the mid-luteal phase? A) Oestradiol alone B) Progesterone alone C) Inhibin A D) Inhibin B E) Activin
Answer: C
Inhibin A is secreted by the corpus luteum during the luteal phase and, together with oestradiol and progesterone, provides negative feedback to suppress pituitary FSH secretion. Inhibin B, in contrast, is secreted by granulosa cells of developing follicles during the follicular phase. The fall in inhibin A and oestradiol in the late luteal phase allows the inter-cycle FSH rise to begin.
📘 Q60 (Endocrinology) — Which of the following correctly describes the hypothalamic–pituitary–thyroid axis changes in pregnancy? A) hCG has weak thyrotrophic activity and can suppress TSH in the first trimester B) TSH levels rise throughout pregnancy due to oestrogen stimulation C) Free T4 levels double by the third trimester D) Thyroid-binding globulin levels decrease due to oestrogen E) The thyroid gland does not change in size during pregnancy
Answer: A
hCG has structural homology with TSH and can bind to TSH receptors, exhibiting weak thyrotrophic activity. High first-trimester hCG levels can transiently suppress TSH (gestational transient thyrotoxicosis). TBG levels double due to oestrogen, and the thyroid gland may increase slightly in size due to increased vascularity and mildly elevated TSH in some women. Free T4 levels remain within the normal range.
📘 Q61 (Physiology) — Which of the following best describes the mechanism of the preovulatory LH surge? A) Progesterone from the dominant follicle triggers the surge B) High sustained oestradiol levels for 36–48 hours exert positive feedback on the hypothalamus and pituitary C) Inhibin B from the dominant follicle triggers the surge D) Falling FSH levels trigger the surge via a rebound effect E) GnRH pulse frequency slows, stimulating LH over FSH
Answer: B
The preovulatory LH surge is triggered by sustained high oestradiol levels (approximately 200–300 pg/mL) from the dominant follicle for 36–48 hours. Oestradiol acts at both the hypothalamus (increasing GnRH pulse frequency and amplitude) and the anterior pituitary (increasing pituitary responsiveness to GnRH by upregulating GnRH receptors). This positive feedback mechanism is essential for ovulation.
📘 Q62 (Endocrinology) — A pregnant woman at 34 weeks has a fasting glucose of 5.5 mmol/L. A 75 g OGTT shows 2-hour glucose of 9.0 mmol/L. Which of the following best describes the pathophysiology of gestational diabetes mellitus (GDM)? A) Autoimmune destruction of pancreatic beta cells B) Insufficient insulin secretion relative to the degree of pregnancy-induced insulin resistance C) Increased hepatic glucose uptake causing hypoglycaemia D) Excessive glucagon secretion from the placenta E) Increased expression of GLUT4 in skeletal muscle
Answer: B
GDM develops when the maternal pancreas cannot secrete sufficient insulin to overcome the physiological insulin resistance of pregnancy. This insulin resistance is driven by placental hormones (hPL, placental GH, cortisol, TNF-α). Women with GDM have beta-cell dysfunction that becomes unmasked by the metabolic stress of pregnancy. Most return to normal glucose tolerance postpartum, though they have an increased risk of type 2 diabetes later in life.
📘 Q63 (Physiology) — Which of the following describes the normal changes in maternal respiratory gases during pregnancy? A) PaO₂ remains unchanged, PaCO₂ increases B) PaO₂ increases to 100 mmHg, PaCO₂ decreases to 28–32 mmHg C) PaO₂ decreases to 80 mmHg, PaCO₂ increases to 45 mmHg D) PaO₂ and PaCO₂ both remain unchanged E) PaO₂ decreases due to increased oxygen consumption, PaCO₂ increases
Answer: B
Due to progesterone-mediated hyperventilation, maternal PaO₂ rises to approximately 100–105 mmHg and PaCO₂ falls to around 28–32 mmHg (respiratory alkalosis). The kidneys compensate by increasing renal bicarbonate excretion, maintaining pH near normal. This gradient facilitates CO₂ transfer from the fetus to the mother and O₂ transfer to the fetus. The oxygen dissociation curve shifts rightward due to increased 2,3-BPG.
📘 Q64 (Physiology) — Which of the following events occurs during the process of capacitation? A) The sperm becomes motile for the first time B) The sperm undergoes the acrosome reaction C) Changes in the sperm plasma membrane allow it to undergo the acrosome reaction and achieve hyperactivated motility D) The sperm fuses with the oolemma E) The sperm tail is shed
Answer: C
Capacitation is a series of biochemical and biophysical changes that sperm undergo in the female reproductive tract, lasting approximately 5–6 hours in humans. It involves cholesterol efflux from the sperm membrane, increased membrane fluidity, changes in ion channels, and protein tyrosine phosphorylation. These changes enable the sperm to undergo the acrosome reaction (capacitation is a prerequisite) and develop hyperactivated motility.
📘 Q65 (Endocrinology) — Which of the following hormones is primarily responsible for the development of the male internal genitalia (epididymis, vas deferens, seminal vesicles) during fetal development? A) Testosterone B) Dihydrotestosterone (DHT) C) Anti-Müllerian hormone (AMH) D) Oestradiol E) Progesterone
Answer: A
Testosterone, secreted by fetal Leydig cells under the influence of hCG and later fetal LH, stimulates differentiation of the Wolffian ducts into the epididymis, vas deferens, and seminal vesicles. DHT (converted from testosterone by 5α-reductase) is responsible for external genitalia development (penis, scrotum). AMH from Sertoli cells causes regression of Müllerian ducts. This understanding is fundamental to disorders of sex development.
📘 Q66 (Physiology) — Which of the following describes the ovarian reserve? A) The number of antral follicles in both ovaries at any given time B) The total number of primordial follicles remaining in the ovaries C) The number of oocytes that will ovulate in a woman's lifetime D) The volume of the ovarian stroma E) The serum level of anti-Müllerian hormone (AMH)
Answer: B
The ovarian reserve refers to the total pool of primordial follicles present in the ovaries. This pool is established in fetal life (approximately 6–7 million at 20 weeks' gestation) and declines progressively through atresia and ovulation to about 1–2 million at birth, 300,000–500,000 at menarche, and <1,000 at menopause. AMH is a serum marker of ovarian reserve but is not the definition itself.
📘 Q67 (Physiology) — Which of the following is the mechanism by which the zona pellucida prevents polyspermy during fertilisation? A) The fast block depolarises the sperm plasma membrane B) The cortical reaction modifies ZP2 and ZP3, preventing further sperm binding C) The acrosome reaction of the first sperm destroys all other sperm D) Oocyte factors chemotactically repel additional sperm E) The perivitelline space fills with proteoglycans that trap sperm
Answer: B
After sperm fusion, cortical granules release enzymes that cleave ZP2 and ZP3 glycoproteins, hardening the zona pellucida and preventing additional sperm from binding or penetrating. This is the slow block to polyspermy (occurring within minutes). A fast block (depolarisation of the oolemma) occurs within seconds but is less well-characterised in humans. Polyspermy is lethal to the embryo.
📘 Q68 (Endocrinology) — Which of the following best describes the role of placental corticotrophin-releasing hormone (CRH) in human pregnancy? A) It suppresses the maternal HPA axis throughout pregnancy B) It is produced in the hypothalamus and regulates placental function C) Its levels rise exponentially towards term and contribute to the timing of parturition D) It stimulates fetal ACTH but has no effect on the maternal pituitary E) It decreases in the third trimester to allow labour to occur
Answer: C
Placental CRH is structurally identical to hypothalamic CRH but is produced by the syncytiotrophoblast and decidua. Its levels rise exponentially throughout pregnancy, peaking at term. Placental CRH stimulates fetal ACTH and cortisol production, which in turn upregulates placental CRH — a positive feedback loop. This "placental clock" is implicated in the timing of parturition and is altered in preterm labour.
📘 Q69 (Physiology) — A woman at 38 weeks gestation experiences supine hypotensive syndrome. Which of the following best describes the mechanism? A) Decreased heart rate due to increased vagal tone B) Compression of the inferior vena cava by the gravid uterus, reducing venous return C) Compression of the abdominal aorta by the uterus, increasing afterload D) Increased venous return causing bradycardia E) Uterine contractions reducing placental blood flow
Answer: B
Supine hypotensive syndrome occurs when the gravid uterus compresses the inferior vena cava in the supine position, reducing venous return and cardiac output. This causes hypotension, pallor, sweating, and sometimes syncope. It is more common after 20 weeks' gestation and is relieved by turning the woman onto her left lateral side (displacing the uterus off the vena cava).
📘 Q70 (Physiology) — Which of the following best describes the difference between theca interna and granulosa cells in terms of steroidogenic enzyme expression? A) Theca cells express aromatase; granulosa cells express 17α-hydroxylase B) Theca cells express 17α-hydroxylase and 3β-HSD; granulosa cells express aromatase and 17β-HSD C) Both cell types express all steroidogenic enzymes equally D) Granulosa cells express 17α-hydroxylase; theca cells express aromatase E) Neither cell type expresses 3β-HSD
Answer: B
Theca interna cells express the enzymes for androgen synthesis: CYP17A1 (17α-hydroxylase/17,20-lyase) and 3β-HSD, allowing conversion of cholesterol to androstenedione. Granulosa cells do not express CYP17A1 but express aromatase (CYP19A1) and 17β-HSD to convert androstenedione to oestradiol and oestrone. This differential expression is the basis of the two-cell, two-gonadotrophin model.
📘 Q71 (Endocrinology) — Which of the following hormones shows an episodic pulsatile pattern of secretion with the highest frequency in the early morning? A) Prolactin B) Cortisol C) Melatonin D) Testosterone E) FSH
Answer: D
Testosterone in males follows a circadian rhythm with peak levels in the early morning (around 4–8 AM) and nadir in the evening. This is driven by the circadian pattern of LH secretion. In women, testosterone also shows some diurnal variation but to a lesser extent. Cortisol also peaks in the early morning, but the question specifically asks about pulsatile secretion with highest frequency in early morning, and of the given options, testosterone is the best answer as LH/testosterone pulses are most robust in the morning.
📘 Q72 (Physiology) — Which of the following is the correct sequence of events immediately following ovulation? A) The ruptured follicle collapses, forms the corpus haemorrhagicum, then the corpus luteum, then the corpus albicans if no pregnancy occurs B) The ruptured follicle directly becomes the corpus albicans C) The oocyte re-enters the follicle after ovulation D) The follicle wall immediately undergoes apoptosis E) The ovulated oocyte enters the peritoneal cavity directly
Answer: A
After ovulation, the ruptured follicle collapses and fills with blood, forming the corpus haemorrhagicum. Under LH stimulation, granulosa and theca cells luteinise (enlarge and accumulate lipid) to form the corpus luteum. If pregnancy does not occur, the corpus luteum regresses after 14 days and becomes the hyalinised corpus albicans. If pregnancy occurs, hCG rescues the corpus luteum.
📘 Q73 (Physiology) — In the maternal renal system, which of the following hormones increases during pregnancy, leading to enhanced sodium and water retention? A) Atrial natriuretic peptide (ANP) B) Aldosterone C) Progesterone D) Dopamine E) Brain natriuretic peptide (BNP)
Answer: B
Aldosterone levels increase several-fold during pregnancy due to activation of the renin–angiotensin–aldosterone system (RAAS). Oestrogen stimulates hepatic angiotensinogen synthesis, and the reduced systemic vascular resistance activates renin release. This aldosterone elevation promotes renal sodium and water retention, contributing to the 40–50% increase in plasma volume despite the natriuretic effect of progesterone (which competes with aldosterone at the mineralocorticoid receptor).
📘 Q74 (Physiology) — Which of the following is the primary source of oestradiol during the early follicular phase of the menstrual cycle? A) The corpus luteum of the previous cycle B) The dominant (Graafian) follicle C) Small antral follicles undergoing recruitment D) The adrenal cortex E) Peripheral conversion of androgens in adipose tissue
Answer: C
In the early follicular phase, a cohort of small antral follicles (2–5 mm) are recruited under the influence of rising FSH. These follicles produce increasing amounts of oestradiol, which feeds back to suppress FSH. Eventually, one follicle becomes dominant. The corpus luteum is the main source of oestradiol in the luteal phase, not the follicular phase. Adipose tissue contributes to oestrogen production but is not the primary source.
📘 Q75 (Endocrinology) — A woman has a serum prolactin level of 2500 mIU/L (normal <500). Which of the following medications is most likely to cause this degree of hyperprolactinaemia? A) Metformin B) Domperidone C) Levothyroxine D) Oral contraceptive pill E) Omeprazole
Answer: B
Domperidone is a dopamine D2 receptor antagonist used as an antiemetic and galactagogue. By blocking the tonic inhibitory effect of dopamine on pituitary lactotrophs, it causes hyperprolactinaemia. Other common causes include antipsychotics (haloperidol, risperidone), metoclopramide, and verapamil. The degree of prolactin elevation depends on the drug's potency and dose.
📘 Q76 (Physiology) — Which of the following correctly describes the process of decidualisation? A) Transformation of endometrial stromal cells into specialised secretory cells under the influence of progesterone B) Proliferation of endometrial glands under oestradiol stimulation C) Sloughing of the endometrium during menstruation D) Invasion of the endometrium by syncytiotrophoblast E) Formation of the corpus luteum from the ruptured follicle
Answer: A
Decidualisation refers to the transformation of endometrial stromal fibroblasts into specialised decidual cells under the influence of progesterone following ovulation. These cells become enlarged, polygonal, and rich in glycogen and lipids. They secrete factors important for implantation and pregnancy maintenance (prolactin, IGFBP-1). Decidualisation begins in the luteal phase and is essential for establishing the maternal–fetal interface.
📘 Q77 (Endocrinology) — In the context of the hypothalamic–pituitary–gonadal (HPG) axis, which of the following statements about inhibin is correct? A) Inhibin A is secreted by granulosa cells of developing follicles; inhibin B is secreted by the corpus luteum B) Both inhibin A and inhibin B are secreted only by the corpus luteum C) Inhibin A is secreted by the corpus luteum; inhibin B is secreted by developing follicles D) Inhibin B selectively suppresses LH secretion E) Inhibin levels are highest during menstruation
Answer: C
Inhibin A is predominantly secreted by the corpus luteum and placenta, while inhibin B is predominantly secreted by granulosa cells of developing antral follicles. Both suppress pituitary FSH secretion via negative feedback (inhibin B in the follicular phase, inhibin A in the luteal phase). Inhibin levels are lowest at menses and peak in the mid-luteal phase. Activin, in contrast, stimulates FSH secretion.
📘 Q78 (Physiology) — During the second stage of labour, which of the following describes the Ferguson reflex? A) Contraction of the uterus triggered by oxytocin release in response to cervical distension B) Release of prolactin in response to nipple stimulation C) Involuntary maternal pushing effort stimulated by fetal head descent D) Contraction of the abdominal muscles during the second stage E) Relaxation of the pelvic floor muscles in response to pressure
Answer: A
The Ferguson reflex is a neuroendocrine reflex wherein distension of the cervix and upper vagina during the second stage of labour stimulates afferent sensory signals to the hypothalamus, triggering oxytocin release from the posterior pituitary. This oxytocin surge augments uterine contractions, providing a positive feedback loop that continues until delivery. This reflex is enhanced by upright positioning and is diminished by epidural analgesia.
📘 Q79 (Physiology) — Which of the following best describes the maternal metabolic adaptation of increased lipolysis during pregnancy? A) It is mediated by insulin and promotes fat storage B) It is mediated by hPL and provides an alternative energy source, sparing glucose for the fetus C) It causes maternal ketoacidosis in all pregnancies D) It reduces the availability of free fatty acids to the fetus E) It is suppressed by placental growth hormone
Answer: B
Human placental lactogen (hPL) and placental growth hormone promote maternal lipolysis, particularly in the second half of pregnancy. This increases circulating free fatty acids and glycerol, which the mother can use as energy, thereby sparing glucose for the fetus. This adaptation, combined with insulin resistance, ensures a continuous glucose supply to the fetus while allowing the mother to use alternative fuels.
📘 Q80 (Endocrinology) — In the adrenal cortex, which enzyme is unique to the zona glomerulosa and essential for aldosterone synthesis? A) 17α-hydroxylase (CYP17A1) B) 11β-hydroxylase (CYP11B1) C) Aldosterone synthase (CYP11B2) D) 21-hydroxylase (CYP21A2) E) 3β-hydroxysteroid dehydrogenase (3β-HSD)
Answer: C
Aldosterone synthase (CYP11B2) is expressed exclusively in the zona glomerulosa and catalyses the final steps of aldosterone synthesis: conversion of 11-deoxycorticosterone to corticosterone, and corticosterone to aldosterone. CYP11B1 (11β-hydroxylase) is expressed in the zona fasciculata and converts 11-deoxycortisol to cortisol. CYP17A1 is absent in the zona glomerulosa, which is why this zone cannot produce cortisol or sex steroids.
📘 Q81 (Physiology) — Which of the following best describes the effect of progesterone on the maternal respiratory system? A) It decreases the sensitivity of the respiratory centre to CO₂ B) It increases the sensitivity of the respiratory centre to CO₂, leading to hyperventilation C) It has no effect on respiratory function D) It suppresses the cough reflex E) It causes bronchoconstriction
Answer: B
Progesterone acts as a direct respiratory stimulant, increasing the sensitivity of the medullary respiratory centre to CO₂. This results in chronic hyperventilation in pregnancy, with increased tidal volume and minute ventilation. The resulting respiratory alkalosis (low PaCO₂, 28–32 mmHg) is a normal physiological adaptation that facilitates CO₂ transfer from the fetus to the mother.
📘 Q82 (Physiology) — Which of the following cells of the testis is functionally analogous to the ovarian granulosa cell? A) Leydig cell B) Sertoli cell C) Spermatogonium D) Peritubular myoid cell E) Spermatid
Answer: B
Sertoli cells in the testis are functionally analogous to granulosa cells in the ovary. Both are somatic cells that support gametogenesis, respond to FSH (via FSH receptors), produce inhibin, provide nutrients to developing gametes, and form part of the blood–testis or blood–follicle barrier. Leydig cells are analogous to theca interna cells, producing androgens under LH stimulation.
📘 Q83 (Physiology) — A woman presents with primary infertility and oligomenorrhoea. An ultrasound shows polycystic ovaries. Laboratory findings show elevated LH:FSH ratio. Which of the following best describes the underlying pathophysiology of polycystic ovary syndrome (PCOS)? A) Increased GnRH pulse frequency favouring LH over FSH secretion B) Decreased GnRH pulse frequency favouring FSH over LH secretion C) Primary ovarian failure with low AMH D) Hyperprolactinaemia causing anovulation E) 21-Hydroxylase deficiency
Answer: A
In PCOS, reduced hypothalamic sensitivity to progesterone negative feedback results in increased GnRH pulse frequency. Rapid GnRH pulses preferentially stimulate LH secretion (with relative suppression of FSH), leading to an elevated LH:FSH ratio (>2:1). The relative FSH deficiency impairs follicular maturation, while high LH stimulates excess androgen production from theca cells, contributing to the clinical features of hyperandrogenism.
📘 Q84 (Endocrinology) — Which of the following correctly describes the effect of maternal thyroid hormones on fetal neurodevelopment? A) Maternal T4 crosses the placenta and is converted to T3 in fetal brain tissue B) Maternal T3 crosses the placenta and directly stimulates fetal brain development C) The fetal thyroid is fully functional by 8 weeks' gestation D) Maternal hypothyroidism has no effect on fetal neurodevelopment E) TSH from the mother directly stimulates the fetal thyroid
Answer: A
Maternal T4 crosses the placenta and is converted to T3 by type 2 iodothyronine deiodinase (D2) in fetal brain tissue. This T3 is essential for neuronal migration, myelination, and synaptogenesis during the first and second trimesters, before the fetal thyroid becomes functional around 12–14 weeks. Maternal hypothyroidism, particularly in early pregnancy, is associated with impaired neurocognitive development in the offspring.
📘 Q85 (Physiology) — Which of the following is the primary determinant of the sex of the embryo at fertilisation? A) The number of X chromosomes in the oocyte B) Whether the fertilising sperm carries an X or a Y chromosome C) The presence of the SRY gene on the X chromosome D) The hormonal environment of the maternal uterus E) The number of oocytes released at ovulation
Answer: B
All oocytes carry an X chromosome. The sex of the embryo is determined by whether the fertilising sperm contributes an X chromosome (46,XX, female) or a Y chromosome (46,XY, male). The SRY gene on the Y chromosome encodes the testis-determining factor, which drives the undifferentiated gonad to develop into a testis. Without SRY, the default pathway is ovarian development.
📘 Q86 (Physiology) — Which of the following statements about anti-Müllerian hormone (AMH) is correct? A) AMH is secreted by Leydig cells and stimulates Wolffian duct development B) AMH is secreted by Sertoli cells and causes regression of Müllerian ducts in male fetuses C) AMH is secreted by granulosa cells and stimulates follicular growth D) AMH levels increase after menopause E) AMH is a product of the placenta that maintains pregnancy
Answer: B
AMH is a glycoprotein hormone belonging to the TGF-β family. In male fetuses, Sertoli cells secrete AMH from approximately 7–8 weeks' gestation, causing regression of the Müllerian ducts (which would otherwise form the uterus, fallopian tubes, and upper vagina). In females, AMH is secreted by granulosa cells of preantral and small antral follicles and is used as a marker of ovarian reserve.
📘 Q87 (Physiology) — In the maternal gastrointestinal system during pregnancy, which of the following changes is most commonly observed? A) Increased gastric acid secretion B) Decreased intestinal transit time due to increased motility C) Relaxation of the lower oesophageal sphincter due to progesterone, contributing to reflux D) Increased absorption of iron and calcium only E) Increased appetite exclusively in the first trimester
Answer: C
Progesterone causes smooth muscle relaxation throughout the gastrointestinal tract, including relaxation of the lower oesophageal sphincter, which predisposes to gastro-oesophageal reflux and heartburn. Progesterone also reduces gastric and intestinal motility (causing constipation). Gastric acid secretion is generally unchanged or slightly decreased. The enlarging uterus also compresses the stomach, exacerbating symptoms.
📘 Q88 (Endocrinology) — Which of the following statements best describes the role of androgens in normal female physiology? A) Androgens have no physiological role in women B) Testosterone is primarily produced by the adrenal glands and serves as a precursor for oestrogen synthesis C) Androgens are responsible for breast development D) DHEA-S is produced exclusively by the ovaries E) Androgens suppress gonadotrophin secretion in women more effectively than in men
Answer: B
In women, approximately 50% of testosterone is derived from peripheral conversion of androstenedione, 25% from the ovary, and 25% from the adrenal gland. DHEA-S is produced primarily by the adrenal zona reticularis. Androgens serve as precursors for oestrogen synthesis and contribute to libido, bone health, and muscle mass. Breast development is driven by oestrogen, not androgens.
📘 Q89 (Physiology) — Which of the following best describes the mechanism of lactational amenorrhoea? A) Suckling stimulates prolactin, which directly suppresses ovarian function B) Suckling inhibits GnRH pulsatility, reducing LH and FSH secretion and causing anovulation C) Prolactin directly destroys ovarian follicles D) Oxytocin released during suckling suppresses gonadotrophins E) Breastfeeding depletes maternal energy stores, causing hypothalamic amenorrhoea
Answer: B
Lactational amenorrhoea is primarily mediated by suckling-induced hyperprolactinaemia, which suppresses hypothalamic GnRH secretion by increasing opioidergic and dopaminergic tone. This reduces LH pulse frequency and amplitude, preventing ovulation and follicular development. The degree of suppression correlates with breastfeeding frequency and intensity. When suckling decreases, GnRH pulsatility recovers, and menstruation resumes.
📘 Q90 (Endocrinology) — Which of the following statements about the enzyme 5α-reductase is correct? A) It converts testosterone to oestradiol B) It converts testosterone to dihydrotestosterone (DHT) C) It converts androstenedione to oestrone D) It is expressed only in the prostate gland E) It is inhibited by FSH
Answer: B
5α-Reductase is an intracellular enzyme that irreversibly converts testosterone to the more potent androgen dihydrotestosterone (DHT). DHT has 2–3 times higher affinity for the androgen receptor than testosterone. Two isoforms exist: type 1 (skin, liver) and type 2 (external genitalia, prostate). 5α-Reductase deficiency causes ambiguous genitalia in males (pseudohermaphroditism) with normal Wolffian structures.
📘 Q91 (Physiology) — Which of the following is the primary mechanism by which oestradiol exerts negative feedback on FSH during the mid-follicular phase? A) Direct inhibition of FSH synthesis at the pituitary B) Slowing GnRH pulse frequency C) Increasing inhibin A secretion D) Suppressing kisspeptin expression in the arcuate nucleus E) Downregulating pituitary GnRH receptors
Answer: B
During the mid-follicular phase, oestradiol exerts negative feedback primarily by slowing GnRH pulse frequency from the hypothalamus. This favours the secretion of LH over FSH from the pituitary, as slower GnRH pulses enhance LH β-subunit synthesis while faster pulses favour FSH. Additionally, rising inhibin B from the dominant follicle directly suppresses pituitary FSH secretion.
📘 Q92 (Physiology) — Which of the following is the most accurate description of the maternal renal handling of glucose in pregnancy? A) The renal threshold for glucose increases, making glycosuria rare B) The renal threshold for glucose decreases, so glycosuria may occur even with normal blood glucose C) Glucose is actively secreted by the renal tubules in pregnancy D) Glycosuria in pregnancy always indicates gestational diabetes E) The kidneys reabsorb less sodium but more glucose in pregnancy
Answer: B
The renal threshold for glucose decreases in pregnancy due to increased GFR and reduced tubular reabsorptive capacity, so glycosuria (including on dipstick testing) is common in normal pregnancy and does not necessarily indicate hyperglycaemia. However, persistent or heavy glycosuria warrants formal glucose tolerance testing to exclude gestational diabetes mellitus.
📘 Q93 (Physiology) — During the mid-cycle LH surge, which of the following changes occurs in the dominant follicle? A) The oocyte completes meiosis II before ovulation B) Cumulus expansion occurs, and the oocyte resumes meiosis I C) Theca cells begin to secrete progesterone, and the oocyte arrests in prophase I D) Granulosa cells undergo apoptosis E) The follicle wall thickens to prevent rupture
Answer: B
The LH surge triggers several key events: (1) resumption of oocyte meiosis (from prophase I arrest to metaphase II); (2) cumulus expansion (mucification) — the cumulus cells secrete hyaluronic acid, expanding the cumulus mass; (3) luteinisation of granulosa cells, initiating progesterone secretion; and (4) production of proteolytic enzymes that weaken the follicle wall. Ovulation occurs approximately 36–40 hours later.
📘 Q94 (Endocrinology) — Which of the following statements about the enzyme aromatase is correct? A) It is inhibited by FSH in granulosa cells B) It converts cholesterol to pregnenolone C) It catalyses the conversion of androgens to oestrogens D) It is expressed only in the ovary E) It requires LH for its activation in granulosa cells
Answer: C
Aromatase (CYP19A1) catalyses the conversion of androstenedione to oestrone and testosterone to oestradiol. It is expressed in granulosa cells of the ovary, placental syncytiotrophoblast, adipose tissue, bone, brain, and skin. In granulosa cells, aromatase expression and activity are stimulated by FSH via the cAMP pathway. Aromatase inhibitors (e.g. letrozole, anastrozole) are used in breast cancer treatment and ovulation induction.
📘 Q95 (Physiology) — Which of the following is the primary function of the fetal zone of the fetal adrenal gland? A) Producing cortisol for fetal lung maturation B) Producing aldosterone for fetal sodium balance C) Producing DHEA-S as a substrate for placental oestrogen synthesis D) Producing catecholamines for fetal stress responses E) Producing testosterone for male genital development
Answer: C
The fetal zone of the fetal adrenal gland is a distinct inner layer that comprises 80–90% of the fetal adrenal and produces large quantities of DHEA-S. This DHEA-S is converted by the placenta (via 16α-hydroxylation in the fetal liver and then aromatisation) to oestriol, the predominant oestrogen of pregnancy. This pathway — the fetal–placental unit — is essential for pregnancy maintenance.
📘 Q96 (Physiology) — Which of the following hormonal changes is diagnostic of menopause? A) Elevated oestradiol with suppressed FSH B) Elevated FSH (>25 IU/L) and low oestradiol (<100 pmol/L) C) Elevated prolactin with low LH D) Low FSH with elevated progesterone E) Elevated LH alone is sufficient for diagnosis
Answer: B
Menopause is defined retrospectively after 12 months of amenorrhoea and is characterised by ovarian follicular depletion. This results in low oestradiol (loss of negative feedback) and markedly elevated FSH (>25–40 IU/L, often >40 IU/L). LH is also elevated but to a lesser degree. FSH is more reliable than LH because inhibin (which selectively suppresses FSH) is also depleted. The FSH rise precedes menopausal symptoms.
📘 Q97 (Physiology) — Which of the following best describes the mechanism by which the fetus acquires maternal IgG antibodies during pregnancy? A) Passive diffusion across the syncytiotrophoblast B) Active transport via Fc neonatal receptors (FcRn) on syncytiotrophoblast C) Ingestion of amniotic fluid containing maternal antibodies D) Transfer across the chorion only in the third trimester E) Direct passage through umbilical vessels
Answer: B
Maternal IgG is actively transported across the syncytiotrophoblast via neonatal Fc receptors (FcRn) in a process that begins around 13–16 weeks' gestation and increases exponentially towards term. This provides the neonate with passive immunity until its own immune system matures. IgA and IgM do not cross the placenta. The transferred IgG protects against infections in the first months of life.
📘 Q98 (Endocrinology) — A patient with Cushing syndrome is found to have an ACTH-independent source of hypercortisolism. Which of the following is the most likely aetiology? A) Pituitary ACTH-secreting adenoma (Cushing disease) B) Ectopic ACTH secretion from a small-cell lung carcinoma C) Adrenal adenoma D) CRH-secreting hypothalamic tumour E) Exogenous corticosteroid use
Answer: C
ACTH-independent Cushing syndrome implies that cortisol is produced autonomously by the adrenal cortex without ACTH stimulation. An adrenal adenoma (or carcinoma) is the most common cause, with suppressed ACTH levels. Pituitary (Cushing disease) and ectopic ACTH sources are ACTH-dependent. Exogenous corticosteroid use is iatrogenic Cushing syndrome but is also ACTH-independent via negative feedback.
📘 Q99 (Physiology) — Which of the following changes in the maternal cardiovascular system persists for the longest duration after delivery? A) Increased cardiac output returns to normal within 24 hours B) Systemic vascular resistance remains low for 6 months C) The increase in plasma volume resolves by 2 weeks postpartum D) Cardiac output remains elevated for at least 6 months postpartum in some women E) Heart rate returns to pre-pregnancy values within 48 hours
Answer: D
Cardiovascular changes of pregnancy do not resolve immediately after delivery. While some parameters normalise quickly (heart rate, blood pressure within days), cardiac output may remain elevated for weeks to months. Stroke volume increases further immediately postpartum due to autotransfusion from the contracted uterus. Most haemodynamic parameters return to non-pregnant levels by 6–12 weeks, but some studies show subtle changes persisting up to 6 months.
📘 Q100 (Physiology) — Which of the following is the final step in the biosynthesis of oestradiol from androstenedione in the ovary? A) Aromatisation of androstenedione to oestrone B) Reduction of oestrone to oestradiol by 17β-hydroxysteroid dehydrogenase (17β-HSD) C) Hydroxylation of androstenedione at the C19 position D) Conversion of testosterone to oestradiol by aromatase E) Sulphation of oestradiol by sulphotransferase
Answer: B
The final step in oestradiol biosynthesis is the reduction of oestrone to oestradiol by 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) in granulosa cells. Alternatively, aromatase can convert testosterone directly to oestradiol. However, the predominant pathway involves androstenedione → oestrone (via aromatase) → oestradiol (via 17β-HSD1). 17β-HSD2 in the endometrium inactivates oestradiol by converting it back to oestrone.