Reproductive Physiology — MCQs
On this page
A 32-year-old pregnant woman at 28 weeks gestation with type 1 diabetes presents with recurrent severe hypoglycemia despite reducing her insulin dose. Her insulin requirements have decreased by 40% over the past week. She reports decreased fetal movement. Fetal ultrasound shows intrauterine fetal demise. Evaluate the physiological mechanism explaining her changing insulin requirements in the context of pregnancy loss.
In a primary spermatocyte, what is the chromosome number and sex chromosome composition?
What is the peak level of Luteinizing Hormone (LH) required for ovulation?
What is the pH of the vagina during reproductive life?
The onset of the luteinizing hormone (LH) surge precedes ovulation by approximately how many hours?
What is the precursor for the synthesis of testosterone?
Recruitment of follicles is caused by?
What is the sensitivity of uterine musculature?
What is the efferent pathway for the milk ejection reflex?
Arrange the following in sequential order of their involvement in estrogen synthesis: Progesterone, Androgen in granulosa cell, Androgen in theca cell, Aromatase?
Reproductive Physiology Indian Medical PG Practice Questions and MCQs
Question 11: A 32-year-old pregnant woman at 28 weeks gestation with type 1 diabetes presents with recurrent severe hypoglycemia despite reducing her insulin dose. Her insulin requirements have decreased by 40% over the past week. She reports decreased fetal movement. Fetal ultrasound shows intrauterine fetal demise. Evaluate the physiological mechanism explaining her changing insulin requirements in the context of pregnancy loss.
- A. Increased maternal growth hormone from pituitary compensation for fetal loss
- B. Placental glucose consumption cessation leading to maternal hyperglycemia compensation
- C. Maternal thyroid hormone surge causing enhanced glucose utilization
- D. Increased maternal cortisol from stress of fetal loss improving insulin sensitivity
- E. Loss of placental lactogen and other diabetogenic hormones that normally increase insulin resistance (Correct Answer)
Explanation: ***Loss of placental lactogen and other diabetogenic hormones that normally increase insulin resistance*** - Normal pregnancy induces **insulin resistance** via the production of **human placental lactogen (hPL)**, cortisol, and progesterone to ensure continuous glucose supply to the fetus. - Upon **intrauterine fetal demise**, the placenta stops producing these hormones, leading to a sudden **increase in insulin sensitivity** and a drastic drop in insulin requirements, often manifesting as severe **hypoglycemia**. *Increased maternal growth hormone from pituitary compensation for fetal loss* - Maternal **pituitary growth hormone** is actually suppressed during pregnancy as **placental growth hormone** takes over its role. - Growth hormone is a **diabetogenic hormone**; its increase would cause hyperglycemia rather than the recurrent hypoglycemia seen in this patient. *Placental glucose consumption cessation leading to maternal hyperglycemia compensation* - While the fetus and placenta consume glucose, their loss of function is overshadowed by the more significant drop in **hormone-mediated insulin resistance**. - The net clinical effect of placental failure in a diabetic mother is almost always a **decrease in glucose levels**, not compensatory hyperglycemia. *Maternal thyroid hormone surge causing enhanced glucose utilization* - Pregnancy naturally increases **thyroid-binding globulin**, but a sudden surge of thyroid hormone is not a physiological response to fetal demise. - While hyperthyroidism can affect metabolism, it typically worsens **glucose intolerance** rather than causing the 40% reduction in insulin needs observed here. *Increased maternal cortisol from stress of fetal loss improving insulin sensitivity* - **Cortisol** is a stress hormone that promotes **gluconeogenesis** and increases insulin resistance, which would raise blood sugar levels. - The stress of fetal loss would theoretically increase insulin requirements; therefore, it cannot explain the **improved insulin sensitivity** and hypoglycemia reported.
Question 12: In a primary spermatocyte, what is the chromosome number and sex chromosome composition?
- A. 23, X
- B. 23, Y
- C. 46, XY (Correct Answer)
- D. None of the above
Explanation: ### Explanation **Concept Overview:** Spermatogenesis is a sequential process of cell differentiation and division. It begins with **Spermatogonia** (diploid, 46 XY), which undergo mitotic division to maintain their population and differentiate into **Primary Spermatocytes**. Because primary spermatocytes are formed via mitosis and have not yet completed the first meiotic division, they remain **diploid**. **Why Option C is Correct:** A primary spermatocyte contains the full complement of genetic material required to initiate meiosis. It has **46 chromosomes (2n)** and a **XY sex chromosome composition**. Although it undergoes DNA replication (becoming 4n in DNA content) just before meiosis I, the chromosome number remains 46 until the cell actually divides. **Why Other Options are Incorrect:** * **Options A & B (23, X or 23, Y):** These represent the **haploid (n)** state. This reduction in chromosome number only occurs *after* the completion of Meiosis I. Secondary spermatocytes, spermatids, and mature spermatozoa are haploid, containing either an X or a Y chromosome, but not both. --- ### High-Yield NEET-PG Pearls: * **Primary Spermatocyte:** The largest germ cell in the seminiferous tubules. It stays in the **prophase of Meiosis I** for about 22 days (the longest stage). * **Secondary Spermatocyte:** Formed after Meiosis I. It is haploid (23, X or 23, Y) but has double the DNA amount (2c) compared to a spermatid. * **Spermiogenesis:** The transformation of a circular spermatid into a motile spermatozoon (no cell division involved). * **Blood-Testis Barrier:** Formed by tight junctions between **Sertoli cells**; it protects the primary spermatocytes (as they move into the adluminal compartment) from the immune system.
Question 13: What is the peak level of Luteinizing Hormone (LH) required for ovulation?
- A. 15 ng/ml
- B. 50 ng/ml
- C. 30 ng/ml
- D. 75 ng/ml (Correct Answer)
Explanation: **Explanation:** The correct answer is **75 ng/ml**. **Underlying Medical Concept:** Ovulation is triggered by the **LH surge**, a dramatic rise in Luteinizing Hormone levels caused by a switch from negative to positive feedback of Estrogen on the anterior pituitary. For ovulation to occur, the LH levels must rise significantly from a basal level of approximately 10–15 ng/ml to a peak of about **75 ng/ml**. This surge typically occurs 24–36 hours before the follicle ruptures. The high concentration of LH is essential to resume meiosis I in the oocyte, stimulate prostaglandin synthesis for follicular wall rupture, and initiate the luteinization of granulosa cells. **Analysis of Options:** * **A (15 ng/ml):** This represents the **basal level** of LH during the early follicular phase, which is insufficient to trigger ovulation. * **B (50 ng/ml):** While this indicates a rising level during the surge, it has not yet reached the physiological peak required for the ovulatory stimulus. * **C (30 ng/ml):** This is a mid-range value often seen just as the surge begins, but it is below the threshold for follicular rupture. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** Ovulation occurs **10–12 hours after the LH peak** and **24–36 hours after the LH surge begins**. * **The Trigger:** Estrogen must maintain a concentration of **>200 pg/ml for at least 48 hours** to trigger the LH surge (Positive Feedback). * **Urine Testing:** Ovulation predictor kits (OPKs) detect the rise in urinary LH, which precedes ovulation by about 12–24 hours. * **Meiosis:** The LH surge is responsible for the completion of **Meiosis I** (arrested in prophase) and the start of **Meiosis II** (arrested in metaphase).
Question 14: What is the pH of the vagina during reproductive life?
- A. Alkaline
- B. Acidic (Correct Answer)
- C. Neutral
- D. Variable
Explanation: **Explanation:** The vaginal pH during reproductive life is typically **acidic**, ranging between **3.8 and 4.5**. This acidity is a critical physiological defense mechanism. **Why the correct answer is right:** Under the influence of high **estrogen** levels during reproductive years, the vaginal epithelium thickens and accumulates **glycogen**. **Döderlein’s bacilli** (Lactobacillus species), which are the commensal flora of the vagina, ferment this glycogen into **lactic acid**. This process maintains a low pH, which inhibits the overgrowth of pathogenic bacteria and fungi, thereby preventing infections like bacterial vaginosis. **Why the other options are wrong:** * **Alkaline:** An alkaline pH (>4.5) is abnormal during reproductive years and is often a diagnostic sign of infections (e.g., Trichomoniasis or Bacterial Vaginosis). The vagina is only naturally alkaline before puberty and after menopause due to low estrogen and lack of Lactobacilli. * **Neutral:** A pH of 7.0 is not physiological for the vagina at any stage of life. * **Variable:** While pH can fluctuate slightly (e.g., it becomes more alkaline during menstruation or after intercourse due to the alkalinity of blood and semen), the baseline state remains consistently acidic. **High-Yield NEET-PG Pearls:** 1. **Estrogen Dependency:** The acidity of the vagina is directly proportional to estrogen levels. Therefore, the pH is **alkaline/neutral** in prepubertal girls and postmenopausal women. 2. **Amniotic Fluid:** In obstetrics, the **Nitrazine test** uses pH to detect the rupture of membranes; amniotic fluid is alkaline, turning the yellow nitrazine paper blue. 3. **Semen:** Seminal fluid is alkaline (pH 7.2–8.0) to neutralize the vaginal acidity and protect sperm.
Question 15: The onset of the luteinizing hormone (LH) surge precedes ovulation by approximately how many hours?
- A. 12 hours
- B. 24 hours
- C. 36 hours (Correct Answer)
- D. 48 hours
Explanation: ### Explanation **Correct Answer: C. 36 hours** **Medical Concept:** Ovulation is triggered by a dramatic rise in Luteinizing Hormone (LH), known as the **LH surge**. This surge is initiated by a positive feedback mechanism where high levels of sustained estrogen (produced by the dominant Graafian follicle) stimulate the anterior pituitary. The timing of ovulation relative to this surge is a high-yield distinction in physiology: * **Onset of LH Surge:** Ovulation occurs approximately **32 to 36 hours** after the initial rise in LH levels. * **Peak of LH Surge:** Ovulation occurs approximately **10 to 12 hours** after the LH peak (acrophase). **Analysis of Options:** * **A. 12 hours:** This is the interval between the **LH peak** and ovulation, not the onset of the surge. * **B. 24 hours:** While the surge lasts about 48 hours, 24 hours is an intermediate stage and does not represent the standard physiological onset-to-ovulation window. * **D. 48 hours:** This is the approximate total duration of the LH surge itself, but ovulation occurs before the surge completely subsides. **NEET-PG High-Yield Pearls:** 1. **Meiosis I Completion:** The LH surge is responsible for the primary oocyte completing Meiosis I and entering Meiosis II (arresting at Metaphase II) just before ovulation. 2. **Stigma Formation:** LH increases local prostaglandins and proteolytic enzymes (like collagenase), which weaken the follicular wall to form the "stigma" through which the ovum escapes. 3. **Urine LH Kits:** These kits detect the LH surge and are used clinically to predict the "fertile window," as ovulation will likely occur within the next 1–1.5 days. 4. **Mittelschmerz:** This refers to the mid-cycle pelvic pain some women experience during ovulation due to follicular fluid or blood irritating the peritoneum.
Question 16: What is the precursor for the synthesis of testosterone?
- A. Aldosterone
- B. Cholesterol
- C. Pregnenolone (Correct Answer)
- D. Cortisol
Explanation: **Explanation:** The correct answer is **Pregnenolone**. **Why Pregnenolone is correct:** In the steroidogenic pathway, **Cholesterol** is the initial parent compound. However, the first committed step in the synthesis of all steroid hormones (including testosterone) is the conversion of Cholesterol into **Pregnenolone** via the enzyme **Cholesterol side-chain cleavage enzyme (P450scc/Desmolase)**, located in the mitochondria. Pregnenolone serves as the immediate common precursor for progestogens, glucocorticoids, mineralocorticoids, and androgens. In the Leydig cells of the testes, Pregnenolone is converted to testosterone via either the $\Delta^5$ pathway (Dehydroepiandrosterone) or the $\Delta^4$ pathway (Progesterone). **Why other options are incorrect:** * **B. Cholesterol:** While cholesterol is the "starting material" or "parent molecule," Pregnenolone is the specific biosynthetic **precursor** that enters the steroid pathways. In medical exams, if both are listed, Pregnenolone is the more proximal precursor. * **A. Aldosterone & D. Cortisol:** These are end-products of the steroidogenic pathway in the adrenal cortex (mineralocorticoids and glucocorticoids, respectively). They are not precursors for testosterone; rather, they share the same initial precursor (Pregnenolone). **High-Yield Clinical Pearls for NEET-PG:** * **Rate-limiting step:** The transport of cholesterol into the mitochondria by the **StAR (Steroidogenic Acute Regulatory) protein** is the rate-limiting step in steroidogenesis. * **LH Action:** Luteinizing Hormone (LH) stimulates testosterone production by increasing the activity of Cholesterol Desmolase in Leydig cells. * **Potency:** Testosterone is converted to the more potent **Dihydrotestosterone (DHT)** by the enzyme **5-$\alpha$ reductase** in peripheral tissues (e.g., prostate, skin).
Question 17: Recruitment of follicles is caused by?
- A. LH
- B. FSH (Correct Answer)
- C. Inhibin β
- D. GnRH
Explanation: ### Explanation **Correct Answer: B. FSH (Follicle Stimulating Hormone)** **Mechanism of Follicular Recruitment:** Follicular development occurs in two distinct phases: the **gonadotropin-independent phase** (initial recruitment) and the **gonadotropin-dependent phase** (cyclic recruitment). * **Cyclic Recruitment:** During the late luteal phase of the previous menstrual cycle, progesterone and estrogen levels fall, leading to a "selective" rise in **FSH**. This rise in FSH rescues a cohort of antral follicles from atresia and recruits them for further growth. * FSH binds to receptors on granulosa cells, stimulating their proliferation and inducing the expression of aromatase enzymes, which are essential for estrogen production. **Analysis of Incorrect Options:** * **A. LH (Luteinizing Hormone):** LH is primarily responsible for the final maturation of the dominant follicle, the LH surge (triggering ovulation), and the maintenance of the corpus luteum. While it stimulates theca cells to produce androgens, it does not initiate the recruitment of the follicular cohort. * **C. Inhibin β:** Inhibin (specifically Inhibin B) is produced by granulosa cells and serves as a negative feedback signal to *inhibit* FSH secretion. It does not cause recruitment; rather, its rising levels help select the dominant follicle by suppressing FSH, leading to the atresia of smaller follicles. * **D. GnRH:** While GnRH is the master regulator that stimulates the pulsatile release of both FSH and LH from the anterior pituitary, it is the specific action of FSH on the ovary that directly causes follicular recruitment. **High-Yield Clinical Pearls for NEET-PG:** * **Inhibin B** is the primary marker of the **ovarian reserve** and antral follicle count (levels are highest in the early follicular phase). * **Inhibin A** is secreted by the **corpus luteum** (highest in the mid-luteal phase). * The "Window of Recruitment" occurs during the transition from the late luteal to the early follicular phase. * **Two-Cell, Two-Gonadotropin Theory:** LH acts on Theca cells (producing Androstenedione); FSH acts on Granulosa cells (converting Androstenedione to Estradiol via aromatase).
Question 18: What is the sensitivity of uterine musculature?
- A. Enhanced by progesterone
- B. Enhanced by estrogen
- C. Inhibited by estrogen
- D. Enhanced by estrogen and inhibited by progesterone (Correct Answer)
Explanation: The sensitivity of the uterine musculature (myometrium) to contractile stimuli, such as oxytocin and mechanical stretch, is regulated by the hormonal balance between estrogen and progesterone. ### **Explanation of the Correct Answer** **Option D** is correct because of the distinct physiological roles these steroids play on the myometrium: * **Estrogen (The Stimulator):** Estrogen increases the excitability of the myometrium. It achieves this by increasing the synthesis of **connexin-43** (gap junctions), which facilitates electrical coupling between muscle cells. It also upregulates the expression of **oxytocin receptors** and increases the resting membrane potential, making the uterus more "primed" for contraction. * **Progesterone (The Quiescent Factor):** Known as the "hormone of pregnancy," progesterone maintains uterine quiescence. It hyperpolarizes the myometrial cells, decreases the expression of gap junctions, and inhibits the synthesis of oxytocin receptors. This "progesterone block" is essential for preventing premature labor. ### **Analysis of Incorrect Options** * **Option A & C:** These are incorrect because they reverse the physiological roles. Progesterone decreases sensitivity (inhibits), while estrogen increases it (enhances). * **Option B:** While partially true, it is incomplete. The regulation of uterine tone is a dual mechanism involving the inhibitory effect of progesterone. ### **NEET-PG High-Yield Pearls** * **Ferguson Reflex:** This is the neuroendocrine reflex where cervical stretching leads to oxytocin release. Estrogen enhances this reflex by increasing oxytocin receptor density. * **Progesterone Withdrawal:** The onset of labor is often preceded by a functional withdrawal of progesterone, which tips the balance in favor of estrogen-driven contractions. * **Gap Junctions:** The sudden increase in gap junctions just before labor is the key histological change that allows the uterus to contract as a single functional syncytium.
Question 19: What is the efferent pathway for the milk ejection reflex?
- A. Prolactin
- B. Oxytocin (Correct Answer)
- C. ACTH
- D. Growth hormone
Explanation: ### Explanation The **Milk Ejection Reflex** (also known as the "Let-down reflex") is a neuroendocrine reflex initiated by the suckling stimulus. **1. Why Oxytocin is Correct:** When an infant suckles, tactile receptors on the nipple send afferent impulses via the somatic nerves to the **supraoptic and paraventricular nuclei** of the hypothalamus. This triggers the posterior pituitary to release **Oxytocin** into the bloodstream. Oxytocin acts as the **efferent hormone**, traveling to the breast where it causes contraction of the **myoepithelial cells** surrounding the alveoli. This squeeze forces milk from the alveoli into the lactiferous ducts and out through the nipple. **2. Why Other Options are Incorrect:** * **Prolactin:** While essential for lactation, Prolactin is responsible for **milk production and secretion** (synthesis) within the alveolar epithelium, not the physical ejection of milk. * **ACTH & Growth Hormone:** These hormones play a supportive (permissive) role in the development of mammary tissue and metabolic maintenance during lactation but are not part of the acute milk ejection reflex pathway. **3. Clinical Pearls for NEET-PG:** * **Conditioned Reflex:** Unlike milk production, milk ejection can be triggered by psychic stimuli (e.g., the sound of a baby crying) or inhibited by stress/pain (due to increased sympathetic activity). * **Uterine Contraction:** Oxytocin released during breastfeeding also causes uterine contractions (involution), helping the uterus return to its pre-pregnancy size and reducing postpartum hemorrhage. * **Dopamine Connection:** Prolactin is under tonic inhibition by **Dopamine** (Prolactin Inhibiting Hormone). Suckling inhibits dopamine, thereby increasing prolactin.
Question 20: Arrange the following in sequential order of their involvement in estrogen synthesis: Progesterone, Androgen in granulosa cell, Androgen in theca cell, Aromatase?
- A. Androgen in granulosa cell - Progesterone - Aromatase - Androgen in theca cell
- B. Progesterone - Androgen in theca cell - Aromatase - Androgen in granulosa cell
- C. Aromatase - Androgen in theca cell - Progesterone - Androgen in granulosa cell
- D. Progesterone - Androgen in theca cell - Androgen in granulosa cell - Aromatase (Correct Answer)
Explanation: This question tests your understanding of the **Two-Cell, Two-Gonadotropin Theory** of ovarian steroidogenesis. Estrogen synthesis requires the coordinated action of the Theca and Granulosa cells. ### **The Correct Sequence (Option D):** 1. **Progesterone:** In the **Theca cell**, Cholesterol is converted into Pregnenolone and then into **Progesterone**. 2. **Androgen in Theca cell:** Under the influence of **LH**, the Theca cell converts Progesterone into Androgens (mainly Androstenedione and Testosterone). Theca cells lack the enzyme aromatase, so they cannot produce estrogen themselves. 3. **Androgen in Granulosa cell:** These androgens diffuse across the basement membrane into the **Granulosa cell**. 4. **Aromatase:** Under the influence of **FSH**, the enzyme **Aromatase** in the Granulosa cell converts these androgens into Estrogens (Estradiol and Estrone). ### **Why Other Options are Incorrect:** * **Option A & C:** These are incorrect because Aromatase is the *final* enzymatic step in the pathway, not an intermediate or starting point. * **Option B:** This incorrectly places Aromatase before the entry of androgens into the granulosa cell. Aromatase acts *on* the androgens once they have arrived in the granulosa cell. ### **High-Yield NEET-PG Pearls:** * **LH** acts on **L**eiden/Theca cells (to produce androgens). * **FSH** acts on **G**ranulosa cells (to stimulate aromatase). * **Rate-limiting step:** The conversion of Cholesterol to Pregnenolone by the enzyme *Desmolase* (stimulated by LH). * **Theca cells** lack Aromatase; **Granulosa cells** lack 17α-hydroxylase (and thus cannot make androgens from progesterone).
Practice by Chapter
Male Reproductive Physiology
Practice Questions
Spermatogenesis and Sperm Function
Practice Questions
Female Reproductive Physiology
Practice Questions
Menstrual Cycle
Practice Questions
Ovulation and Fertilization
Practice Questions
Physiology of Pregnancy
Practice Questions
Parturition
Practice Questions
Lactation
Practice Questions
Sexual Differentiation and Development
Practice Questions
Reproductive Aging
Practice Questions
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free