Reproductive Physiology Practice Questions

Q: As menstruation ends, estrogen levels in the blood rise rapidly. What is the source of the estrogen?

Developing follicles. **Explanation:** The menstrual cycle is governed by the rhythmic fluctuation of hormones. The rise in estrogen immediately following menstruation marks the beginning of the **Follicular Phase** (Proliferative Phase). **1. Why "Developing Follicles" is correct:** As menstruation ends, the pituitary gland secretes **Follicle-Stimulating Hormone (FSH)**. FSH recruits a cohort of primordial follicles to grow. Within these developing follicles, the **Theca interna cells** produce androgens (androstenedione) under the influence of LH. These androgens then diffuse into the **Granulosa cells**, where the enzyme **aromatase** converts them into **Estradiol (Estrogen)**. This is known as the **"Two-Cell, Two-Gonadotropin" theory**. As the follicles grow, estrogen levels rise rapidly to repair the endometrium. **2. Why other options are incorrect:** * **Corpus Luteum:** This structure forms *after* ovulation (Luteal Phase). While it secretes estrogen, its primary product is progesterone. It regresses before menstruation begins, causing the initial drop in estrogen. * **Endometrium:** The endometrium is the *target* organ for estrogen, not the source. Estrogen causes the endometrium to proliferate (thicken). * **Stromal cells:** While ovarian stroma can produce small amounts of androgens, they are not the primary source of the rapid estrogen rise seen in the early-to-mid follicular phase. **High-Yield Clinical Pearls for NEET-PG:** * **Dominant Follicle:** The follicle with the highest density of FSH receptors becomes the "Graafian follicle" and produces the most estrogen. * **Positive Feedback:** When estrogen levels reach a threshold (approx. 200 pg/mL for 48 hours), it triggers the **LH surge**, leading to ovulation. * **Inhibin B:** Produced by granulosa cells in the follicular phase; it provides negative feedback to FSH.

Q: Corpus luteum formation occurs on which day of the menstrual cycle?

15th day. **Explanation:** The **Corpus Luteum** is a temporary endocrine structure formed from the remnants of the Graafian follicle immediately following ovulation. In a standard 28-day menstrual cycle, ovulation typically occurs on the **14th day** (triggered by the LH surge). Therefore, the transformation of the collapsed follicle into the corpus luteum (luteinization) begins on the **15th day**. * **Option A (15th Day):** This marks the beginning of the **Luteal Phase**. Under the influence of Luteinizing Hormone (LH), granulosa and theca cells proliferate and accumulate lipids (lutein) to secrete progesterone, which is essential for maintaining a potential pregnancy. * **Option B (22nd Day):** This is the period of peak corpus luteum activity. Progesterone levels reach their maximum around day 21–22, coinciding with the window of implantation. * **Option C (1st Day):** This represents the onset of menses (Follicular Phase), where the corpus luteum from the previous cycle has already degenerated into the corpus albicans. * **Option D (28th Day):** This is the end of the cycle. In the absence of hCG (pregnancy), the corpus luteum undergoes regression (luteolysis), leading to a drop in progesterone and the start of menstruation. **High-Yield NEET-PG Pearls:** 1. **Life Span:** The corpus luteum has a fixed functional lifespan of approximately **12–14 days** if fertilization does not occur. 2. **Hormone Secretion:** It secretes primarily **Progesterone**, but also Estrogen and Inhibin A. 3. **Rescue Mechanism:** If pregnancy occurs, **hCG** (produced by syncytiotrophoblasts) rescues the corpus luteum, maintaining it until the placenta takes over progesterone production (luteal-placental shift) at around 7–9 weeks.

Q: Levels of which of the following hormones are increased in post-menopausal women?

FSH. **Explanation:** The primary physiological hallmark of menopause is the depletion of ovarian follicles. As the number of follicles declines, there is a significant decrease in the production of **Estrogen** (specifically estradiol) and **Inhibin B**. Under normal physiological conditions, Estrogen and Inhibin exert negative feedback on the anterior pituitary and hypothalamus. When these levels drop during menopause, the negative feedback loop is lost. Consequently, the pituitary gland increases the secretion of **Follicle-Stimulating Hormone (FSH)** and Luteinizing Hormone (LH) in an attempt to stimulate the non-responsive ovaries. FSH levels rise more significantly and earlier than LH, making it the most sensitive biochemical marker for menopause. **Analysis of Options:** * **A. Estrogen:** Levels decrease significantly because the ovaries no longer produce functional follicles. * **C. Progesterone:** Levels decrease because ovulation ceases, meaning no corpus luteum is formed to produce progesterone. * **D. Cortisol:** This is an adrenal hormone. While aging affects the endocrine system, cortisol levels do not characteristically increase as a direct result of menopause. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Threshold:** An FSH level **>40 mIU/mL** is generally considered diagnostic of menopause in the clinical context of amenorrhea. * **Predominant Estrogen:** In post-menopausal women, **Estrone (E1)** becomes the dominant estrogen (produced via peripheral conversion of androstenedione in adipose tissue), replacing Estradiol (E2). * **LH/FSH Ratio:** In menopause, the FSH level is typically higher than the LH level (FSH > LH). * **First Sign:** The earliest biochemical change in the perimenopausal period is a decrease in **Inhibin B**, leading to a subtle rise in FSH.

Q: Which hormone shows no significant change in its levels throughout the menstrual cycle?

Activin. ### Explanation **Correct Option: A (Activin)** Activin is a member of the transforming growth factor-beta (TGF-β) superfamily. Unlike other reproductive hormones, **Activin levels remain relatively constant** throughout the menstrual cycle. Its primary role is to stimulate FSH synthesis and secretion and enhance the action of LH in the ovaries. While it plays a crucial role in the follicular phase by increasing FSH receptor expression on granulosa cells, its systemic concentration does not fluctuate significantly because it is widely expressed in various tissues and is regulated locally (paracrine/autocrine) by its binding protein, **follistatin**. **Why other options are incorrect:** * **Inhibin (B):** Shows significant fluctuations. **Inhibin B** peaks during the mid-follicular phase (secreted by antral follicles), while **Inhibin A** peaks during the mid-luteal phase (secreted by the corpus luteum). * **FSH (C):** Exhibits a distinct peak just before ovulation (the mid-cycle surge) and a secondary rise at the end of the luteal phase to recruit the next cohort of follicles. * **GnRH (D):** The pulse frequency and amplitude of GnRH change dramatically. It pulses faster in the follicular phase (to favor FSH/LH release) and slower in the luteal phase (due to progesterone inhibition). **High-Yield Clinical Pearls for NEET-PG:** * **Inhibin B** is the best biochemical marker for **ovarian reserve**. * **Activin** acts via serine/threonine kinase receptors, whereas most pituitary hormones use G-protein coupled receptors. * **Mnemonic for Inhibins:** Inhibin **B** is for **B**efore ovulation (follicular); Inhibin **A** is for **A**fter ovulation (luteal). * **Follistatin** is the specific antagonist that binds to and neutralizes Activin.

Q: Which hormone is involved in the milk secretion reflex?

Prolactin. **Explanation:** The process of lactation involves two distinct reflexes: **Milk Secretion (Production)** and **Milk Ejection (Let-down)**. 1. **Why Prolactin is Correct:** Prolactin, secreted by the **anterior pituitary**, is the primary hormone responsible for the **secretion and synthesis** of milk. When an infant suckles, tactile receptors on the nipple send signals to the hypothalamus, which inhibits Dopamine (Prolactin Inhibiting Factor). This leads to a surge in Prolactin, which acts on the alveolar epithelium of the mammary glands to stimulate milk production. 2. **Why Other Options are Incorrect:** * **Oxytocin:** This hormone is responsible for the **Milk Ejection Reflex** (Milk Let-down). It causes the contraction of **myoepithelial cells** surrounding the alveoli, squeezing out already secreted milk. It does not synthesize milk. * **Vasopressin (ADH):** Primarily involved in water reabsorption in the kidneys and vasoconstriction; it has no direct role in lactation. * **Progesterone:** During pregnancy, high levels of progesterone actually **inhibit** the action of prolactin on the breasts, preventing significant milk production until after delivery (when progesterone levels plummet). **High-Yield Clinical Pearls for NEET-PG:** * **Suckling Stimulus:** The strongest stimulus for both Prolactin and Oxytocin release. * **Galactorrhea:** Often caused by Prolactinomas or drugs that antagonize Dopamine (e.g., Metoclopramide, Antipsychotics). * **Lactational Amenorrhea:** High prolactin levels inhibit **GnRH pulsatility**, leading to suppressed LH/FSH and temporary infertility. * **Mnemonic:** **P**rolactin **P**roduces milk; **O**xyto-**C**in **C**ontracts (myoepithelial cells).

Q: Which one of the following androgens is not produced by Leydig cells of the testis?

Dihydrotestosterone. ### Explanation **1. Why Dihydrotestosterone (DHT) is the Correct Answer:** The Leydig cells of the testis are the primary site for the synthesis of androgens from cholesterol. However, they lack significant amounts of the enzyme **5α-reductase**. Dihydrotestosterone (DHT) is a potent metabolite of testosterone produced primarily in **peripheral tissues** (such as the prostate, skin, and hair follicles) through the action of 5α-reductase on testosterone. Therefore, while the testis produces the precursors, DHT itself is not a direct secretory product of Leydig cells. **2. Analysis of Incorrect Options:** * **Testosterone (A):** This is the principal androgen secreted by Leydig cells (approx. 95% of circulating testosterone). Its production is stimulated by Luteinizing Hormone (LH). * **Androstenedione (B) and Dehydroepiandrosterone (DHEA) (D):** These are intermediate weak androgens in the steroidogenic pathway. Leydig cells contain the necessary enzymes (like 3β-HSD and 17β-HSD) to synthesize these precursors before they are converted into testosterone. Small amounts of these are secreted directly into the bloodstream. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Potency:** DHT is the most potent natural androgen; it has a higher affinity for the androgen receptor than testosterone. * **Embryology:** Testosterone is responsible for the development of internal male genitalia (Wolffian duct derivatives), whereas **DHT** is essential for the development of **external male genitalia** and the prostate. * **Clinical Correlation:** 5α-reductase inhibitors (e.g., **Finasteride**) are used to treat Benign Prostatic Hyperplasia (BPH) and male pattern baldness by blocking the peripheral conversion of testosterone to DHT. * **Rate-limiting step:** The conversion of cholesterol to pregnenolone by the enzyme **Desmolase** (stimulated by LH) is the rate-limiting step in Leydig cell steroidogenesis.

Q: The ovulatory period corresponds to:

14 days before menstruation. **Explanation:** The menstrual cycle is divided into two main phases: the **Follicular Phase** (variable in length) and the **Luteal Phase** (constant in length). **1. Why Option A is Correct:** The luteal phase, which occurs after ovulation, is remarkably constant at **14 days** across almost all women. This is because the lifespan of the *corpus luteum* is fixed; if fertilization does not occur, it undergoes involution (luteolysis) exactly 14 days after its formation. Therefore, regardless of whether a cycle is 28, 35, or 21 days long, ovulation always occurs approximately 14 days **before** the onset of the next menstrual period. **2. Why Other Options are Incorrect:** * **Option B:** Menstruation marks the beginning of the follicular phase (Day 1), not the ovulatory period. * **Option C:** While an increase in basal body temperature (BBT) occurs due to the thermogenic effect of **Progesterone**, this rise happens *after* ovulation has already occurred. It is a retrospective indicator of ovulation, not the ovulatory period itself. * **Option D:** This is only true in a perfect 28-day cycle. In cycles of different lengths, the follicular phase varies, making "14 days after menstruation" an unreliable predictor. **Clinical Pearls for NEET-PG:** * **LH Surge:** The most reliable predictor of impending ovulation (occurs 24–36 hours before). * **Mittelschmerz:** Pelvic pain experienced by some women mid-cycle during ovulation. * **Spinnbarkeit Phenomenon:** Under estrogen influence, cervical mucus becomes thin, watery, and stretchy (like egg white) just before ovulation. * **Fern Test:** Estrogen causes "ferning" of cervical mucus; Progesterone (post-ovulation) disappears this pattern.

Q: Glucose is transported from the placenta to the fetus by which mechanism?

Facilitated diffusion. **Explanation:** The transport of glucose across the placenta is a high-yield concept in Maternal-Fetal Medicine. Glucose is the primary energy source for the fetus, and its transfer occurs via **Facilitated Diffusion**. **1. Why Facilitated Diffusion is Correct:** Glucose molecules are too large and polar to pass through the lipid bilayer by simple diffusion. Instead, they require specific carrier proteins known as **GLUT (Glucose Transporters)**, primarily **GLUT-1**. This process moves glucose down a concentration gradient (from maternal blood to fetal blood) without the expenditure of energy (ATP). This ensures a rapid and continuous supply of glucose to meet fetal metabolic demands. **2. Why Other Options are Incorrect:** * **Endocytosis:** This involves the engulfing of large molecules (e.g., IgG antibodies) into vesicles. It is not used for small metabolic substrates like glucose. * **Active Transport:** This requires ATP to move substances against a concentration gradient. Examples include **Amino acids**, calcium, and water-soluble vitamins. * **Simple Diffusion:** This is reserved for small, uncharged molecules or gases moving down a gradient without a carrier. Examples include **Oxygen ($O_2$)**, Carbon dioxide ($CO_2$), water, and most drugs. **Clinical Pearls for NEET-PG:** * **GLUT-1** is the predominant glucose transporter in the human placenta. * **Fetal glucose levels** are typically 20–30 mg/dL lower than maternal levels to maintain the concentration gradient. * **Insulin** does NOT cross the placenta; the fetus produces its own insulin in response to maternal glucose levels. * **Mnemonic for Placental Transport:** * **S**imple Diffusion: **G**ases (**S**moking/**G**as) * **F**acilitated Diffusion: **G**lucose (**F**ast **G**lucose) * **A**ctive Transport: **A**mino Acids (**A**ctive/**A**mino) * **P**inocytosis/Endocytosis: **I**gG (**P**rotective **I**gG)

Question 1

As menstruation ends, estrogen levels in the blood rise rapidly. What is the source of the estrogen?

Accepted Answer

Developing follicles

Answer

Corpus luteum

Answer

Endometrium

Answer

Stromal cells of the ovaries

Question 2

Corpus luteum formation occurs on which day of the menstrual cycle?

Accepted Answer

15th day

Answer

22nd day

Answer

1st day

Answer

28th day

Question 3

Which of the following changes occurs during pregnancy?

Accepted Answer

Fibrinogen level increases

Answer

Plasmin level decreases

Answer

Fibrinolytic activity decreases

Answer

Hemodilution does not occur

Question 4

Levels of which of the following hormones are increased in post-menopausal women?

Accepted Answer

FSH

Answer

Estrogen

Answer

Progesterone

Answer

Cortisol

Question 5

Which hormone shows no significant change in its levels throughout the menstrual cycle?

Accepted Answer

Activin

Answer

Inhibin

Answer

FSH

Answer

GnRH

Question 6

Which hormone is involved in the milk secretion reflex?

Accepted Answer

Prolactin

Answer

Oxytocin

Answer

Vasopressin

Answer

Progesterone

Question 7

Which one of the following androgens is not produced by Leydig cells of the testis?

Accepted Answer

Dihydrotestosterone

Answer

Testosterone

Answer

Androstenedione

Answer

Dehydroepiandrosterone

Question 8

The ovulatory period corresponds to:

Accepted Answer

14 days before menstruation

Answer

The day of menstruation

Answer

Increase in basal body temperature

Answer

14 days after menstruation

Question 9

In a study it is observed that the right ovary ovulates more frequently than the left. What is the most likely exception among the following explanations for this phenomenon?

Accepted Answer

Right-handedness is more common in the population

Answer

Anatomical asymmetry

Answer

Difference in blood supply to both ovaries

Answer

Some embryological basis

Question 10

Glucose is transported from the placenta to the fetus by which mechanism?

Accepted Answer

Facilitated diffusion

Answer

Endocytosis

Answer

Active transport

Answer

Simple diffusion

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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