Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 331: What hormone causes the increase in body temperature during ovulation?

A. Estrogen
B. Progesterone (Correct Answer)
C. LH
D. FSH

Explanation: **Explanation:** The correct answer is **Progesterone**. **Mechanism:** The increase in basal body temperature (BBT) during the menstrual cycle is a classic physiological effect of progesterone. After ovulation occurs, the ruptured follicle transforms into the **corpus luteum**, which begins secreting high levels of progesterone. Progesterone acts directly on the **hypothalamus** (the body’s thermostat), shifting the set-point upward. This results in a thermogenic effect, causing a rise in BBT by approximately **0.3°C to 0.5°C (0.5°F to 1.0°F)** during the luteal phase. This elevation persists until menstruation, when progesterone levels drop. **Analysis of Incorrect Options:** * **A. Estrogen:** Estrogen actually has a mild "cooling" effect and tends to lower body temperature slightly during the pre-ovulatory (follicular) phase. * **C. LH (Luteinizing Hormone):** While the LH surge triggers the process of ovulation itself, the hormone does not have direct thermogenic properties. * **D. FSH (Follicle Stimulating Hormone):** FSH is responsible for follicular recruitment and growth; it has no significant impact on systemic body temperature. **High-Yield Clinical Pearls for NEET-PG:** * **Biphasic Chart:** A normal ovulatory cycle shows a biphasic temperature pattern (lower in the follicular phase, higher in the luteal phase). A monophasic chart suggests anovulation. * **Timing:** The temperature rise occurs *after* ovulation has already happened. Therefore, BBT monitoring is better for confirming ovulation rather than predicting it. * **Progesterone’s other effects:** It is also responsible for the "secretory" changes in the endometrium and the thickening of cervical mucus (making it hostile to sperm).

Question 332: In postmenopausal women, estrogen is metabolized mostly into which of the following?

A. Estriol
B. Estrone (Correct Answer)
C. Estradiol
D. Androstenedione

Explanation: **Explanation:** In postmenopausal women, the primary source of estrogen shifts from the ovaries to peripheral tissues. The correct answer is **Estrone (E1)** because, after menopause, ovarian follicular activity ceases, leading to a drastic decline in Estradiol (E2) levels. Instead, androgens (primarily androstenedione) secreted by the adrenal cortex and ovarian stroma are converted into **Estrone** via the enzyme **aromatase** in peripheral adipose tissue. **Analysis of Options:** * **Estrone (E1):** The dominant estrogen in **postmenopausal** women. It is less potent than estradiol and is formed via peripheral aromatization. * **Estradiol (E2):** The most potent and dominant estrogen during the **reproductive years** (pre-menopausal). It is primarily produced by the granulosa cells of the developing follicles. * **Estriol (E3):** The least potent estrogen and the dominant form during **pregnancy**, produced primarily by the feto-placental unit. * **Androstenedione:** This is an **androgen precursor**, not an estrogen. While it is the substrate for estrone production in postmenopausal women, it is not the metabolite of estrogen itself. **High-Yield Clinical Pearls for NEET-PG:** * **Potency Order:** Estradiol (E2) > Estrone (E1) > Estriol (E3). * **Source of E1:** In obese postmenopausal women, increased adipose tissue leads to higher peripheral aromatization, resulting in elevated estrone levels, which is a significant risk factor for **endometrial carcinoma**. * **LH/FSH Ratio:** In menopause, both LH and FSH rise due to loss of negative feedback, but **FSH increases more significantly** (FSH > LH) because of the loss of Inhibin.

Question 333: Which of the following statements about estrogen action is FALSE?

A. Stimulates secondary sex characteristics in females.
B. Stimulates osteoclasts. (Correct Answer)
C. Decreases LDL cholesterol.
D. Increases blood coagulability.

Explanation: ### Explanation The correct answer is **B. Stimulates osteoclasts.** **1. Why Option B is False (The Correct Answer):** Estrogen is fundamentally **bone-protective**. It does not stimulate osteoclasts; rather, it **inhibits osteoclast activity** and promotes their apoptosis. The primary mechanism involves the RANK/RANKL pathway: estrogen increases the production of **Osteoprotegerin (OPG)**, a decoy receptor that binds to RANKL, preventing it from activating the RANK receptor on osteoclasts. This inhibits bone resorption. This is why post-menopausal women (who have low estrogen) are at a high risk for osteoporosis. **2. Analysis of Other Options:** * **A. Stimulates secondary sex characteristics:** This is a primary function of estrogen. It promotes breast development (ductal growth), female fat distribution (hips/thighs), and the maturation of the vagina and uterus. * **C. Decreases LDL cholesterol:** Estrogen has a cardioprotective effect. It increases HDL ("good" cholesterol) and decreases LDL ("bad" cholesterol) by increasing the expression of LDL receptors in the liver, enhancing LDL clearance. * **D. Increases blood coagulability:** Estrogen is **pro-thrombotic**. It increases the hepatic synthesis of clotting factors (II, VII, IX, X, and fibrinogen) and decreases anticoagulants like Protein S and Antithrombin III. This explains the increased risk of DVT/stroke in women taking Oral Contraceptive Pills (OCPs). **3. NEET-PG High-Yield Pearls:** * **Bone Effect:** Estrogen causes the **closure of epiphyseal plates** in both males and females, ending linear growth. * **Cervical Mucus:** Under estrogen influence, cervical mucus becomes thin, watery, and alkaline, showing a characteristic **"Fern pattern"** on microscopy. * **Temperature:** Unlike progesterone (which is thermogenic), estrogen does not increase basal body temperature.

Question 334: What type of estrogen is found in the highest concentration in adult females?

A. Estrone
B. Estriol
C. Estradiol (Correct Answer)
D. None

Explanation: **Explanation:** In adult females of reproductive age, **Estradiol (E2)** is the most potent and abundant form of estrogen. It is primarily synthesized in the ovaries by the granulosa cells through the aromatization of androgens. Its concentration fluctuates during the menstrual cycle, peaking just before ovulation. **Analysis of Options:** * **Estradiol (E2):** The "estrogen of the reproductive years." It is the most biologically active form and is responsible for the development of secondary sexual characteristics and the regulation of the menstrual cycle. * **Estrone (E1):** The "estrogen of menopause." It is a weaker estrogen produced mainly in adipose tissue via peripheral conversion. It is the predominant circulating estrogen after menopause. * **Estriol (E3):** The "estrogen of pregnancy." It is the least potent form and is produced in large quantities by the placenta. High levels of E3 serve as an indicator of fetal well-being. **NEET-PG High-Yield Pearls:** 1. **Potency Order:** Estradiol (E2) > Estrone (E1) > Estriol (E3). 2. **Source:** Estradiol is produced by the **Aromatase** enzyme (induced by FSH) in the ovary. 3. **Clinical Correlation:** In Polycystic Ovary Syndrome (PCOS), there is an increased E1:E2 ratio due to the peripheral conversion of androstenedione to estrone in adipose tissue. 4. **Mnemonic:** Remember the numbers: **E1** (One/m**O**ne-opause), **E2** (Two/Ovaries-**T**wo), **E3** (Three/Placenta-**T**hree).

Question 335: The placenta secretes a hormone that is utilized in the early detection of pregnancy. This hormone is:

A. Endothelial growth factor (EGF)
B. Human chorionic gonadotropin (hCG) (Correct Answer)
C. Human chorionic somatotropin (HCS)
D. Relaxin

Explanation: ### Explanation **Correct Option: B. Human chorionic gonadotropin (hCG)** **Why it is correct:** Human chorionic gonadotropin (hCG) is a glycoprotein hormone secreted by the **syncytiotrophoblast** of the placenta. Its primary physiological role is to maintain the **corpus luteum** during the first trimester, ensuring the continued secretion of progesterone until the placenta takes over steroidogenesis (the luteal-placental shift). Because hCG is produced exclusively by trophoblastic tissue and appears in maternal blood and urine as early as **8–9 days after ovulation** (shortly after implantation), it serves as the definitive biological marker for the early detection of pregnancy. **Why the other options are incorrect:** * **A. Endothelial growth factor (EGF):** While involved in placental development and trophoblast proliferation, it is a growth factor, not a diagnostic hormone for pregnancy detection. * **C. Human chorionic somatotropin (hCS):** Also known as Human Placental Lactogen (hPL). It is involved in maternal metabolism (anti-insulin effect) to ensure glucose supply to the fetus. It rises later in pregnancy and is not used for early diagnosis. * **D. Relaxin:** Secreted initially by the corpus luteum and later by the placenta to soften the cervix and pelvic ligaments. It is not specific enough for early pregnancy testing. **High-Yield Clinical Pearls for NEET-PG:** * **Structure:** hCG is a dimer; the **$\alpha$-subunit** is identical to LH, FSH, and TSH. The **$\beta$-subunit** is unique, which is why pregnancy tests specifically measure **$\beta$-hCG**. * **Doubling Time:** In early normal pregnancy, $\beta$-hCG levels double approximately every **48 hours**. * **Peak Levels:** hCG levels reach their peak at **8–10 weeks** of gestation and then decline to a lower plateau. * **Tumor Marker:** Pathologically high levels are seen in **Hydatidiform mole** and **Choriocarcinoma**. Low levels for gestational age may suggest an ectopic pregnancy or impending abortion.

Question 336: Which of the following hormonal activities is expected immediately prior to ovulation?

A. LH surge (Correct Answer)
B. FSH surge
C. Progesterone surge
D. Estrogen surge

Explanation: **Explanation:** The correct answer is **LH surge**. Ovulation is primarily triggered by a dramatic rise in Luteinizing Hormone (LH), which occurs approximately 24–36 hours before the release of the oocyte. **Why LH surge is correct:** During the late follicular phase, rising levels of Estrogen (secreted by the dominant follicle) reach a critical threshold (typically >200 pg/mL for ~48 hours). This switches Estrogen’s feedback from negative to **positive feedback** on the anterior pituitary and hypothalamus. This results in a massive release of LH. The LH surge is essential as it resumes meiosis I in the oocyte and triggers the inflammatory cascade required for follicular rupture. **Analysis of Incorrect Options:** * **FSH surge:** While an FSH peak occurs simultaneously with the LH surge (due to GnRH stimulation), it is less pronounced and not the primary driver of ovulation. * **Progesterone surge:** Progesterone levels only begin to rise *after* ovulation, secreted by the newly formed Corpus Luteum. A very minor pre-ovulatory rise occurs, but it is not a "surge." * **Estrogen surge:** Estrogen levels peak **before** the LH surge. While the Estrogen peak is the *cause* of the LH surge, the LH surge is the event that occurs *immediately* prior to ovulation. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** Ovulation occurs **10–12 hours after the LH peak** and **24–36 hours after the start of the LH surge**. * **Best Predictor:** The LH surge is the most reliable hormonal marker used in ovulation predictor kits (OPKs). * **Meiosis:** The LH surge triggers the completion of **Meiosis I** (arrested in prophase) and the start of **Meiosis II** (arrested in metaphase). * **Mittelschmerz:** Mid-cycle pelvic pain associated with ovulation.

Question 337: Which among the following hormones, in a lactating mother, is responsible for the maintenance and proliferation of milk-secreting breast tissue?

A. Estrogen
B. Oxytocin
C. Prolactin (Correct Answer)
D. Progesterone

Explanation: ***Prolactin***- **Prolactin** is the key hormone responsible for establishing and maintaining **lactation** (milk production), and it drives the final proliferation and differentiation of the **alveolar epithelial cells** during the later stages of pregnancy and postpartum state.- While other hormones contribute to overall breast development, Prolactin ensures the functional readiness and continued growth/maintenance of the glandular tissue necessary for milk synthesis.*Oxytocin*- **Oxytocin** is responsible for the **milk ejection reflex** (let-down), causing the contraction of **myoepithelial cells** around the alveoli.- It does not promote the proliferative growth or differentiation of the secretory breast tissue itself.*Estrogen*- **Estrogen** is primarily responsible for the growth and development of the **ductal system** of the breast during puberty and pregnancy.- High levels of estrogen during pregnancy actively **inhibit** the full secretory function of prolactin until after delivery.*Progesterone*- **Progesterone** is crucial for the development of the **lobular-alveolar system** during pregnancy.- Its rapid decline after delivery is essential to remove the inhibitory block, allowing **prolactin** to fully initiate and manage milk secretion in the lactating phase.

Question 338: Hormone responsible for milk ejection reflex in the image shown?

A. GH
B. TSH
C. Oxytocin (Correct Answer)
D. FSH

Explanation: ***Oxytocin*** - The image shows a baby breastfeeding, which involves the **suckling reflex**. This reflex triggers the release of oxytocin from the posterior pituitary gland. - Oxytocin is crucial for the **milk ejection reflex** (or let-down reflex), as it causes the contraction of myoepithelial cells surrounding the alveoli in the mammary glands, expelling milk. *TSH* - Thyroid-Stimulating Hormone (TSH) is released from the anterior pituitary and its primary role is to stimulate the **thyroid gland** to produce thyroid hormones. - It is involved in regulating the body's **metabolism** and is not directly responsible for lactation. *GH* - Growth Hormone (GH) is secreted by the anterior pituitary and is essential for overall **somatic growth**, particularly of bones and muscles. - While it contributes to mammary gland development, it does not mediate the immediate process of milk ejection during breastfeeding. *FSH* - Follicle-Stimulating Hormone (FSH) is an anterior pituitary hormone that plays a key role in the reproductive cycle. - It stimulates the growth of **ovarian follicles** in females and **spermatogenesis** in males, and is not involved in lactation.

Question 339: During spermatogenesis, which of the following hormones inhibits Follicle-Stimulating Hormone (FSH) secretion?

A. Luteinizing Hormone (LH)
B. Testosterone
C. Inhibin (Correct Answer)
D. Estrogen

Explanation: ***Inhibin*** - **Inhibin** is produced by **Sertoli cells** in the seminiferous tubules, acting as a crucial regulator of spermatogenesis. - It specifically targets the anterior pituitary gland to implement a **negative feedback loop**, reducing the secretion of **FSH** (Follicle-Stimulating Hormone) when sperm production levels are adequate. *Testosterone* - **Testosterone** is the primary androgen required for the maintenance and stimulation of spermatogenesis within the seminiferous tubules. - High systemic levels of testosterone primarily inhibit the secretion of **GnRH** (from the hypothalamus) and **LH** (from the pituitary), rather than specifically inhibiting FSH production. *Luteinizing Hormone (LH)* - **LH** acts on the **Leydig cells** in the testes, stimulating them to produce testosterone. - It does not directly inhibit FSH; rather, it is part of the **Hypothalamic-Pituitary-Gonadal (HPG) axis** regulation system. *Estrogen* - While small amounts of **estrogen** are produced in males (via aromatization of testosterone), it does not play a primary role in the negative feedback inhibition of FSH during spermatogenesis. - In males, **inhibin** is the specific hormone that directly targets FSH secretion from the anterior pituitary.

Question 340: What is the cause of LH (Luteinizing Hormone) surge?

A. LH
B. Progesterone
C. FSH
D. Estradiol (Correct Answer)

Explanation: ***Estradiol*** - The cause of LH surge- During the late follicular phase, the dominant follicle secretes increasingly high levels of **Estradiol** (a potent estrogen). When these levels remain high for a prolonged period (typically 48–50 hours) above a critical threshold, it switches from exerting negative feedback to **positive feedback** on the hypothalamus and anterior pituitary. - This positive feedback stimulates a massive release of **GnRH** and, subsequently, a sudden, sharp, increase in **LH** secretion, known as the LH surge, which prepares the dominant follicle for ovulation. *FSH* - FSH is essential for initiating the **follicular development** (growth and maturation of ovarian follicles) preceding the surge, but it is not the direct trigger for the LH surge. - Although FSH levels also rise slightly during the surge (known as the **FSH surge**), this rise is secondary to the primary positive feedback mechanism driven by Estradiol. *Progesterone* - Progesterone levels are typically low during the late follicular phase when the LH surge occurs; its primary rise happens **after ovulation** during the luteal phase. - While Progesterone contributes to the total feedback loop around the surge, it cannot initiate the surge itself, and its main role is preparing the **endometrium** and supporting a potential pregnancy. *LH* - LH (*Luteinizing hormone*) is the hormone whose concentration surges; it is the **effect** of the positive feedback loop, not the underlying cause. - The rise in LH concentration is a direct response of the **anterior pituitary** to the high levels of Estradiol acting upon it.

Practice by Chapter

Male Reproductive Physiology

Practice Questions

Spermatogenesis and Sperm Function

Practice Questions

Female Reproductive Physiology

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Menstrual Cycle

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Ovulation and Fertilization

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Physiology of Pregnancy

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Parturition

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Lactation

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Sexual Differentiation and Development

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Reproductive Aging

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