Reproductive Physiology Practice Questions

Q: Testosterone in males is secreted from which of the following cells?

Leydig cells. **Explanation:** **Correct Answer: A. Leydig cells** The primary source of testosterone in males is the **Leydig cells** (also known as interstitial cells), located in the connective tissue between the seminiferous tubules. This process is regulated by **Luteinizing Hormone (LH)** from the anterior pituitary, which binds to G-protein coupled receptors on Leydig cells to stimulate the conversion of cholesterol to testosterone. **Analysis of Incorrect Options:** * **B. Sertoli cells:** These are "nurturing" cells located within the seminiferous tubules. Their primary functions include supporting spermatogenesis, forming the blood-testis barrier, and secreting **Inhibin B** and **Androgen Binding Protein (ABP)** under the influence of FSH. They do not synthesize testosterone. * **C. Seminal vesicles:** These are accessory glands that contribute about 60-70% of the seminal fluid volume. They secrete fructose (energy for sperm), prostaglandins, and clotting proteins, but not hormones. * **D. Epididymis:** This is the site for sperm maturation and storage. While it is an androgen-dependent organ, it does not produce testosterone. **High-Yield Clinical Pearls for NEET-PG:** * **LH acts on Leydig cells** (Mnemonic: **L**H = **L**eydig). * **FSH acts on Sertoli cells** (Mnemonic: **F**SH = **S**ertoli). * **Intratesticular testosterone** levels are 20–100 times higher than serum levels, which is essential for normal spermatogenesis. This high concentration is maintained by **ABP** (secreted by Sertoli cells). * The rate-limiting step in testosterone synthesis is the conversion of cholesterol to pregnenolone by the enzyme **cytochrome P450scc** (cholesterol side-chain cleavage enzyme).

Q: In the physiology of the menstrual cycle, all of the following statements are true EXCEPT?

The follicular phase is constant in length.. **Explanation:** The menstrual cycle is divided into the follicular (proliferative) and luteal (secretory) phases. Understanding the variability of these phases is a high-yield concept for NEET-PG. **1. Why Option B is the Correct Answer (The False Statement):** The **luteal phase is constant** in length, typically lasting 14 days (range 13–15 days) due to the fixed lifespan of the corpus luteum. In contrast, the **follicular phase is highly variable**. Variations in total cycle length (e.g., a 28-day vs. 35-day cycle) are almost entirely due to differences in the duration of the follicular phase. **2. Analysis of Other Options:** * **Option A:** Ovulation is triggered by the LH surge. It occurs approximately **32–36 hours after the onset** of the surge and 10–12 hours after the LH peak. * **Option C:** Menstruation is a "withdrawal bleed." When fertilization fails, the corpus luteum involutes, leading to a sharp drop in progesterone. This causes spiral artery vasospasm, tissue ischemia, and endometrial shedding. * **Option D:** A normal menstrual cycle ranges from **21 to 35 days** (average 28 days). Cycles outside this range are classified as polymenorrhea ( 35 days). **Clinical Pearls for NEET-PG:** * **LH Surge Trigger:** Caused by a positive feedback effect of Estrogen (levels >200 pg/mL for >48 hours). * **Mittelschmerz:** Mid-cycle pelvic pain associated with ovulation. * **Progesterone:** The "hormone of pregnancy," responsible for the secretory changes in the endometrium and the rise in basal body temperature (0.5°F) post-ovulation.

Q: Which of the following is NOT associated with progesterone?

Proliferative phase of the menstrual cycle. **Explanation:** The correct answer is **B. Proliferative phase of the menstrual cycle.** The menstrual cycle is divided into two main phases: the **proliferative (follicular) phase** and the **secretory (luteal) phase**. The proliferative phase is dominated by **Estrogen**, which is secreted by the developing ovarian follicles to stimulate endometrial growth. Progesterone levels remain baseline during this phase. **Analysis of Options:** * **A. Ovulation:** While LH triggers ovulation, the process is preceded by a small pre-ovulatory rise in progesterone. Furthermore, the presence of progesterone is the definitive marker that ovulation has occurred, as it is secreted by the resulting Corpus Luteum. * **C. Thermogenesis:** Progesterone has a direct effect on the hypothalamus, increasing the basal body temperature (BBT) by approximately 0.5°F (0.3°C) after ovulation. This is a classic clinical marker used to track the luteal phase. * **D. Secretory phase:** This phase is entirely dependent on Progesterone. It transforms the estrogen-primed endometrium into a secretory state, making it receptive for implantation by increasing vascularity and glycogen storage. **High-Yield NEET-PG Pearls:** * **Source:** Progesterone is primarily secreted by the **Corpus Luteum** (stimulated by LH) and later by the **Placenta** (after 8–10 weeks). * **Pregnancy:** It is the "hormone of pregnancy" because it maintains endometrial integrity and decreases uterine contractility (quiescence). * **Diagnostic Test:** A serum progesterone level >3 ng/mL on Day 21 of the cycle is the gold standard for confirming that ovulation has occurred.

Q: Which one of the following substances is the most potent androgen?

Dihydrotestosterone. **Explanation:** The potency of an androgen is determined by its affinity for the androgen receptor (AR) and its ability to initiate gene transcription. **Why Dihydrotestosterone (DHT) is the correct answer:** DHT is the most potent naturally occurring androgen [1]. It is synthesized from testosterone by the enzyme **5Ͱ-reductase** in peripheral tissues (like the prostate and skin). DHT has a **2-3 times higher affinity** for the androgen receptor than testosterone and dissociates from the receptor much more slowly. This makes its biological effect significantly more powerful, especially in the development of male external genitalia and prostate growth [3]. **Analysis of Incorrect Options:** * **Testosterone (Option D):** While it is the primary circulating androgen produced by Leydig cells [2], it acts as a "pro-hormone" for DHT in many tissues. It is less potent than DHT but more potent than the adrenal androgens. * **Androstenedione (Option C):** This is a weak androgen produced by the adrenal cortex and testes [1]. It serves primarily as a precursor for the synthesis of testosterone and estrogens. * **Dehydroepiandrosterone (DHEA) (Option A):** (Note: The option lists "Dihydroepiandrostendione," likely referring to DHEA). DHEA is a very weak adrenal androgen with low affinity for the androgen receptor. It must be converted to testosterone or DHT to exert significant androgenic effects. **NEET-PG High-Yield Pearls:** * **Potency Order:** DHT > Testosterone > Androstenedione > DHEA. * **Enzyme Fact:** 5Ͱ-reductase inhibitors (e.g., **Finasteride**) are used clinically to treat BPH and male pattern baldness by blocking the conversion of testosterone to the more potent DHT. * **Clinical Correlation:** In **5Ͱ-reductase deficiency**, individuals have normal internal male structures (testosterone-dependent) but ambiguous or female-looking external genitalia at birth (DHT-dependent) [3].

Q: In men, luteinizing hormone (LH) primarily controls the secretion of which hormone?

Testosterone. ### Explanation The hypothalamic-pituitary-gonadal (HPG) axis regulates male reproductive function through two primary gonadotropins: **Luteinizing Hormone (LH)** and **Follicle-Stimulating Hormone (FSH)**. **Why Testosterone is Correct:** LH acts specifically on the **Leydig cells** (interstitial cells) located in the connective tissue between seminiferous tubules. LH binds to G-protein coupled receptors on these cells, stimulating the conversion of cholesterol to pregnenolone via the enzyme *cholesterol desmolase*. This is the rate-limiting step in the synthesis of **Testosterone**. Therefore, LH is the primary trophic hormone for testosterone production. **Why Other Options are Incorrect:** * **Inhibin:** This is secreted by **Sertoli cells** in response to **FSH** and high sperm counts. It provides negative feedback specifically to the anterior pituitary to inhibit FSH secretion. * **Anti-Müllerian Hormone (AMH):** Produced by fetal Sertoli cells to cause regression of Müllerian ducts. In adults, it is a marker of Sertoli cell function but is not primarily regulated by LH. * **Androgen-binding protein (ABP):** This is synthesized by **Sertoli cells** under the influence of **FSH**. ABP helps maintain high local concentrations of testosterone within the seminiferous tubules, which is essential for spermiogenesis. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **L**H acts on **L**eydig cells; **S**ertoli cells are stimulated by **F**SH (to support **S**permatogenesis). * **Negative Feedback:** Testosterone inhibits both the Hypothalamus (GnRH) and the Anterior Pituitary (LH), whereas Inhibin only inhibits the Anterior Pituitary (FSH). * **Blood-Testis Barrier:** Formed by tight junctions between Sertoli cells, protecting developing germ cells from the immune system.

Q: Which hormones stimulate spermatogenesis?

Testosterone and Follicle-stimulating hormone. **Explanation:** Spermatogenesis is the complex process of sperm cell development occurring within the seminiferous tubules of the testes. This process is primarily regulated by the **Hypothalamic-Pituitary-Gonadal (HPG) axis**. **Why Option D is Correct:** * **Follicle-stimulating hormone (FSH):** Secreted by the anterior pituitary, FSH binds to receptors on **Sertoli cells**. It stimulates the production of Androgen Binding Protein (ABP) and initiates the process of spermatogenesis. * **Testosterone:** Luteinizing Hormone (LH) stimulates **Leydig cells** to produce testosterone. High local concentrations of testosterone (maintained by ABP) are essential for the maturation of spermatids into spermatozoa (spermiogenesis) and the maintenance of the germ cell population. **Why Other Options are Incorrect:** * **Option A:** Thyroxine (T4) regulates basal metabolic rate, and Parathormone (PTH) regulates calcium homeostasis. While thyroid disorders can indirectly affect fertility, they are not the primary drivers of spermatogenesis. * **Option B:** Insulin and Glucagon are pancreatic hormones responsible for glucose metabolism. * **Option C:** ADH (Vasopressin) regulates water retention in the kidneys, and Oxytocin is involved in milk ejection and uterine contractions. **High-Yield NEET-PG Pearls:** * **Sertoli Cells:** Often called "Nurse Cells"; they form the blood-testis barrier and provide nutrition to developing sperm. * **Inhibin B:** Secreted by Sertoli cells, it provides negative feedback specifically to FSH. * **LH vs. FSH:** Remember the mnemonic: **L**H acts on **L**eydig cells; **S**ertoli cells are stimulated by F**S**H. * **Duration:** The entire process of spermatogenesis takes approximately **74 days**.

Q: A couple's semen analysis report shows oligospermia. Which of the following medications can be given to increase sperm count?

FSH. **Explanation:** The correct answer is **FSH (Follicle-Stimulating Hormone)**. **1. Why FSH is correct:** Spermatogenesis is primarily regulated by the Hypothalamic-Pituitary-Gonadal axis. FSH plays a critical role by binding to receptors on **Sertoli cells** within the seminiferous tubules. This stimulation induces the production of Androgen Binding Protein (ABP), which maintains high local concentrations of testosterone necessary for sperm production. In clinical practice, exogenous FSH (or hMG) is used to treat hypogonadotropic hypogonadism to directly stimulate the germinal epithelium and increase sperm count in oligospermic men. **2. Why the other options are incorrect:** * **LH (Luteinizing Hormone):** While LH stimulates **Leydig cells** to produce testosterone, it does not directly stimulate the seminiferous tubules. While testosterone is essential for spermatogenesis, LH alone is usually insufficient to restore a normal sperm count in the absence of FSH. * **Estrogen:** High levels of estrogen exert negative feedback on the hypothalamus and pituitary, inhibiting the release of GnRH, FSH, and LH. This would suppress, rather than increase, sperm production. * **Progesterone:** Similar to estrogen, progesterone can inhibit the gonadotropin axis and is not used to treat male infertility. **Clinical Pearls for NEET-PG:** * **Sertoli Cells:** "Nursing cells" stimulated by **FSH** (FSH = Follicle/Sperm stimulating). * **Leydig Cells:** Stimulated by **LH** to produce testosterone (L = Leydig/Luteinizing). * **Oligospermia Definition:** Sperm count **<15 million/ml** (WHO 2010/2021 criteria). * **Clomiphene Citrate:** Often used off-label in male infertility to increase endogenous FSH/LH by blocking estrogen feedback.

Question 1

Testosterone in males is secreted from which of the following cells?

Accepted Answer

Leydig cells

Answer

Sertoli cells

Answer

Seminal vesicles

Answer

Epididymis

Question 2

Which of the following could inhibit the initiation of labor?

Accepted Answer

Administration of an antagonist of PGE2 effects

Answer

Administration of an antagonist of the actions of progesterone

Answer

Administration of LH

Answer

Mechanically dilating and stimulating the cervix

Question 3

Which clotting factor decreases during pregnancy?

Accepted Answer

Fibrinogen

Answer

Factor XIII

Answer

Factor VIII

Answer

Factor X

Question 4

In the physiology of the menstrual cycle, all of the following statements are true EXCEPT?

Accepted Answer

The follicular phase is constant in length.

Answer

Ovulation follows 36 hours after the onset of the LH surge.

Answer

Withdrawal of endogenous progesterone results in endometrial breakdown and subsequent menstruation.

Answer

The average cycle length is 21-35 days.

Question 5

Which of the following is NOT associated with progesterone?

Accepted Answer

Proliferative phase of the menstrual cycle

Answer

Ovulation

Answer

Thermogenesis

Answer

Secretory phase of the menstrual cycle

Question 6

Which one of the following substances is the most potent androgen?

Accepted Answer

Dihydrotestosterone

Answer

Dihydroepiandrostendione

Answer

Androstendione

Answer

Testosterone

Question 7

Which of the following statements accurately describes the hormonal changes during a normal menstrual cycle?

Accepted Answer

Progesterone levels are highest during the secretory phase.

Answer

LH levels are lowest in the mid-cycle.

Answer

FSH levels are highest during the luteal phase.

Answer

Estradiol levels are highest during the mid-cycle.

Question 8

In men, luteinizing hormone (LH) primarily controls the secretion of which hormone?

Accepted Answer

Testosterone

Answer

Inhibin

Answer

Anti-Müllerian hormone (AMH)

Answer

Androgen-binding protein (ABP)

Question 9

Which hormones stimulate spermatogenesis?

Accepted Answer

Testosterone and Follicle-stimulating hormone

Answer

Thyroxine and parathormone

Answer

Insulin and glucagon

Answer

Antidiuretic hormone and Oxytocin

Question 10

A couple's semen analysis report shows oligospermia. Which of the following medications can be given to increase sperm count?

Accepted Answer

FSH

Answer

LH

Answer

Estrogen

Answer

Progesterone

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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