Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 461: During early pregnancy (first trimester), estrogen is primarily secreted by which of the following structures?

A. Hypothalamus
B. Fetal ovary
C. Pituitary
D. Maternal ovary (Correct Answer)

Explanation: ***Maternal ovary*** - During **early pregnancy** (first 8-10 weeks), the **corpus luteum** in the maternal ovary is the primary source of **estrogen** and **progesterone**, essential for maintaining the pregnancy until the placenta matures. - The corpus luteum is maintained by **hCG** (human chorionic gonadotropin) secreted by the developing placenta. - After the first trimester, the placenta takes over as the main source of estrogen production. *Fetal ovary* - The **fetal ovary** does not contribute to estrogen production during pregnancy. - The fetal ovary remains undeveloped during gestation and only becomes active after birth during puberty. *Pituitary* - The **pituitary gland** produces **gonadotropins** (LH and FSH) which regulate hormone production, but does not directly secrete estrogen. - During pregnancy, pituitary gonadotropin secretion is actually suppressed due to high levels of placental hormones. *Hypothalamus* - The **hypothalamus** secretes **GnRH** (gonadotropin-releasing hormone) to regulate the pituitary, but does not produce estrogen. - Its role is in the hormonal control cascade, not in direct steroid hormone synthesis.

Question 462: Ovulation is associated with a sudden rise in the level of which of the following hormones?

A. Prolactin
B. Testosterone
C. LH (Correct Answer)
D. Oxytocin

Explanation: ***LH*** - A rapid surge in **luteinizing hormone (LH)**, known as the **LH surge**, is the direct trigger for ovulation. - This **LH surge** stimulates the final maturation of the dominant follicle and its rupture, releasing the ovum. *Prolactin* - **Prolactin** is primarily involved in **milk production** and has no direct role in triggering ovulation. - High levels of **prolactin** can actually inhibit ovulation by suppressing gonadotropin-releasing hormone (GnRH). *Testosterone* - **Testosterone** is an androgen predominantly found in males, and while present in females, it is not responsible for triggering ovulation. - Its primary roles in females include contributing to **libido** and **bone density**. *Oxytocin* - **Oxytocin** plays a crucial role in uterine contractions during labor and milk ejection during breastfeeding. - It does not have a direct role in initiating the process of ovulation.

Question 463: Adequate steroidogenesis in the corpus luteum depends on serum levels of

A. GnRH
B. FSH
C. LH (Correct Answer)
D. Oestrogen

Explanation: ***Correct: LH*** - **Luteinizing Hormone (LH)** is crucial for the **formation and maintenance of the corpus luteum** after ovulation. - LH directly stimulates the corpus luteum to produce **progesterone** and some **estrogen**, a process known as **steroidogenesis**. - LH binds to receptors on luteal cells and is the **primary hormonal driver** of corpus luteum function. *Incorrect: GnRH* - **Gonadotropin-releasing hormone (GnRH)** is released from the hypothalamus and stimulates the anterior pituitary to release FSH and LH. - While essential for the overall reproductive axis, **GnRH does not directly act on the corpus luteum** for steroidogenesis. *Incorrect: FSH* - **Follicle-stimulating hormone (FSH)** is primarily responsible for the growth and development of ovarian follicles during the follicular phase. - While FSH has some synergistic effects, its **direct role in corpus luteum steroidogenesis is minimal** compared to LH. *Incorrect: Oestrogen* - **Estrogen** is a steroid hormone produced by the ovaries, and later by the corpus luteum and placenta. - Estrogen is a **product of steroidogenesis, not its primary driver** in the corpus luteum.

Question 464: Which of the following C-21 steroid hormones is primarily associated with reproductive health?

A. Corticosterone
B. Cortisol
C. Aldosterone
D. Progesterone (Correct Answer)

Explanation: ***Progesterone*** - **Progesterone** is a C-21 steroid hormone primarily involved in the **menstrual cycle**, **pregnancy**, and **embryogenesis**, making it crucial for female reproductive health. - It prepares the **endometrium** for the implantation of a fertilized egg and helps maintain pregnancy by preventing uterine contractions. *Cortisol* - **Cortisol** is a **glucocorticoid** primarily involved in stress response, metabolism, and immune function. - While it has broad effects, its main role is not directly associated with reproductive health. *Aldosterone* - **Aldosterone** is a **mineralocorticoid** that regulates **blood pressure** and **electrolyte balance** by controlling sodium and potassium levels. - It plays no direct role in reproductive health. *Corticosterone* - **Corticosterone** is a **glucocorticoid** and a precursor to aldosterone, mainly involved in stress response in some animals, similar to cortisol. - It is not a primary hormone for human reproductive health.

Question 465: What is the most likely consequence of prolonged testosterone treatment on male fertility?

A. Decreased sperm motility
B. Azoospermia (Correct Answer)
C. Decreased spermatogenesis
D. Decreased gonadotropins

Explanation: ***Azoospermia*** - Prolonged exogenous testosterone administration suppresses the **hypothalamic-pituitary-gonadal (HPG) axis**, leading to decreased **gonadotropin-releasing hormone (GnRH)**, then reduced **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)**. - Reduced FSH is critical for **spermatogenesis** in the seminiferous tubules, causing a severe reduction or complete absence of sperm in the ejaculate, known as azoospermia. *Decreased spermatogenesis* - While testosterone treatment does lead to decreased spermatogenesis, azoospermia represents the most severe and complete form of this reduction, indicating a total absence of sperm. - Spermatogenesis refers to the general process of sperm production, whereas **azoospermia** specifically describes the clinical outcome of no sperm. *Decreased sperm motility* - Poor sperm motility (**asthenozoospermia**) can occur due to various factors, but prolonged exogenous testosterone primarily affects **sperm production** rather than sperm movement. - Although sperm quality might decline, the most pronounced effect is on the **number of sperm** produced, potentially leading to complete absence. *Decreased gonadotropins* - Decreased gonadotropins (LH and FSH) are an **intermediate step** in the cascade, not the most likely direct consequence on sperm. - The suppression of LH and FSH then leads to the more direct testicular effect of reduced sperm production, ultimately culminating in **azoospermia**.

Question 466: Higher pulse frequency of GnRH is characteristic of which phase of the menstrual cycle?

A. Luteal phase
B. Menstrual phase
C. Early follicular phase
D. Late follicular phase (Correct Answer)

Explanation: ***Late follicular phase*** - As estrogen levels rise rapidly in the late follicular phase, the **GnRH pulse frequency increases significantly**, leading to the **LH surge** which triggers ovulation. - This higher frequency is crucial for sensitizing the pituitary to GnRH, maximizing LH release. *Early follicular phase* - The early follicular phase is characterized by a **lower frequency of GnRH pulses**, which favors **FSH secretion** to stimulate follicular growth. - As follicles mature, the estrogen feedback gradually increases leading to changes in pulse frequency. *Luteal phase* - During the luteal phase, the presence of **progesterone** exerts a strong negative feedback on the hypothalamus, leading to a **decreased frequency of GnRH pulses**. - This lower frequency helps maintain **LH and FSH at basal levels**, preventing new follicular development. *Menstrual phase* - The menstrual phase represents the beginning of a new cycle, with **GnRH pulse frequency being relatively low**, similar to the early follicular phase, due to low steroid hormone levels. - This low frequency is essential for **FSH support** in recruiting new follicles.

Question 467: Which of the following statements regarding events related to oogenesis is false?

A. Meiosis-II is not a reduction division
B. LH surge occurs 24-48 hrs. prior to ovulation
C. First polar body is released prior to ovulation. (Correct Answer)
D. Primary oocyte is arrested at prophase - I at birth.

Explanation: ***First polar body is released prior to ovulation - FALSE*** - This statement is **false** because the first polar body is released **during ovulation**, not prior to it. - The LH surge triggers the completion of **meiosis I**, which results in the formation of the secondary oocyte and the first polar body. - This process occurs **at the time of ovulation** (within hours of ovulation), not significantly before it. - The secondary oocyte (arrested in metaphase II) is what is actually ovulated along with the first polar body already extruded. *LH surge occurs 24-48 hrs. prior to ovulation - TRUE* - The **LH surge** peaks approximately **24-36 hours before ovulation**. - This surge triggers the final maturation of the oocyte and completion of meiosis I. - The timing is crucial for the coordination of ovulation. *Meiosis-II is not a reduction division - TRUE* - This statement is **true** because meiosis II is an **equational division**. - It involves separation of sister chromatids (similar to mitosis), not reduction in chromosome number. - The reduction division occurs in **meiosis I** (diploid → haploid). - Meiosis II maintains the haploid number established in meiosis I. *Primary oocyte is arrested at prophase-I at birth - TRUE* - **Primary oocytes** are formed during fetal development and enter **prophase I of meiosis I**. - They remain arrested at the **diplotene stage of prophase I** from fetal life until puberty. - This arrest is maintained until the LH surge triggers resumption of meiosis in selected follicles during each menstrual cycle.

Question 468: What is the mechanism by which hyperprolactinemia causes amenorrhea?

A. Inhibition of adrenal steroidogenesis
B. It causes hypogonadotropic hypogonadism
C. Inhibition of GnRH pulse secretion (Correct Answer)
D. It leads to decreased ovarian function due to low FSH and LH levels

Explanation: ***Inhibition of GnRH pulse secretion*** - **Hyperprolactinemia** directly inhibits the pulsatile release of **gonadotropin-releasing hormone (GnRH)** from the hypothalamus. - This disruption of GnRH pulsatility subsequently impairs the release of **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)** from the pituitary, leading to **anovulation** and **amenorrhea**. *Inhibition of adrenal steroidogenesis* - High prolactin levels do not primarily inhibit **adrenal steroidogenesis**; instead, they interfere with the **hypothalamic-pituitary-gonadal (HPG)** axis. - Adrenal steroidogenesis largely involves the production of **androgens**, **glucocorticoids**, and **mineralocorticoids**, which is a separate endocrine pathway. *It causes hypogonadotropic hypogonadism* - While **hyperprolactinemia** *does* lead to **hypogonadotropic hypogonadism**, this option describes the *result* or *consequence* rather than the specific *mechanism* of how it causes amenorrhea. - The fundamental mechanism involves the direct disruption of **GnRH pulsatility** at the hypothalamic level, which then leads to the reduced secretion of gonadotropins. *It leads to decreased ovarian function due to low FSH and LH levels.* - This statement is a downstream effect, not the primary mechanism, just like the previous option. **Low FSH and LH levels** are indeed caused by the initial inhibition of GnRH. - **Decreased ovarian function** is a direct consequence of insufficient **gonadotropin stimulation**, preventing follicular development and estrogen production, which ultimately results in amenorrhea.

Question 469: After ejaculation, how long does it typically take for semen to liquefy?

A. 35 minutes
B. 30 minutes (Correct Answer)
C. 20 minutes
D. 25 minutes

Explanation: ***30 minutes*** - Semen undergoes a process called **liquefaction** after ejaculation, transforming from a coagulum into a liquid state. - This process is essential for **sperm motility** and **typically completes within 30 minutes** after collection. - While the normal range is 15-60 minutes, **30 minutes represents the typical/expected time** for complete liquefaction in standard semen analysis. *20 minutes* - While liquefaction begins shortly after ejaculation, 20 minutes is typically **too short** for complete liquefaction in most samples. - Incomplete liquefaction within this timeframe might suggest an underlying issue, though it's still within the early part of the normal range. *25 minutes* - Similar to 20 minutes, 25 minutes is generally **not sufficient time** for full liquefaction to be reliably complete in most normal semen samples. - While some samples may liquefy by this time, it is **not the typical timeframe** used as the standard reference. *35 minutes* - Although 35 minutes is still **within the normal range** (15-60 minutes), it is **not the typical time** referenced in standard semen analysis protocols. - The question asks for the **typical time**, which is **30 minutes**, not the outer limits of the normal range. - Liquefaction times consistently exceeding 60 minutes are considered **abnormal** and can affect fertility assessment.

Question 470: Which of the following cells are the target site for follicle-stimulating hormone (FSH) action?

A. Granulosa cells (Correct Answer)
B. Theca interna
C. Endometrium
D. Myometrium

Explanation: ***Granulosa cells*** - **FSH** acts on **granulosa cells** in the ovarian follicle, stimulating their proliferation and differentiation. - This action is crucial for **follicle development** and the production of **estrogen** by these cells, particularly through the **aromatase** enzyme. *Theca interna* - **Theca interna** cells are primarily stimulated by **luteinizing hormone (LH)**, not FSH. - They produce **androgens** (e.g., androstenedione) which are then converted to estrogen by granulosa cells. *Endometrium* - The **endometrium** is the inner lining of the uterus and is primarily responsive to **estrogen** and **progesterone**, which prepare it for implantation. - It does not have direct **FSH receptors** or synthesize reproductive hormones in response to FSH. *Myometrium* - The **myometrium** is the muscular wall of the uterus, responsible for contractions. - Its activity is regulated by hormones like **oxytocin** and **prostaglandins**, and it is not a direct target for **FSH**.

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

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