Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 91: Decreased level of testosterone results in all EXCEPT:

A. Loss of libido
B. Infertility
C. Decreased frequency of sexual intercourse
D. Increased muscle mass (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Increased muscle mass**. This is because testosterone is a potent **anabolic hormone**. It promotes protein synthesis and the growth of skeletal muscle by binding to androgen receptors. Therefore, a decrease in testosterone levels leads to **muscle atrophy (decreased muscle mass)** and an increase in body fat, rather than an increase in muscle mass. **Analysis of Options:** * **A & C (Loss of libido & Decreased frequency of intercourse):** Testosterone is the primary hormone responsible for male sexual drive (libido). Low levels directly result in reduced sexual desire and a subsequent decrease in the frequency of sexual activity. * **B (Infertility):** High intratesticular concentrations of testosterone are essential for **spermatogenesis**. A deficiency impairs the maturation of sperm cells, leading to oligospermia or azoospermia, and ultimately, infertility. **Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Testosterone acts via nuclear receptors to alter gene expression. * **Anabolic vs. Androgenic:** While "androgenic" refers to masculinizing effects (hair growth, voice deepening), "anabolic" refers to tissue-building effects (muscle and bone mass). * **Secondary Hypogonadism:** Low testosterone can also lead to osteoporosis, gynecomastia, and loss of secondary sexual characteristics (e.g., decreased facial hair). * **Hormonal Regulation:** Testosterone provides negative feedback to the hypothalamus (GnRH) and anterior pituitary (LH). In primary hypogonadism (testicular failure), LH levels will be elevated.

Question 92: Naturally occurring estrogens are:

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

Explanation: **Explanation:** The question asks for naturally occurring estrogens. While the options include several estrogens, the key is identifying which among them are synthesized naturally within the human body. **1. Why Estriol (Option C) is correct:** Estrogens are a group of steroid hormones. The three major naturally occurring estrogens in females are **Estrone (E1)**, **Estradiol (E2)**, and **Estriol (E3)**. * **Estriol (E3)** is the primary estrogen produced during **pregnancy** by the syncytiotrophoblast of the placenta. It is synthesized from 16-OH DHEAS produced by the fetal liver, making it a crucial marker of fetal well-being. **2. Analysis of Incorrect Options:** * **Estrone (E1) & Estradiol (E2):** These are also naturally occurring estrogens. However, in the context of multiple-choice questions where only one "best" answer is sought (or if the question implies the most abundant form in specific states), it is important to note that **Estradiol** is the most potent and dominant in non-pregnant premenopausal women, while **Estrone** is dominant in postmenopausal women. *Note: In many standard NEET-PG patterns, if A, B, and C are all natural estrogens, the question might be flawed or intended to highlight Estriol’s specific association with pregnancy.* * **Pregnanediol (Option D):** This is **not** an estrogen. It is the inactive urinary metabolite of **Progesterone**. Measuring urinary pregnanediol levels is an indirect way to estimate progesterone production in the body. **High-Yield NEET-PG Pearls:** * **Potency Order:** Estradiol (E2) > Estrone (E1) > Estriol (E3). * **E1 (Estrone):** Predominant in **menopause** (produced by peripheral conversion in adipose tissue). * **E2 (Estradiol):** Predominant in **reproductive years** (produced by granulosa cells). * **E3 (Estriol):** Predominant in **pregnancy** (Placental origin). * **E4 (Estetrol):** A fourth natural estrogen produced only during pregnancy by the fetal liver.

Question 93: Which of the following is NOT related to granulosa cells?

A. It has no blood supply.
B. In the first half of the cycle, it has no steroidogenic function. (Correct Answer)
C. Granulosa cells produce activin and inhibin.
D. Estrogen stimulates the proliferation of granulosa cells.

Explanation: ### Explanation The correct answer is **B**, as the statement "In the first half of the cycle, it has no steroidogenic function" is **incorrect**. Granulosa cells are active steroidogenic cells throughout the entire ovarian cycle. **1. Why Option B is the correct choice (The False Statement):** In the follicular phase (first half), granulosa cells perform a vital steroidogenic function via the **Two-Cell, Two-Gonadotropin Theory**. While they cannot produce androgens (due to lack of 17α-hydroxylase), they contain the enzyme **aromatase**. Under the influence of FSH, they convert androstenedione (produced by theca cells) into **estradiol**. Therefore, saying they have no steroidogenic function is physiologically inaccurate. **2. Analysis of Other Options:** * **Option A:** Granulosa cells are **avascular** until ovulation occurs. They are separated from the vascularized theca interna by a basement membrane (lamina propria). Blood vessels only invade the granulosa layer after the LH surge to form the corpus luteum. * **Option C:** Granulosa cells are the primary source of **Inhibin (A and B)** and **Activin**, which provide feedback to the anterior pituitary to regulate FSH secretion. * **Option D:** Estrogen exerts a local **mitogenic effect** on granulosa cells. It acts synergistically with FSH to increase the number of granulosa cells and the expression of FSH receptors. **Clinical Pearls for NEET-PG:** * **Two-Cell Theory:** Theca cells (LH) produce Androgens $\rightarrow$ Granulosa cells (FSH) produce Estrogens. * **Inhibin B** is highest in the follicular phase; **Inhibin A** is highest in the luteal phase. * **Call-Exner Bodies:** Small fluid-filled spaces between granulosa cells, a pathognomonic histological feature of **Granulosa Cell Tumors**.

Question 94: Antimullerian hormone is secreted by which cells?

A. Granulosa cells
B. Leydig cells
C. Sertoli cells (Correct Answer)
D. None of the above

Explanation: **Explanation:** **Anti-Müllerian Hormone (AMH)**, also known as Müllerian Inhibiting Substance (MIS), is a glycoprotein belonging to the TGF-β superfamily. Its primary physiological role occurs during male fetal development. **Why Sertoli Cells are correct:** In males, AMH is secreted by the **fetal Sertoli cells** starting around the 8th week of gestation. Its critical function is to cause the regression of the **Müllerian ducts** (paramesonephric ducts), which would otherwise develop into the uterus, fallopian tubes, and upper vagina. This ensures the fetus develops male internal genitalia. **Analysis of Incorrect Options:** * **Granulosa cells:** While AMH is produced by granulosa cells of pre-antral and small antral follicles in adult females (used clinically to measure ovarian reserve), the classic physiological context of AMH secretion—especially regarding sexual differentiation—is the fetal Sertoli cell. In the context of this standard question, Sertoli cells are the primary answer. * **Leydig cells:** These cells secrete **Testosterone**, which is responsible for the stabilization of Wolffian ducts (internal male genitalia) and the development of external male genitalia (via DHT). They do not produce AMH. **High-Yield Clinical Pearls for NEET-PG:** * **Persistent Müllerian Duct Syndrome (PMDS):** Occurs due to a deficiency of AMH or a mutation in its receptor. The patient is a genotypic male (46,XY) with bilateral cryptorchidism and the presence of a uterus/fallopian tubes. * **Ovarian Reserve Marker:** In adult females, serum AMH levels are the most sensitive marker for ovarian reserve as they are independent of the menstrual cycle (unlike FSH). * **Source Summary:** Sertoli cells = AMH (Müllerian regression); Leydig cells = Testosterone (Wolffian stabilization).

Question 95: The pH of the vagina in adults is:

A. 3.5 - 4.5
B. 4.5 - 5.5 (Correct Answer)
C. 5.5 - 6.5
D. 6.5 - 7.5

Explanation: The vaginal pH is a critical physiological parameter that changes throughout a woman's life cycle. In a healthy adult female of reproductive age, the normal vaginal pH typically ranges from **4.5 to 5.5** (though some texts cite 3.8–4.5, standard medical entrance exams often follow the 4.5–5.5 range as the physiological baseline for adults). ### Why Option B is Correct The acidic environment is maintained by **Döderlein’s bacilli** (Lactobacilli). Under the influence of **estrogen**, the vaginal epithelium thickens and accumulates **glycogen**. Lactobacilli ferment this glycogen into **lactic acid**, lowering the pH. This acidity serves as a primary innate immune defense, inhibiting the growth of pathogenic bacteria and fungi. ### Why Other Options are Incorrect * **Option A (3.5 - 4.5):** While this is the range for a highly acidic, healthy state, most standard clinical references for "adult range" in a broad population context align closer to 4.5–5.5. * **Option C & D (5.5 - 7.5):** These ranges are considered **alkaline/neutral**. A pH >4.5 in a reproductive-age woman is often pathological, indicating a loss of Lactobacilli. ### High-Yield Clinical Pearls for NEET-PG 1. **Age Variations:** * **Pre-puberty & Post-menopause:** The pH is **neutral or alkaline (6.0–7.0)** due to low estrogen levels and lack of glycogen. * **Pregnancy:** The pH becomes **more acidic** (approx. 3.5–4.0) due to high estrogen levels. 2. **Diagnostic Utility:** * **Bacterial Vaginosis (BV) & Trichomoniasis:** Vaginal pH **increases (>4.5)**. * **Vulvovaginal Candidiasis:** Vaginal pH typically remains **normal (<4.5)**. 3. **Semen Influence:** Semen is alkaline (pH 7.2–8.0), which temporarily neutralizes vaginal acidity to protect sperm motility.

Question 96: What is the major estrogen in normal adult women?

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

Explanation: **Explanation:** In normal, non-pregnant adult women of reproductive age, **Estradiol (E2)** is the predominant and most potent circulating estrogen. It is primarily secreted by the granulosa cells of the ovarian follicles under the influence of FSH. Its potency is approximately 12 times that of estrone and 80 times that of estriol, making it the major driver of the female reproductive cycle and secondary sexual characteristics. **Analysis of Options:** * **Option A (Estradiol - E2):** Correct. It is the major estrogen during the reproductive years. * **Option B (Estrone - E1):** This is the predominant estrogen in **postmenopausal** women. It is weaker than estradiol and is primarily formed through the peripheral aromatization of androstenedione in adipose tissue. * **Option C (Estriol - E3):** This is the predominant estrogen during **pregnancy**. It is produced by the placenta using precursors (16-OH DHEAS) from the fetal liver and adrenal glands. It is the least potent of the three estrogens. * **Option D:** Incorrect, as Estradiol is the established major estrogen. **High-Yield NEET-PG Pearls:** 1. **Potency Order:** Estradiol (E2) > Estrone (E1) > Estriol (E3). (Mnemonic: **2 > 1 > 3**) 2. **Source:** The "Two-Cell, Two-Gonadotropin" theory explains its synthesis: LH stimulates Theca cells to produce androgens, which FSH then helps Granulosa cells convert into Estradiol via the enzyme **aromatase**. 3. **Clinical Marker:** Serum Estriol levels are used in the "Triple/Quadruple Screen" to monitor fetal well-being; low levels may indicate placental insufficiency or fetal anomalies.

Question 97: The karyotype in testicular feminising syndrome is?

A. XX
B. XY (Correct Answer)
C. XXY
D. XXXY

Explanation: **Explanation:** **Testicular Feminization Syndrome**, now more commonly known as **Androgen Insensitivity Syndrome (AIS)**, is a condition where an individual is genetically male but phenotypically female. 1. **Why XY is Correct:** In AIS, the individual has a **46, XY karyotype**. The underlying pathology is a mutation in the **androgen receptor gene** (located on the X chromosome). Although the testes develop normally (due to the SRY gene) and secrete testosterone, the peripheral tissues cannot respond to it. Consequently, the external genitalia develop along female lines. However, because the testes still secrete **Müllerian Inhibiting Substance (MIS)**, internal female structures (uterus, fallopian tubes, upper vagina) are absent. 2. **Why Other Options are Incorrect:** * **XX:** This is a normal female karyotype. In cases of virilization (like Congenital Adrenal Hyperplasia), an XX individual may appear male, but this is the opposite of AIS. * **XXY:** This is the karyotype for **Klinefelter Syndrome**. These individuals have a male phenotype, small firm testes, and infertility, but they do not exhibit the complete feminization seen in AIS. * **XXXY:** This is a rare variant of Klinefelter Syndrome with more severe intellectual disability and physical abnormalities. **High-Yield Clinical Pearls for NEET-PG:** * **Phenotype:** Tall, attractive female with a "blind-ending vagina" and absent uterus. * **Pubic/Axillary Hair:** Characteristically **absent or scanty** (due to androgen resistance). * **Gonads:** Undescended testes are present (often in the inguinal canal or labia majora). These must be removed after puberty to prevent **gonadoblastoma/dysgerminoma**. * **Hormonal Profile:** High Testosterone, High LH, and normal to high Estrogen (via peripheral conversion).

Question 98: What is the increasing order of potency of estrogens (least potent to most potent)?

A. Estrone (E1), Estriol (E3), Estradiol (E2)
B. Estrone (E1), Estradiol (E2), Estriol (E3)
C. Estriol (E3), Estrone (E1), Estradiol (E2) (Correct Answer)
D. Estradiol (E2), Estrone (E1), Estriol (E3)

Explanation: **Explanation:** The potency of estrogens is determined by their affinity for estrogen receptors (ER-α and ER-β) and the duration of the receptor-hormone complex activation. 1. **Estradiol (E2):** The most potent and primary estrogen in non-pregnant females of reproductive age. It is produced mainly by the granulosa cells of the ovaries. 2. **Estrone (E1):** Possesses intermediate potency (about 1/10th of E2). It is the predominant estrogen post-menopause, derived primarily from the peripheral conversion of androstenedione in adipose tissue. 3. **Estriol (E3):** The least potent estrogen (about 1/100th of E2). It is produced in significant quantities only during pregnancy by the syncytiotrophoblast of the placenta. Therefore, the increasing order of potency is **Estriol (E3) < Estrone (E1) < Estradiol (E2)**. **Analysis of Incorrect Options:** * **Options A & B:** Incorrectly place Estrone or Estriol as more potent than Estradiol. * **Option D:** Incorrectly suggests Estradiol is the least potent, whereas it is the most biologically active form. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Potency:** **"E3 < E1 < E2"** (Count the syllables/numbers: 3 is the weakest, 2 is the strongest). * **Source of E3:** Estriol is a marker of fetal well-being; its synthesis requires the fetal liver and adrenal glands (DHEAS) and the placenta. * **PCOS Connection:** In Polycystic Ovary Syndrome, there is an increased **E1:E2 ratio** due to the peripheral conversion of androgens in adipose tissue. * **Menopause:** Estrone (E1) becomes the dominant circulating estrogen.

Question 99: Which of the following features characterizes the secretory phase of the menstrual cycle?

A. It precedes ovulation.
B. It depends on progesterone secretion by the corpus luteum. (Correct Answer)
C. It coincides with the development of ovarian follicles.
D. It coincides with a rapid drop in estrogen levels.

Explanation: The menstrual cycle consists of the ovarian and uterine cycles. The **secretory phase** of the uterine cycle corresponds to the **luteal phase** of the ovarian cycle. ### **Explanation of the Correct Answer** **Option B** is correct because, after ovulation, the ruptured follicle transforms into the **corpus luteum**. This structure primarily secretes **progesterone** (and some estrogen). Progesterone acts on the endometrium to increase its vascularity, stimulate the growth of tortuous "corkscrew" glands, and promote glycogen storage. These changes prepare the uterus for the implantation of a fertilized ovum. ### **Analysis of Incorrect Options** * **Option A:** The secretory phase occurs **after** ovulation (Days 15–28). The phase preceding ovulation is the proliferative phase. * **Option C:** Follicular development occurs during the **follicular phase** (proliferative phase of the uterus), driven by FSH. In the secretory phase, the follicle has already ruptured. * **Option D:** While there is a transient dip in estrogen immediately after ovulation, the secretory phase is characterized by a **second rise** in estrogen alongside high progesterone levels. A "rapid drop" in both hormones only occurs at the very end of the phase, triggering menstruation. ### **NEET-PG High-Yield Pearls** * **Fixed Duration:** The secretory/luteal phase is constant at **14 days**. Variations in cycle length are usually due to the proliferative phase. * **Histology:** The presence of **sub-nuclear vacuoles** in the endometrial epithelium is the earliest histological sign of the secretory phase (occurring around day 16-17). * **Thermogenic Effect:** Progesterone increases the **Basal Body Temperature (BBT)** by 0.5–1.0°F, a clinical marker that ovulation has occurred.

Question 100: What is the approximate time taken for spermatogenesis?

A. 50-60 days
B. 60-70 days
C. 70-80 days (Correct Answer)
D. 80-90 days

Explanation: **Explanation:** Spermatogenesis is the complex process by which primitive germ cells (spermatogonia) develop into mature spermatozoa. In humans, this process occurs within the seminiferous tubules of the testes and follows a highly regulated chronological sequence. **Why Option C is Correct:** The total duration of spermatogenesis in humans is approximately **74 days** (commonly cited as **70–80 days** in standard textbooks like Guyton and Ganong). This timeline includes the progression from a Type A spermatogonium through primary and secondary spermatocytes, spermatids, and finally, mature spermatozoa. Following this, an additional 10–14 days are required for the sperm to traverse the epididymis and undergo functional maturation (motility development), bringing the total time from initiation to ejaculation to about 90 days. **Why Other Options are Incorrect:** * **Option A (50-60 days):** This is too short for human spermatogenesis; such durations are more characteristic of certain laboratory rodents (e.g., rats take ~52 days). * **Option B (60-70 days):** While closer, it underestimates the standard physiological timeframe of 74 days. * **Option D (80-90 days):** This range exceeds the actual time spent within the seminiferous tubules, though it may reflect the total time including epididymal transit. **NEET-PG High-Yield Pearls:** 1. **Spermiogenesis:** This is the final phase of spermatogenesis where *spermatids* transform into *spermatozoa* (no cell division occurs here). 2. **Hormonal Control:** LH stimulates **Leydig cells** to produce Testosterone; FSH stimulates **Sertoli cells** to support spermatogenesis and produce Inhibin B. 3. **Blood-Testis Barrier:** Formed by tight junctions between Sertoli cells, protecting developing sperm from the immune system. 4. **Temperature:** Spermatogenesis requires a temperature $2-3^\circ\text{C}$ lower than core body temperature.

Practice by Chapter

Male Reproductive Physiology

Practice Questions

Spermatogenesis and Sperm Function

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Female Reproductive Physiology

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Menstrual Cycle

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Ovulation and Fertilization

Practice Questions

Physiology of Pregnancy

Practice Questions

Parturition

Practice Questions

Lactation

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Sexual Differentiation and Development

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Reproductive Aging

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