Endocrinology Practice Questions

Q: Which hormone stimulates the synthesis of milk proteins?

Prolactin (PRL). **Explanation:** **Prolactin (PRL)** is the primary hormone responsible for the **synthesis of milk proteins** (such as casein and lactalbumin) and the initiation of lactation (lactogenesis). It is secreted by the lactotrophs of the anterior pituitary. During pregnancy, high levels of estrogen and progesterone stimulate breast development but inhibit the actual secretion of milk. Postpartum, the sudden drop in these steroid hormones allows Prolactin to stimulate the mammary alveolar cells to produce milk. **Analysis of Incorrect Options:** * **Luteinizing hormone (LH):** A gonadotropin that triggers ovulation in females and stimulates testosterone production by Leydig cells in males. It has no direct role in milk synthesis. * **Thyroid-stimulating hormone (TSH):** Regulates the production of thyroid hormones (T3 and T4) from the thyroid gland to control basal metabolic rate. * **Growth hormone (GH):** While structurally similar to Prolactin and possessing some lactogenic properties, its primary role is promoting linear growth and protein synthesis via IGF-1. **High-Yield NEET-PG Pearls:** * **Dopamine** (Prolactin-Inhibiting Hormone) is the primary physiological regulator that keeps Prolactin levels low in non-pregnant individuals. * **Oxytocin** is responsible for the **milk-ejection reflex** (let-down reflex) via contraction of myoepithelial cells, whereas Prolactin is for **milk production**. * **Suckling** is the strongest stimulus for both Prolactin and Oxytocin release. * **Hyperprolactinemia** often presents with galactorrhea and secondary amenorrhea (due to inhibition of GnRH).

Q: A 45-year-old female patient, known diabetic on insulin therapy, presents for a routine general checkup. On examination, truncal obesity is noted. The sensitivity of the agent used in the treatment of this patient is enhanced by which of the following?

Adiponectin. The patient described is a diabetic on **insulin therapy**. The question asks which factor enhances the sensitivity of insulin. **1. Why Adiponectin is Correct:** Adiponectin is an adipokine secreted by adipose tissue [2]. It acts as a potent **insulin sensitizer**. It enhances insulin sensitivity by [1]: * Increasing fatty acid oxidation via activation of **AMP-activated protein kinase (AMPK)** in skeletal muscle and the liver. * Decreasing hepatic gluconeogenesis. * Increasing glucose uptake in muscles. In patients with truncal obesity (as seen in this case), adiponectin levels are typically **decreased**, contributing to insulin resistance [1]. Therefore, higher levels of adiponectin directly enhance the sensitivity of the insulin the patient is receiving. **2. Why Other Options are Incorrect:** * **Leptin:** While also an adipokine, its primary role is regulating energy balance and appetite (satiety signal) [2]. In obesity, "leptin resistance" occurs. It does not directly enhance insulin sensitivity in the same potent manner as adiponectin. * **Glucagon:** This is a counter-regulatory hormone. It opposes insulin action by promoting glycogenolysis and gluconeogenesis, thereby **decreasing** insulin effectiveness and raising blood glucose. * **Insulin:** Insulin does not enhance its own sensitivity; chronic high levels of insulin (hyperinflation) actually lead to the downregulation of receptors and **increased** insulin resistance. **Clinical Pearls for NEET-PG:** * **Adiponectin Paradox:** Unlike other adipokines (like Resistin or TNF-α), adiponectin levels are **inversely** correlated with body fat percentage (lower in obesity). * **Thiazolidinediones (TZDs):** Drugs like Pioglitazone work partly by increasing the expression and secretion of adiponectin. * **AMPK Activation:** This is the common pathway for both Adiponectin and Metformin to improve insulin sensitivity.

Q: Which of the following is NOT a physiologic change of thyroid metabolism during pregnancy?

TSH level is highest during the first trimester. **Explanation:** The correct answer is **D**. During pregnancy, thyroid physiology undergoes significant changes driven by rising levels of **Human Chorionic Gonadotropin (hCG)** and **Estrogen**. 1. **Why Option D is the correct (incorrect statement):** hCG shares a common alpha-subunit with TSH and can directly stimulate the TSH receptor. During the **first trimester**, hCG levels peak, leading to a transient increase in free T4. This rise in T4 exerts negative feedback on the pituitary, causing **TSH levels to reach their lowest point** (nadir) during the first trimester, not the highest. 2. **Why the other options are wrong (correct physiologic changes):** * **Option B:** High estrogen levels stimulate the liver to increase the synthesis of **Thyroxine-Binding Globulin (TBG)** and decrease its clearance. * **Option A:** Because TBG levels are elevated, more T4 and T3 are bound. To maintain a constant level of "free" (active) hormone, the total pool of thyroid hormones increases. Thus, **Total T4 and T3 are elevated**, while Free T4/T3 remain largely within normal limits. * **Option C:** hCG is a structural analog of TSH. At high concentrations (especially weeks 8–12), it acts as a weak thyrotropin, stimulating the thyroid gland. **High-Yield Clinical Pearls for NEET-PG:** * **Total T4** in pregnancy is roughly **1.5 times** the non-pregnant value. * The **TSH reference range is lower** in pregnancy (Lower limit ~0.1 mIU/L; Upper limit ~2.5–3.0 mIU/L in the first trimester). * **Iodine requirements increase** during pregnancy due to increased glomerular filtration rate (renal loss) and fetal transfer. * **Thyroid size** may increase slightly (goitrogenesis) due to hCG stimulation and iodine deficiency, but significant goiter is always pathologic.

Q: A 16-year-old female patient presents to the OPD with hirsutism and masculinization. Which of the following hormones of the adrenal cortex is the likely culprit?

Dehydroepiandrosterone (DHEA). ### Explanation **Correct Option: A. Dehydroepiandrosterone (DHEA)** The clinical presentation of **hirsutism** (excessive male-pattern hair growth) and **masculinization** (virilization) in a female indicates an excess of androgens. The adrenal cortex produces weak androgens, primarily **Dehydroepiandrosterone (DHEA)** and its sulfate form (DHEA-S), in the **Zona Reticularis**. In conditions like Congenital Adrenal Hyperplasia (CAH) or androgen-secreting adrenal tumors, these androgens are overproduced. While weak, they are converted peripherally into potent testosterone, leading to clitomegaly, deepening of the voice, and hirsutism. **Why other options are incorrect:** * **B. Aldosterone:** Produced in the *Zona Glomerulosa*, it regulates sodium and potassium balance. Excess leads to hypertension and hypokalemia (Conn’s Syndrome), not virilization. * **C. Cortisol:** Produced in the *Zona Fasciculata*, it regulates glucose metabolism and stress response. Excess (Cushing’s Syndrome) causes weight gain and "moon face." While Cushing’s can coexist with androgen excess, cortisol itself is not androgenic. * **D. Epinephrine:** This is a catecholamine produced by the **adrenal medulla**, not the cortex. It regulates the "fight or flight" response. **High-Yield NEET-PG Pearls:** * **Layers of Adrenal Cortex (Outer to Inner):** **G**lomerulosa (Salt/Aldosterone), **F**asciculata (Sugar/Cortisol), **R**eticularis (Sex/Androgens) — Mnemonic: **"GFR"**. * **DHEA-S** is the most specific marker for adrenal androgen production because the ovaries do not produce it. * The most common cause of virilizing CAH is **21-hydroxylase deficiency**, which shunts precursors toward the androgen pathway.

Q: Hypocalcemia due to calcitonin is caused by which of the following mechanisms?

Decreased bone resorption. **Explanation:** Calcitonin is a peptide hormone secreted by the **parafollicular cells (C-cells)** of the thyroid gland. Its primary physiological role is to lower plasma calcium levels, acting as a functional antagonist to Parathyroid Hormone (PTH). **Why Option B is Correct:** The most potent and immediate effect of calcitonin is the **inhibition of osteoclastic bone resorption**. Calcitonin binds to specific receptors on osteoclasts, leading to a decrease in their absorptive activity and a reduction in their formation rate. By preventing the breakdown of the bone matrix, it stops the release of calcium and phosphate into the blood, thereby inducing hypocalcemia. **Why Other Options are Incorrect:** * **Options A & D:** While calcitonin does have a minor effect on the kidneys by increasing the excretion of calcium and phosphate (by decreasing reabsorption in the tubules), this effect is **clinically insignificant** and transient compared to its profound effect on bone. * **Option C:** Calcitonin has no significant direct effect on the intestinal absorption of calcium. Intestinal absorption is primarily regulated by Vitamin D3 (Calcitriol). **High-Yield Clinical Pearls for NEET-PG:** * **Stimulus:** Calcitonin secretion is stimulated by an increase in plasma calcium levels and the hormone **Gastrin**. * **Clinical Use:** Due to its ability to inhibit osteoclasts, synthetic calcitonin (Salmon calcitonin) is used therapeutically in **Paget’s disease**, severe hypercalcemia, and postmenopausal osteoporosis. * **Tumor Marker:** Serum calcitonin is a highly specific tumor marker for **Medullary Thyroid Carcinoma (MTC)**. * **Escape Phenomenon:** Prolonged exposure to calcitonin leads to a downregulation of receptors, causing the hormone to lose its effectiveness over time.

Q: Early epiphyseal closure is seen with _________?

Estrogen. ### Explanation **Correct Option: C (Estrogen)** The primary hormone responsible for the fusion of the epiphyseal growth plates in both males and females is **Estrogen**. While Growth Hormone (GH) and Insulin-like Growth Factor-1 (IGF-1) drive linear bone growth, Estrogen acts on the estrogen receptors (ER-α) in the growth plate to trigger the maturation of chondrocytes and the eventual replacement of the cartilaginous plate with bone. In puberty, low levels of estrogen initially stimulate the "pubertal growth spurt," but as levels rise toward the end of puberty, they induce **epiphyseal senescence and closure**, effectively stopping linear growth. This is why conditions like precocious puberty (excess early estrogen) lead to short adult stature despite an initial growth spurt. **Why other options are incorrect:** * **LH and FSH (Options A & B):** These are gonadotropins secreted by the anterior pituitary. While they stimulate the gonads to produce sex steroids (estrogen/testosterone), they do not have a direct physiological effect on the epiphyseal plate closure themselves. * **Progesterone (Option D):** This hormone is primarily involved in the menstrual cycle and pregnancy maintenance; it has no significant role in bone maturation or epiphyseal fusion. **High-Yield Clinical Pearls for NEET-PG:** * **Aromatase Deficiency:** In individuals lacking the aromatase enzyme (which converts testosterone to estrogen), the epiphyses **fail to fuse**, leading to tall stature and continued growth into adulthood. * **Androgens:** Testosterone also contributes to bone growth, but its effect on plate closure is largely mediated by its peripheral conversion into estrogen. * **Thyroid Hormone:** Essential for bone age; deficiency (Hypothyroidism) causes significant **delayed bone age**. * **Glucocorticoids:** Excess levels (Cushing’s) inhibit bone growth and lead to stunted stature.

Q: Which of the following physiological states or substances promotes the secretion of Growth Hormone?

Glucagon. **Explanation:** Growth Hormone (GH) secretion is regulated by a complex interplay of hypothalamic factors (GHRH and Somatostatin) and metabolic signals. **Why Glucagon is Correct:** Glucagon is a potent stimulator of Growth Hormone secretion. While the exact mechanism is multifaceted, it is believed that glucagon stimulates the hypothalamus to release GHRH. Clinically, this is utilized in the **Glucagon Stimulation Test**, where glucagon is administered to provoke GH release to diagnose GH deficiency in children and adults. **Analysis of Incorrect Options:** * **Cortisol:** Chronic or high levels of glucocorticoids generally **inhibit** GH secretion by increasing somatostatin tone and decreasing GHRH sensitivity. * **REM Sleep:** GH secretion is characteristically associated with **Deep Sleep (Stage N3/Slow-wave sleep)**, typically occurring in the first 90 minutes of sleep. In contrast, GH secretion is inhibited during REM (Rapid Eye Movement) sleep. * **Glucose:** Hyperglycemia **inhibits** GH secretion. Conversely, hypoglycemia is one of the most potent physiological stimuli for GH release (used in the Insulin Tolerance Test). **High-Yield Clinical Pearls for NEET-PG:** * **Stimulators of GH:** Hypoglycemia, Fasting/Starvation, Exercise, Deep sleep, Amino acids (Arginine), and Ghrelin. * **Inhibitors of GH:** Hyperglycemia, Free fatty acids, Obesity, Somatostatin, and IGF-1 (via negative feedback). * **Gold Standard Test:** The **Insulin Tolerance Test (ITT)** is the gold standard for diagnosing GH deficiency, as it induces hypoglycemia to trigger GH release. * **Screening Test:** IGF-1 levels are used for screening acromegaly because GH is secreted in pulsatile bursts and has a short half-life.

Question 1

Which hormone stimulates the synthesis of milk proteins?

Accepted Answer

Prolactin (PRL)

Answer

Luteinizing hormone (LH)

Answer

Thyroid-stimulating hormone (TSH)

Answer

Growth hormone (GH)

Question 2

A diet deficient in calcium will result in what physiological change?

Accepted Answer

Production of parathyroid hormone and bone resorption

Answer

Stimulation of the thyroid gland

Answer

Increased ability to cross-link fibrin

Answer

Production of Calcitonin and a low blood calcium level

Question 3

A 45-year-old female patient, known diabetic on insulin therapy, presents for a routine general checkup. On examination, truncal obesity is noted. The sensitivity of the agent used in the treatment of this patient is enhanced by which of the following?

Accepted Answer

Adiponectin

Answer

Leptin

Answer

Glucagon

Answer

Insulin

Question 4

Which of the following is NOT a physiologic change of thyroid metabolism during pregnancy?

Accepted Answer

TSH level is highest during the first trimester

Answer

Increased levels of total T4 and T3

Answer

Elevated levels of serum TBG

Answer

hCG acts at the TSH receptor

Question 5

A 16-year-old female patient presents to the OPD with hirsutism and masculinization. Which of the following hormones of the adrenal cortex is the likely culprit?

Accepted Answer

Dehydroepiandrosterone (DHEA)

Answer

Aldosterone

Answer

Cortisol

Answer

Epinephrine

Question 6

Hypocalcemia due to calcitonin is caused by which of the following mechanisms?

Accepted Answer

Decreased bone resorption

Answer

Increased excretion in the kidney

Answer

Decreased intestinal absorption

Answer

Decreased renal reabsorption

Question 7

Early epiphyseal closure is seen with _________?

Accepted Answer

Estrogen

Answer

Luteinizing Hormone (LH)

Answer

Follicle-Stimulating Hormone (FSH)

Answer

Progesterone

Question 8

Regarding myxedema, which of the following statements is true EXCEPT:

Accepted Answer

Increased basal metabolic rate (BMR)

Answer

Swollen, edematous look of the face

Answer

Impotency, amenorrhea

Answer

Dullness, loss of memory

Question 9

Which of the following is NOT a physiological action of insulin?

Accepted Answer

Activation of lipoprotein lipase

Answer

Increased lipogenesis

Answer

Increased amino acid entry into the cell

Answer

Activation of key enzymes of glycolysis

Question 10

Which of the following physiological states or substances promotes the secretion of Growth Hormone?

Accepted Answer

Glucagon

Answer

Cortisol

Answer

REM sleep

Answer

Glucose

Endocrinology — MCQs

Endocrinology — MCQs

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