Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 21: Letrozole belongs to which pharmacological group?

A. Selective Estrogen Receptor Modulator (SERM)
B. Selective Estrogen Receptor Degrader (SERD)
C. Luteinizing Hormone-Releasing Hormone (LHRH) analogues
D. Aromatase inhibitors (Correct Answer)

Explanation: **Explanation:** **Letrozole** is a potent, third-generation **non-steroidal Aromatase Inhibitor (AI)**. The enzyme aromatase is responsible for the final step in estrogen synthesis—the conversion of androgens (androstenedione and testosterone) into estrogens (estrone and estradiol). By inhibiting this enzyme, Letrozole significantly reduces circulating estrogen levels, which is crucial in treating hormone-sensitive conditions. **Analysis of Options:** * **Aromatase Inhibitors (Correct):** Letrozole (along with Anastrozole and Exemestane) works by blocking the peripheral conversion of androgens to estrogens. In postmenopausal women, this is the primary source of estrogen. * **Selective Estrogen Receptor Modulators (SERMs):** Drugs like **Tamoxifen** and Raloxifene act as competitive antagonists or agonists at the estrogen receptor itself, rather than inhibiting estrogen production. * **Selective Estrogen Receptor Degraders (SERDs):** **Fulvestrant** is a SERD; it binds to and degrades the estrogen receptor, leading to its down-regulation. * **LHRH (GnRH) Analogues:** Drugs like **Leuprolide** and Goserelin act on the pituitary gland to initially stimulate and then suppress the release of LH and FSH, thereby reducing ovarian/testicular steroidogenesis. **NEET-PG High-Yield Pearls:** 1. **Drug of Choice (DOC):** Letrozole is currently the **DOC for ovulation induction** in Polycystic Ovary Syndrome (PCOS), surpassing Clomiphene citrate due to higher live-birth rates and fewer anti-estrogenic effects on the endometrium. 2. **Breast Cancer:** It is used as first-line adjuvant therapy for **ER-positive breast cancer in postmenopausal women**. 3. **Classification:** Remember the "A-L-E" mnemonic for AIs: **A**nastrozole, **L**etrozole (Type II/Non-steroidal/Reversible), and **E**xemestane (Type I/Steroidal/Irreversible).

Question 22: Adverse effects of insulin include all of the following except?

A. Edema
B. Weight loss (Correct Answer)
C. Lipodystrophy
D. Hypoglycemia

Explanation: The correct answer is Weight loss because insulin is an anabolic hormone [1, 2, 3]. Its primary physiological role is to promote the storage of glucose, lipids, and proteins [1, 2, 3].1. Why Weight Loss is the Correct Answer (The Exception):Insulin does not cause weight loss; rather, weight gain is a classic side effect. Insulin promotes lipogenesis (fat synthesis) and inhibits lipolysis [1]. Additionally, as insulin therapy effectively controls glycemia, it eliminates glucosuria (loss of calories through urine), leading to a net positive energy balance and subsequent weight gain.2. Analysis of Other Options:* Hypoglycemia (Option D): This is the most common and most serious adverse effect of insulin therapy, resulting from an overdose or mismatched carbohydrate intake [1, 2].* Lipodystrophy (Option C): This occurs at the site of injection. It can manifest as Lipoatrophy (immune-mediated loss of fat, rarer with human insulin) or Lipohypertrophy (fat accumulation due to the local anabolic effect of insulin), which can be prevented by rotating injection sites.* Edema (Option A): Known as "Insulin Edema," this occurs due to insulin’s effect on the kidneys, where it promotes sodium and water retention in the distal tubules. It is usually transient and seen during the initiation of intensive therapy.Clinical Pearls for NEET-PG:* Hypokalemia: Insulin shifts potassium into cells (by activating Na+/K+ ATPase) [1, 2]. It is used therapeutically in hyperkalemia but can be an adverse effect during the treatment of DKA.* Somogyi Effect: Post-hypoglycemic hyperglycemia caused by a counter-regulatory hormonal surge.* Local Allergy: Usually a Type I hypersensitivity reaction to contaminants or the insulin molecule itself.

Question 23: Hypoglycemia is caused by which of the following?

A. Alcohol intoxication (Correct Answer)
B. Thiazide
C. Diazoxide
D. Metoclopramide

Explanation: **Explanation:** **1. Why Alcohol Intoxication is Correct:** Alcohol (Ethanol) metabolism increases the **NADH/NAD+ ratio** in the liver. High levels of NADH shift the equilibrium of pyruvate toward lactate and oxaloacetate toward malate. Since pyruvate and oxaloacetate are essential precursors for **gluconeogenesis**, their depletion inhibits the liver's ability to produce glucose. This is particularly dangerous in fasting states or in individuals with depleted glycogen stores, leading to profound fasting hypoglycemia. **2. Why the Other Options are Incorrect:** * **Thiazides:** These diuretics are known to cause **hyperglycemia**. They inhibit insulin release from pancreatic beta cells (via potassium channel activation) and decrease peripheral glucose utilization. * **Diazoxide:** This is a potassium channel opener used specifically to treat hyperinsulinism. By keeping $K_{ATP}$ channels open, it hyperpolarizes beta cells and **inhibits insulin secretion**, thereby causing hyperglycemia. * **Metoclopramide:** This is a D2 receptor antagonist used as a prokinetic and antiemetic. It has no direct effect on blood glucose levels, though it may affect the timing of glucose absorption by increasing gastric emptying. **3. High-Yield Clinical Pearls for NEET-PG:** * **Disulfiram-like reaction:** Remember the drugs that cause this when taken with alcohol (e.g., Metronidazole, Cefotetan, Sulfonylureas). * **Drug-induced Hypoglycemia:** Other common culprits include Salicylates (in children), Beta-blockers (which also mask hypoglycemic symptoms), and Quinine. * **Drug-induced Hyperglycemia:** Remember the mnemonic **"S-T-E-P-D"**: **S**teroids, **T**hiazides, **E**strogen, **P**henytoin, and **D**iazoxide.

Question 24: Which antihormone is used in the management of infertility?

A. Mifepristone
B. Clomifene (Correct Answer)
C. Danazol
D. Finasteride

Explanation: **Explanation:** **Clomifene** is the correct answer because it is a **Selective Estrogen Receptor Modulator (SERM)** specifically used as a first-line agent for inducing ovulation in infertility associated with anovulatory cycles (e.g., Polycystic Ovary Syndrome) [2]. **Mechanism of Action:** Clomifene acts as a competitive antagonist at estrogen receptors in the **hypothalamus and anterior pituitary**. By blocking the negative feedback of endogenous estrogens, it triggers an increase in the pulsatile secretion of **GnRH, FSH, and LH**. The rise in FSH stimulates follicular growth, leading to a mid-cycle LH surge and subsequent ovulation [2]. **Analysis of Incorrect Options:** * **Mifepristone (A):** A progesterone receptor antagonist used primarily for medical termination of pregnancy (MTP) and Cushing’s syndrome; it prevents rather than aids conception. * **Danazol (C):** An impeded androgen used in endometriosis and hereditary angioedema. It suppresses the pituitary-ovarian axis, leading to anovulation [1]. * **Finasteride (D):** A 5-alpha-reductase inhibitor used in Benign Prostatic Hyperplasia (BPH) and male pattern baldness; it has no role in female infertility. **High-Yield Clinical Pearls for NEET-PG:** * **Side Effects:** The most common side effect of Clomifene is **multiple pregnancies** (mostly twins) and ovarian hyperstimulation syndrome (OHSS) [2]. * **Contraindication:** It should not be used in patients with ovarian cysts or liver disease [2]. * **Other SERMs:** Remember **Tamoxifen** (used in breast cancer) and **Raloxifene** (used in postmenopausal osteoporosis) [3]. Unlike Clomifene, Raloxifene does not increase the risk of endometrial cancer [4].

Question 25: Which of the following is a side effect of steroids due to their mineralocorticoid component?

A. Skin striae
B. Hypertension (Correct Answer)
C. Osteoporosis
D. Moon face

Explanation: **Explanation:** Glucocorticoids (like Prednisolone or Hydrocortisone) possess varying degrees of cross-reactivity with **mineralocorticoid receptors**. The correct answer is **Hypertension** because it is a direct consequence of this mineralocorticoid activity. 1. **Mechanism of Hypertension:** Mineralocorticoid action (similar to Aldosterone) occurs in the distal convoluted tubules of the kidney. It leads to **Sodium ($Na^+$) and water retention** and **Potassium ($K^+$) excretion**. The resulting expansion of extracellular fluid volume and hypernatremia lead to an increase in blood pressure. 2. **Incorrect Options:** * **Skin striae, Osteoporosis, and Moon face** are all side effects resulting from the **Glucocorticoid component** (metabolic and catabolic effects). * **Skin striae:** Due to protein catabolism and loss of collagen in the dermis. * **Osteoporosis:** Due to decreased osteoblast activity, decreased calcium absorption, and increased PTH sensitivity. * **Moon face:** Due to redistribution of fat (lipogenesis in specific areas). **High-Yield Clinical Pearls for NEET-PG:** * **Dexamethasone and Betamethasone** have the highest glucocorticoid potency but **zero mineralocorticoid activity**, making them safer for patients with heart failure or hypertension. * **Fludrocortisone** is the steroid with the highest mineralocorticoid-to-glucocorticoid ratio, used primarily in Addison’s disease. * **Electrolyte Triad of Mineralocorticoid Excess:** Hypertension, Hypernatremia, and Hypokalemic Metabolic Alkalosis.

Question 26: Which of the following statements about methimazole and propylthiouracil is incorrect?

A. Methimazole is secreted into milk.
B. Methimazole has a larger volume of distribution than propylthiouracil.
C. Methimazole is more protein-bound than propylthiouracil. (Correct Answer)
D. All of the above are correct differences.

Explanation: This question tests your knowledge of the pharmacokinetic differences between the two primary Thionamides used in hyperthyroidism. ### **Explanation of the Correct Answer** **Option C is incorrect** because **Propylthiouracil (PTU) is more protein-bound (approx. 60–80%) than Methimazole (virtually 0%).** In pharmacology, protein binding significantly influences a drug's distribution and its ability to cross biological barriers. Because Methimazole has negligible protein binding, it has a larger volume of distribution and crosses the placenta and enters breast milk more readily than PTU. ### **Analysis of Other Options** * **Option A (Correct statement):** Methimazole is secreted into milk in higher concentrations than PTU due to its low protein binding. While both are generally considered safe in low doses during lactation, PTU was historically preferred for this reason. * **Option B (Correct statement):** Methimazole has a **larger volume of distribution (Vd)** because it does not bind to plasma proteins, allowing it to distribute freely into tissues. PTU, being highly protein-bound, remains more confined to the vascular compartment. ### **High-Yield NEET-PG Clinical Pearls** * **Potency:** Methimazole is **10 times more potent** than PTU and has a longer half-life, allowing for once-daily dosing. * **Mechanism:** Both inhibit Thyroid Peroxidase (TPO). However, **PTU uniquely inhibits the peripheral conversion of T4 to T3** (via 5'-deiodinase inhibition), making it the drug of choice in **Thyroid Storm**. * **Teratogenicity:** Methimazole is associated with **Aplasia Cutis** and Choanal atresia; thus, **PTU is preferred in the 1st trimester** of pregnancy. Methimazole is preferred in the 2nd and 3rd trimesters to avoid PTU-induced hepatotoxicity. * **Side Effects:** The most serious side effect for both is **Agranulocytosis** (usually occurs within the first 3 months).

Question 27: Sulfonylureas act by:

A. Decreasing glucagon secretion from the pancreas
B. Decreasing insulin secretion from the pancreas
C. Increasing gluconeogenesis
D. Increasing insulin secretion from the pancreas (Correct Answer)

Explanation: ### Explanation **Mechanism of Action (Why D is correct):** Sulfonylureas (e.g., Glibenclamide, Glipizide, Glimepiride) are **insulin secretagogues**. They act by binding to a specific **Sulfonylurea Receptor-1 (SUR1)** subunit associated with the **ATP-sensitive potassium ($K_{ATP}$) channels** on the pancreatic beta-cell membrane. 1. Binding leads to the **closure** of these $K^+$ channels. 2. This causes cell membrane **depolarization**. 3. Depolarization opens **voltage-gated $Ca^{2+}$ channels**, leading to calcium influx. 4. Increased intracellular calcium triggers the **exocytosis of insulin** granules. **Analysis of Incorrect Options:** * **Option A:** While insulin has a paracrine effect that may indirectly suppress glucagon, the primary and direct mechanism of Sulfonylureas is stimulating insulin release, not inhibiting glucagon. * **Option B:** This is the opposite of their physiological effect. Sulfonylureas increase insulin secretion; drugs like Diazoxide or Somatostatin decrease it. * **Option C:** Sulfonylureas do not primarily affect gluconeogenesis. **Metformin** (a Biguanide) is the drug that primarily acts by inhibiting hepatic gluconeogenesis. **NEET-PG High-Yield Clinical Pearls:** * **Prerequisite:** Sulfonylureas require **functional beta-cells** to work; hence, they are ineffective in Type 1 Diabetes Mellitus. * **Adverse Effects:** The most common side effect is **hypoglycemia** (especially with long-acting agents like Glibenclamide) and **weight gain**. * **Disulfiram-like reaction:** Classically associated with first-generation sulfonylureas like **Chlorpropamide**. * **Safety:** **Glipizide** is preferred in patients with mild-to-moderate renal impairment as it is primarily metabolized by the liver.

Question 28: In oral contraceptive pills (OCP), which of the following is used as the estrogen component?

A. Ethinyl estradiol (Correct Answer)
B. Norethisterone
C. Ethynodiol diacetate
D. Allyloestranol

Explanation: **Explanation:** **1. Why Ethinyl Estradiol is Correct:** Ethinyl estradiol (EE) is the most common estrogenic component used in combined oral contraceptive pills (COCPs). Natural estradiol has very low oral bioavailability due to extensive first-pass metabolism in the liver. The addition of an **ethinyl group at the C17 position** makes the molecule resistant to first-pass metabolism, significantly increasing its oral potency and duration of action. Its primary role in OCPs is to inhibit the release of **FSH (Follicle Stimulating Hormone)**, thereby preventing follicular development and providing cycle control. **2. Why Other Options are Incorrect:** * **B. Norethisterone:** This is a first-generation **progestin** (19-nortestosterone derivative), not an estrogen. It acts by thickening cervical mucus and inhibiting LH. * **C. Ethynodiol diacetate:** This is also a **progestin** (prodrug of norethisterone) used in some contraceptive formulations. * **D. Allyloestranol:** This is a synthetic **progestogen** primarily used to prevent threatened or recurrent miscarriage; it is not a standard component of OCPs. **3. High-Yield NEET-PG Pearls:** * **Mestranol:** Another estrogen used in OCPs; it is a prodrug that must be converted to ethinyl estradiol in the liver. * **Mechanism of Action:** Estrogen inhibits FSH (prevents ovulation), while Progestin inhibits LH (prevents LH surge) and renders cervical mucus hostile to sperm. * **Non-contraceptive benefits:** OCPs reduce the risk of **Ovarian and Endometrial cancers**, but may slightly increase the risk of Breast and Cervical cancers. * **Contraindications:** History of thromboembolism, heavy smokers (>35 years), and undiagnosed vaginal bleeding.

Question 29: What is the recommended dose of Testosterone for hypogonadal males?

A. 25-50 mg IM weekly
B. 50-75 mg IM weekly
C. 75-100 mg IM weekly (Correct Answer)
D. 150-200 mg IM weekly

Explanation: **Explanation:** The primary goal of testosterone replacement therapy (TRT) in hypogonadal males is to replicate physiological serum testosterone levels (typically 300–1000 ng/dL). **Why Option C is correct:** The standard therapeutic regimen for **Testosterone Enanthate or Cypionate** (the most commonly used esters) is **75–100 mg administered intramuscularly (IM) once weekly**, or alternatively, 150–200 mg every two weeks. This dosage effectively maintains stable trough levels while minimizing the "rollercoaster effect" (significant peaks and troughs in mood and libido) often seen with longer dosing intervals. **Analysis of Incorrect Options:** * **Options A & B (25–75 mg weekly):** These doses are generally considered sub-therapeutic for an adult male. While they may be used during the initiation of puberty in adolescents, they are insufficient to maintain secondary sexual characteristics and bone mineral density in adult hypogonadism. * **Option D (150–200 mg weekly):** This is considered a supraphysiological dose. While 200 mg is often given every *two* weeks, giving it *weekly* increases the risk of side effects like erythrocytosis (elevated hematocrit), acne, and gynecomastia due to peripheral aromatization into estrogen. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Choice:** IM is preferred for cost-effectiveness and reliability; however, oral testosterone (undecanoate) must be taken with high-fat meals to bypass first-pass metabolism via the lymphatic system. * **Monitoring:** Always monitor **Hematocrit** (risk of polycythemia) and **PSA** (Prostate-Specific Antigen) before and during treatment. * **Contraindications:** Carcinoma of the prostate or breast and severe untreated obstructive sleep apnea. * **Side Effect:** Azoospermia (due to negative feedback inhibition of GnRH and FSH).

Question 30: Flutamide is an:

A. Anti-convulsant
B. Anti-androgen (Correct Answer)
C. Anti-progestin
D. Anti-oestrogen

Explanation: **Explanation:** **Flutamide** is a potent, non-steroidal **competitive antagonist at androgen receptors**. It works by blocking the binding of dihydrotestosterone (DHT) and testosterone to their specific receptors in target tissues. Because it inhibits the action of male sex hormones, it is classified as an **Anti-androgen**. **Analysis of Options:** * **Option B (Correct):** Flutamide blocks androgen receptors. Its primary clinical utility is in the management of **Carcinoma Prostate**, often used in combination with GnRH agonists (like Leuprolide) to prevent the "testosterone flare" phenomenon. * **Option A (Incorrect):** Anti-convulsants (e.g., Phenytoin, Valproate) act on ion channels or GABA receptors to prevent seizures; Flutamide has no such activity. * **Option C (Incorrect):** Anti-progestins (e.g., Mifepristone) block progesterone receptors and are used for medical abortion. * **Option D (Incorrect):** Anti-oestrogens (e.g., Tamoxifen, Clomiphene) block estrogen receptors and are used in breast cancer or infertility. **High-Yield NEET-PG Pearls:** 1. **Mechanism:** Pure non-steroidal androgen receptor blocker. 2. **Clinical Use:** Metastatic Prostate Cancer and sometimes in female hirsutism (though limited by toxicity). 3. **Side Effects:** The most significant adverse effect is **hepatotoxicity** (requires periodic LFT monitoring). It also causes **gynecomastia** due to increased peripheral conversion of androgens to estrogens. 4. **Related Drugs:** Bicalutamide and Enzalutamide are newer analogs with longer half-lives and less hepatotoxicity, making them preferred over Flutamide in modern practice.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

Insulin and Oral Hypoglycemic Agents

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Adrenocorticosteroids

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Sex Hormones: Estrogens and Progestins

Practice Questions

Androgens and Anabolic Steroids

Practice Questions

Hormonal Contraceptives

Practice Questions

Drugs Affecting Calcium Metabolism

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Drugs for Osteoporosis

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Pharmacological Management of Obesity

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