Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 91: What is the drug of choice for thyroid storm?

A. Thiocayanates
B. Perchlorates
C. Propylthiouracil (Correct Answer)
D. Radioactive iodine

Explanation: **Explanation:** **Propylthiouracil (PTU)** is the drug of choice for thyroid storm because of its unique dual mechanism of action. Unlike other antithyroid drugs, PTU not only inhibits the enzyme **thyroid peroxidase** (preventing the synthesis of new thyroid hormones) but also **inhibits the peripheral conversion of T4 to the more potent T3** by blocking the 5’-deiodinase enzyme. In a life-threatening thyroid storm, rapidly reducing the peripheral levels of active T3 is crucial for clinical stabilization. **Why other options are incorrect:** * **Thiocyanates and Perchlorates (Options A & B):** These are ionic inhibitors that block the iodide trap. They are rarely used clinically due to toxicity (e.g., aplastic anemia with perchlorates) and are significantly less effective than thionamides in acute crises. * **Radioactive Iodine (Option D):** RAI is strictly contraindicated in thyroid storm. It causes radiation thyroiditis, which initially leads to the release of stored thyroid hormones into the blood, potentially worsening the storm. It is used for permanent ablation only after the patient is rendered euthyroid. **Clinical Pearls for NEET-PG:** * **Management Sequence:** The standard protocol for thyroid storm is: **PTU** (to stop synthesis/conversion) → **Iodides/Lugol’s Iodine** (to inhibit hormone release via the Wolff-Chaikoff effect, given 1 hour *after* PTU) → **Propranolol** (to control sympathetic overactivity) → **Hydrocortisone** (to prevent adrenal insufficiency and further inhibit T4 to T3 conversion). * **Pregnancy:** PTU is the drug of choice in the **1st trimester** (less teratogenic), while Methimazole is preferred in the 2nd and 3rd trimesters (lower risk of hepatotoxicity).

Question 92: Which of the following drugs is not hypoglycemic?

A. Ethosuximide (Correct Answer)
B. Tolbutamide
C. Glibenclamide
D. Chlorpropamide

Explanation: ### Explanation **1. Why Ethosuximide is the Correct Answer:** Ethosuximide is an **Antiepileptic drug**, not a glucose-lowering agent. Its mechanism of action involves the inhibition of **T-type calcium channels** in thalamic neurons. It is clinically used as the drug of choice for **Absence seizures (Petit mal)**. It has no effect on insulin secretion or peripheral glucose utilization, and therefore, it does not cause hypoglycemia. **2. Analysis of Incorrect Options (Hypoglycemic Agents):** Options B, C, and D are all members of the **Sulfonylurea** class of oral hypoglycemic agents. They work by closing ATP-sensitive $K^+$ channels in the pancreatic $\beta$-cells, leading to depolarization, calcium influx, and subsequent insulin release. * **Tolbutamide (Option B):** A first-generation sulfonylurea with a short duration of action. * **Glibenclamide (Option C):** Also known as Glyburide, it is a potent second-generation sulfonylurea. It carries a high risk of prolonged hypoglycemia, especially in the elderly. * **Chlorpropamide (Option D):** A long-acting first-generation sulfonylurea. It is notorious for causing disulfiram-like reactions with alcohol and SIADH (Syndrome of Inappropriate Antidiuretic Hormone). **3. NEET-PG High-Yield Pearls:** * **Sulfonylurea Side Effects:** The most common side effect is hypoglycemia; the most unique is weight gain. * **Chlorpropamide:** Remember the "C"s: **C**hlorpropamide causes **C**holestatic jaundice and **C**entral DI treatment (though it causes SIADH as a side effect). * **Ethosuximide Mnemonic:** "Ethosuximide **S**tops **S**pikes"—it is the first-line treatment for Absence seizures characterized by 3 Hz spike-and-wave discharges on EEG. Its main side effects are GI distress and fatigue (EFGH: **E**thosuximide, **F**atigue, **G**I distress, **H**eadache).

Question 93: Therapeutic uses of prostaglandin E1 include all of the following, except:

A. Medical termination of pregnancy
B. Impotence
C. Primary pulmonary hypertension (Correct Answer)
D. Maintenance of patent ductus arteriosus

Explanation: **Explanation:** The correct answer is **C. Primary pulmonary hypertension**. Prostaglandin E1 (PGE1), also known as **Alprostadil**, is a potent vasodilator and smooth muscle relaxant. However, it is not the drug of choice for primary pulmonary hypertension. The preferred prostaglandin analogs for pulmonary hypertension are **PGI2 (Prostacyclin) analogs**, such as **Epoprostenol, Treprostinil, and Iloprost**, which specifically target pulmonary vasculature. **Analysis of Options:** * **Medical Termination of Pregnancy (MTP):** **Misoprostol** is a synthetic PGE1 analog. It is used in combination with Mifepristone for MTP because it induces uterine contractions and cervical ripening. * **Impotence (Erectile Dysfunction):** Alprostadil (PGE1) can be administered via intracavernosal injection or intraurethral suppository. It works by relaxing the trabecular smooth muscle and dilating cavernosal arteries, increasing blood flow to the penis. * **Maintenance of Patent Ductus Arteriosus (PDA):** In neonates with cyanotic heart disease (e.g., Transposition of Great Arteries), PGE1 infusion is used to keep the ductus arteriosus open to maintain systemic or pulmonary blood flow until surgery. **NEET-PG High-Yield Pearls:** 1. **PGE1 (Alprostadil/Misoprostol):** Used for PDA maintenance, ED, and NSAID-induced peptic ulcers. 2. **PGE2 (Dinoprostone):** Primarily used for cervical ripening and induction of labor. 3. **PGF2α (Latanoprost/Carboprost):** Used for Glaucoma (Latanoprost) and Postpartum Hemorrhage (Carboprost). 4. **PGI2 (Epoprostenol):** Used for Pulmonary Hypertension and inhibiting platelet aggregation during hemodialysis. 5. **PDA Closure:** While PGE1 *maintains* PDA, **NSAIDs (Indomethacin or Ibuprofen)** are used to *close* a PDA by inhibiting prostaglandin synthesis.

Question 94: Continuous GnRH administration is useful in all the following conditions EXCEPT:

A. Precocious puberty
B. Prostate cancer
C. Male infertility (Correct Answer)
D. Endometriosis

Explanation: To answer this question, one must understand the "GnRH Paradox": the physiological effect of GnRH depends entirely on its mode of administration [1, 2]. ### 1. Why "Male Infertility" is the Correct Answer In male infertility (specifically hypogonadotropic hypogonadism), the goal is to stimulate the pituitary to release LH and FSH to induce spermatogenesis. This requires **pulsatile administration** of GnRH (mimicking physiological secretion) [1, 2]. **Continuous administration** of GnRH (or long-acting GnRH analogs like Leuprolide) causes **down-regulation and desensitization** of GnRH receptors on pituitary gonadotropes [1, 2]. This leads to a state of "medical castration" (suppression of LH/FSH and testosterone), which would worsen infertility. ### 2. Why the Other Options are Incorrect Continuous GnRH administration is used to suppress the Pituitary-Gonadal axis in hormone-dependent conditions: * **Precocious Puberty:** Suppression of premature LH/FSH release prevents early bone maturation and development of secondary sexual characteristics [2]. * **Prostate Cancer:** By suppressing LH, testosterone levels drop to castrate levels, inhibiting the growth of testosterone-dependent prostatic tumors [1]. * **Endometriosis:** Suppression of the axis leads to a hypoestrogenic state, which causes atrophy of ectopic endometrial tissue and provides symptomatic relief [1, 2]. ### 3. High-Yield Clinical Pearls for NEET-PG * **Pulsatile GnRH:** Used for **Infertility** (Male/Female) and Delayed Puberty [1, 2]. * **Continuous GnRH:** Used for **Prostate Cancer, Endometriosis, Precocious Puberty, and Uterine Fibroids [1, 2].** * **Flare Phenomenon:** Initial continuous administration causes a transient rise in LH/T before suppression occurs [1, 2]. To prevent this in prostate cancer, **Flutamide** (an androgen antagonist) is co-administered. * **Drugs:** Leuprolide, Goserelin, Nafarelin, and Buserelin are common GnRH analogs [1, 2].

Question 95: Misoprostol is an analogue of:

A. PGE1 (Correct Answer)
B. PGE2
C. PGF2
D. PGI2

Explanation: **Explanation:** **Misoprostol** is a synthetic methyl analogue of **Prostaglandin E1 (PGE1)**. It is primarily used in clinical practice for its cytoprotective effects on the gastric mucosa and its potent oxytocic properties. 1. **Why PGE1 is correct:** Misoprostol mimics the action of endogenous PGE1. In the stomach, it binds to EP3 receptors on parietal cells to inhibit gastric acid secretion and stimulates mucus and bicarbonate secretion. In the uterus, it causes cervical ripening and uterine contractions, making it vital for obstetric and gynecological procedures. 2. **Why other options are incorrect:** * **PGE2 (Dinoprostone):** While also used for cervical ripening, Misoprostol is specifically a PGE1 analogue. Dinoprostone is the naturally occurring PGE2. * **PGF2α (Carboprost/Dinoprost):** These are used to control postpartum hemorrhage (PPH) by causing strong uterine contractions but belong to the F-series of prostaglandins. * **PGI2 (Epoprostenol):** This is Prostacyclin, used primarily as a vasodilator and inhibitor of platelet aggregation in pulmonary arterial hypertension. **High-Yield Clinical Pearls for NEET-PG:** * **NSAID-induced Ulcers:** Misoprostol is the drug of choice for the *prevention* of NSAID-induced gastric ulcers (though PPIs are more commonly used due to better tolerability). * **Obstetric Uses:** Used for medical abortion (combined with Mifepristone), induction of labor, and management of Postpartum Hemorrhage (PPH). * **Side Effects:** The most common side effect is **diarrhea** and abdominal cramps. * **Contraindication:** It is strictly contraindicated in pregnancy unless used for legal termination, as it is highly **teratogenic** (associated with Moebius syndrome).

Question 96: Which of the following is NOT a pharmacological property of Repaglinide?

A. Insulin Secretagogues
B. Reduces insulin resistance (Correct Answer)
C. Causes less hypoglycemia than sulfonylureas
D. Effectively reduced postprandial hyperglycemia

Explanation: **Explanation:** **Repaglinide** belongs to the **Meglitinide (Glinide)** class of oral hypoglycemic agents. The correct answer is **B** because Repaglinide does not reduce insulin resistance; its primary action is to stimulate insulin secretion. 1. **Why Option B is correct:** Reducing insulin resistance is a characteristic of **Insulin Sensitizers** like Biguanides (Metformin) and Thiazolidinediones (Pioglitazone). Repaglinide has no direct effect on insulin receptors or glucose transporters in peripheral tissues. 2. **Why Option A is incorrect:** Repaglinide is an **Insulin Secretagogue**. Like sulfonylureas, it closes ATP-sensitive $K^+$ channels in pancreatic $\beta$-cells, leading to depolarization, $Ca^{2+}$ influx, and subsequent insulin release. 3. **Why Option C is incorrect:** Repaglinide has a very short half-life and a rapid onset/offset of action. Because its effect is transient and glucose-dependent, it causes **less incidence of late-fasting hypoglycemia** compared to long-acting sulfonylureas (e.g., Glibenclamide). 4. **Why Option D is incorrect:** Due to its rapid onset, it is specifically used as a **"Prandial Glucose Regulator."** It is taken just before meals to effectively control postprandial glycemic spikes. **High-Yield NEET-PG Pearls:** * **Mechanism:** Binds to a distinct site on the SUR1 receptor (different from the sulfonylurea binding site). * **Safe in Renal Impairment:** Repaglinide is primarily excreted via bile/feces, making it a preferred secretagogue in patients with **chronic kidney disease (CKD)**. * **Skip a Meal, Skip a Dose:** Patients are advised to omit the dose if they skip a meal to avoid hypoglycemia.

Question 97: Which of the following drugs used in osteoporosis acts by decreasing the resorption of bone as well as inducing new bone formation?

A. Teriparatide
B. Ibandronate
C. Strontium ranelate (Correct Answer)
D. Calcitonin

Explanation: **Explanation** The correct answer is **Strontium ranelate**. This drug is unique in its pharmacological profile because it possesses a **dual mechanism of action**, often referred to as a "dual-acting bone agent" (DABA). 1. **Mechanism of Correct Option:** Strontium ranelate acts by: * **Increasing bone formation:** It stimulates the proliferation of osteoblast precursors and increases collagen synthesis. * **Decreasing bone resorption:** It inhibits osteoclast differentiation and activity (by increasing Osteoprotegerin and decreasing RANKL expression). This "uncoupling" of bone remodeling—where formation is promoted while resorption is suppressed—distinguishes it from other agents. 2. **Analysis of Incorrect Options:** * **Teriparatide (A):** A recombinant PTH analog. It is primarily an **anabolic agent** (induces new bone formation) but does not decrease resorption; in fact, long-term use can slightly increase resorption markers. * **Ibandronate (B):** A Bisphosphonate. These are purely **antiresorptive agents**. they inhibit osteoclast-mediated bone resorption but do not induce new bone formation. * **Calcitonin (D):** A hormone that directly inhibits osteoclasts. It is a weak **antiresorptive agent** and has no anabolic (bone-forming) properties. **NEET-PG High-Yield Pearls:** * **Strontium ranelate Side Effects:** It is associated with an increased risk of **cardiovascular events** (MI) and **Venous Thromboembolism (VTE)**. It is now generally reserved for patients with severe osteoporosis who cannot use other treatments. * **DRESS Syndrome:** Strontium ranelate is a known cause of Drug Reaction with Eosinophilia and Systemic Symptoms. * **Teriparatide Limit:** Due to the theoretical risk of **Osteosarcoma**, its use is typically limited to a maximum of 24 months.

Question 98: Which of the following statements about romosozumab is FALSE?

A. Romosozumab is a monoclonal antibody against sclerostin. (Correct Answer)
B. It acts by inhibiting osteoclast differentiation and activity.
C. It acts by stimulating osteoblast formation and activity.
D. It is indicated in postmenopausal osteoporosis.

Explanation: **Explanation:** Romosozumab is a novel agent used in the management of severe osteoporosis. The correct answer is **A** because it accurately describes the drug's mechanism of action: it is a humanized monoclonal antibody that binds to and inhibits **sclerostin**. Sclerostin is a protein produced by osteocytes that normally inhibits bone formation (by antagonizing the Wnt signaling pathway) and increases bone resorption. By blocking sclerostin, Romosozumab exerts a unique **"dual effect"**: 1. **Anabolic effect:** It stimulates osteoblast activity, leading to new bone formation (Option C is true). 2. **Antiresorptive effect:** It decreases osteoclast activity and differentiation (Option B is true). **Analysis of Options:** * **Option A (Correct):** This is the defining characteristic of the drug. * **Option B & C (Incorrect as False statements):** These are true statements regarding its dual mechanism. Unlike traditional agents which are either purely antiresorptive (Bisphosphonates) or purely anabolic (Teriparatide), Romosozumab does both. * **Option D (Incorrect as False statement):** It is indeed FDA-approved for the treatment of **postmenopausal osteoporosis** in women at high risk of fracture. **High-Yield Clinical Pearls for NEET-PG:** * **Black Box Warning:** Romosozumab carries a warning for increased risk of **myocardial infarction, stroke, and cardiovascular death**. It should not be initiated in patients who have had an MI or stroke within the preceding year. * **Administration:** It is administered as a subcutaneous injection once a month for a limited duration of **12 months** (due to waning anabolic effects over time). * **Sequence:** After 12 months of Romosozumab, therapy should transition to an antiresorptive agent (like Alendronate) to maintain the bone density gains.

Question 99: Indications for the use of newer insulins include all of the following EXCEPT:

A. Insulin resistance
B. Lipodystrophy
C. Pregnancy
D. Diabetic kidney disease (Correct Answer)

Explanation: **Explanation:** The correct answer is **Diabetic Kidney Disease (DKD)**. **1. Why Diabetic Kidney Disease is the correct answer:** In patients with chronic kidney disease (CKD) or DKD, the renal clearance of insulin is significantly reduced, leading to a prolonged half-life and an increased risk of severe hypoglycemia. While newer insulin analogs (like Lispro or Glargine) can be used in DKD, they are **not specifically indicated** over conventional human insulins for this condition. In fact, as renal function declines, insulin doses often need to be *decreased* rather than switched to a newer analog. The primary management focus in DKD is dose titration, not the specific formulation of insulin. **2. Why the other options are incorrect:** * **Insulin Resistance:** Newer insulin analogs (especially concentrated forms like U-500) and specific structural modifications help overcome high dose requirements and improve absorption kinetics in resistant states. * **Lipodystrophy:** This is often an immunological or inflammatory reaction to older, less pure animal insulins. Highly purified newer recombinant human insulins and analogs have a significantly lower incidence of injection-site lipodystrophy. * **Pregnancy:** Rapid-acting analogs (Lispro, Aspart) and long-acting analogs (Detemir) are now frequently preferred in pregnancy (Category B) because they provide better postprandial glycemic control and lower risk of nocturnal hypoglycemia compared to NPH or Regular insulin. **Clinical Pearls for NEET-PG:** * **Drug of Choice:** Insulin remains the safest drug for diabetes in pregnancy and CKD, but dose adjustment is mandatory in CKD. * **Hypoglycemia Risk:** The main advantage of long-acting analogs (Glargine/Degludec) over NPH is the "peakless" profile, which significantly reduces nocturnal hypoglycemia. * **Ultra-rapid analogs:** Fiasp (Faster-acting Insulin Aspart) contains Vitamin B3 (Niacinamide) to increase the speed of absorption.

Question 100: All of the following statements regarding Octreotide are true, EXCEPT:

A. It is a somatostatin analogue
B. Used in secretory diarrhea in AIDS
C. Used in carcinoid
D. An absorbent (Correct Answer)

Explanation: **Explanation:** **Octreotide** is a synthetic long-acting octapeptide analogue of **Somatostatin** (Growth Hormone Inhibiting Hormone). It mimics the natural hormone but has a much longer half-life (approx. 1.5 hours vs. 2 minutes). **Why Option D is the Correct Answer (The False Statement):** Octreotide is **not an absorbent**. Absorbents (like Kaolin or Pectin) work locally in the gut lumen to bind toxins or water. Octreotide is a systemic pharmacological agent administered parenterally (SC/IV) that acts via specific somatostatin receptors (SSTR-2, 3, and 5) to inhibit the secretion of various hormones and intestinal fluids. **Analysis of Other Options:** * **Option A (True):** It is the most commonly used somatostatin analogue. It is preferred over natural somatostatin because it is more potent and has a longer duration of action. * **Option B (True):** It is highly effective in treating refractory **secretory diarrhea** associated with AIDS and chemotherapy because it decreases intestinal secretion and slows GI motility. * **Option C (True):** It is the drug of choice for symptomatic relief in **Carcinoid syndrome** (flushing and diarrhea) by inhibiting the release of serotonin and other peptides from the tumor. **NEET-PG High-Yield Pearls:** * **Clinical Uses:** Acromegaly (inhibits GH), Esophageal varices (causes splanchnic vasoconstriction), and VIPomas. * **Adverse Effects:** Most common side effect is **steatorrhea** (due to inhibition of pancreatic enzymes). Long-term use carries a high risk of **cholelithiasis** (gallstones) due to inhibition of gallbladder contractility and bile secretion. * **Diagnostic Use:** Radiolabeled octreotide (OctreoScan) is used for localizing neuroendocrine tumors.

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

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Androgens and Anabolic Steroids

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Hormonal Contraceptives

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Drugs Affecting Calcium Metabolism

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Drugs for Osteoporosis

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Pharmacological Management of Obesity

Practice Questions

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