Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 541: A vasopressin analogue does not produce therapeutic effect through vasopressin V2 receptor in which of the following conditions?

A. Central diabetes insipidus
B. Bleeding oesophageal varices (Correct Answer)
C. Type I von Willebrand's disease
D. Primary nocturnal enuresis

Explanation: **Explanation:** The therapeutic effect of vasopressin analogues depends on which receptor subtype is activated: **V1 receptors** (located on vascular smooth muscle, causing vasoconstriction) or **V2 receptors** (located in renal collecting ducts for water reabsorption and on vascular endothelium to release clotting factors). **Why Option B is Correct:** In **Bleeding Oesophageal Varices**, the goal is to reduce portal venous pressure. Drugs like **Terlipressin** (a vasopressin analogue) act primarily via **V1 receptors** to cause potent splanchnic vasoconstriction. This reduces blood flow into the portal system, thereby controlling the variceal bleed. It does not rely on V2 receptor activation for this therapeutic effect. **Why Other Options are Incorrect:** * **Central Diabetes Insipidus (A):** Desmopressin acts on **V2 receptors** in the renal collecting ducts to increase water permeability (via Aquaporin-2 channels), correcting the polyuria. * **Type I von Willebrand’s Disease (C):** Desmopressin stimulates **V2 receptors** on vascular endothelial cells, triggering the release of stored von Willebrand factor (vWF) and Factor VIII. * **Primary Nocturnal Enuresis (D):** Desmopressin acts on renal **V2 receptors** to increase urine concentration and decrease total urine volume produced overnight. **High-Yield Clinical Pearls for NEET-PG:** * **Desmopressin (dDAVP):** A selective **V2 agonist**. It is the drug of choice for Central DI and Nocturnal Enuresis because it lacks the V1-mediated pressor side effects. * **Terlipressin:** Preferred in variceal bleeding due to its long half-life and **V1 selectivity**. * **V3 Receptors:** Located in the anterior pituitary; they mediate the release of ACTH. * **SIADH Treatment:** Managed with "Vaptans" (e.g., Tolvaptan, Conivaptan), which are **V2 receptor antagonists**.

Question 542: Gynaecomastia is a side effect of all the following drugs EXCEPT:

A. Ranitidine (Correct Answer)
B. Cimetidine
C. Spironolactone
D. Ketoconazole

Explanation: **Explanation:** Gynaecomastia (enlargement of male breast tissue) occurs due to an imbalance between estrogenic and androgenic effects. This can be caused by drugs that increase estrogen levels, decrease testosterone synthesis, or block androgen receptors. **Why Ranitidine is the Correct Answer:** While **Cimetidine** is a notorious cause of gynaecomastia, **Ranitidine** (and other newer H2 blockers like Famotidine) does not share this side effect. Cimetidine has a unique imidazole ring structure that allows it to bind to androgen receptors and inhibit the metabolism of estradiol. Ranitidine lacks this structural affinity for androgen receptors and does not inhibit cytochrome P450 enzymes to the same extent, making it "endocrine-neutral." **Analysis of Incorrect Options:** * **Cimetidine:** A potent H2 receptor antagonist that acts as a weak anti-androgen and increases serum prolactin levels. It is a classic cause of gynaecomastia and erectile dysfunction. * **Spironolactone:** A potassium-sparing diuretic that acts as an androgen receptor antagonist and inhibits testosterone synthesis. It is the most common drug-induced cause of gynaecomastia. * **Ketoconazole:** An antifungal that inhibits the enzyme **17,20-lyase** (part of the CYP450 system), leading to decreased synthesis of testosterone and cortisol. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Gynaecomastia ("DISCO"):** **D**igoxin, **I**soniazid, **S**pironolactone, **C**imetidine, **O**estrogens/Ketoconazole. * **Finasteride** (5-alpha reductase inhibitor) and **Flutamide** (androgen receptor blocker) are also high-yield causes. * Among H2 blockers, only Cimetidine is associated with significant anti-androgenic side effects.

Question 543: All of the following DPP-4 inhibitors should be used cautiously in renal insufficiency except?

A. Sitagliptin
B. Vildagliptin
C. Linagliptin (Correct Answer)
D. Saxagliptin

Explanation: **Explanation:** The correct answer is **Linagliptin**. **1. Why Linagliptin is the correct answer:** Most Dipeptidyl Peptidase-4 (DPP-4) inhibitors are primarily excreted via the kidneys. However, **Linagliptin** is unique because it is primarily excreted through the **enterohepatic route (bile/feces)**, with less than 5% eliminated renally. Consequently, it is the only DPP-4 inhibitor that requires **no dose adjustment** across all stages of renal insufficiency, making it the safest choice for patients with Chronic Kidney Disease (CKD). **2. Why the other options are incorrect:** * **Sitagliptin, Vildagliptin, and Saxagliptin:** These drugs are predominantly cleared by the kidneys. In patients with moderate to severe renal impairment, their plasma concentrations increase significantly, leading to a higher risk of adverse effects. Therefore, their doses must be reduced (e.g., Sitagliptin dose is halved if CrCl is 30–45 mL/min) or used with extreme caution. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Linagliptin:** Remember "**L**inagliptin leaves via the **L**iver" (Biliary excretion). * **Saxagliptin Alert:** It is specifically associated with an increased risk of hospitalization for **heart failure** (SAVOR-TIMI 53 trial). * **Vildagliptin:** It is the only DPP-4 inhibitor usually prescribed as a **twice-daily** dose (others are once daily) and requires monitoring of Liver Function Tests (LFTs). * **Weight Neutrality:** All DPP-4 inhibitors are weight-neutral and carry a low risk of hypoglycemia when used as monotherapy.

Question 544: Long-term ingestion of steroids leads to all of the following except?

A. Avascular necrosis of the head of the femur
B. Cataract
C. Glaucoma (Correct Answer)
D. Growth retardation

Explanation: **Explanation:** The correct answer is **C. Glaucoma**. This is a "trick" question common in NEET-PG, as it hinges on the distinction between **long-term systemic ingestion** versus **topical/local** administration of steroids. 1. **Why Glaucoma is the correct answer:** While steroids *can* cause glaucoma, it is primarily associated with **topical ophthalmic use** (eye drops) or periocular injections. Systemic (oral/IV) steroids are much more likely to cause cataracts than glaucoma. In the context of "long-term ingestion" (systemic route), glaucoma is the least common complication among the choices provided. 2. **Analysis of Incorrect Options:** * **Avascular Necrosis (AVN):** This is a classic, serious complication of long-term systemic steroid use. It most commonly affects the femoral head due to fat emboli or increased intraosseous pressure. * **Cataract:** Systemic steroids are a well-known cause of **Posterior Subcapsular Cataracts (PSC)**. This is a dose- and duration-dependent side effect. * **Growth Retardation:** In pediatric patients, chronic steroid use inhibits growth hormone (GH) secretion and has direct inhibitory effects on the epiphyseal plates, leading to stunted linear growth. **High-Yield Clinical Pearls for NEET-PG:** * **Cataract vs. Glaucoma:** Systemic steroids → Cataract (PSC); Topical steroids → Glaucoma. * **Withdrawal:** Long-term use (>2 weeks) requires tapering to prevent **Acute Adrenal Insufficiency** (due to HPA axis suppression). * **Metabolic Effects:** Steroids cause hyperglycemia (steroid-induced diabetes), osteoporosis, and centripetal obesity (Cushingoid features). * **Psychiatric:** "Steroid psychosis" can occur even with short-term high doses.

Question 545: Which of the following is a known side effect of Bromocriptine when used for lactation suppression?

A. It can cause deep vein thrombosis.
B. It can cause hypotension. (Correct Answer)
C. Metoclopramide potentiates the action of Bromocriptine.
D. It is given for 1 week only.

Explanation: **Explanation:** **Bromocriptine** is a semi-synthetic ergot alkaloid that acts as a potent **D2 receptor agonist** [4]. In the pituitary, it inhibits the release of prolactin, making it effective for treating hyperprolactinemia and, historically, for lactation suppression [1]. **Why Option B is Correct:** Bromocriptine causes **hypotension** (specifically postural/orthostatic hypotension) due to its central effect on the vasomotor center and its peripheral vasodilatory action via dopamine receptors. In the context of postpartum lactation suppression, this risk is significant, as it has been associated with rare but severe cardiovascular events like myocardial infarction and stroke, leading to its decline in use for this specific indication [2]. **Analysis of Incorrect Options:** * **Option A:** Bromocriptine does not cause DVT. In fact, ergot derivatives are more commonly associated with vasoconstriction and, in chronic cases, retroperitoneal or pulmonary fibrosis. * **Option C:** Metoclopramide is a **D2 receptor antagonist**. Therefore, it would **antagonize** (block) the effects of Bromocriptine, not potentiate them. * **Option D:** When used for lactation suppression, Bromocriptine must be administered for **2 weeks**. If stopped after only 1 week, "rebound lactation" often occurs because prolactin levels rise again [1]. **High-Yield NEET-PG Pearls:** * **Drug of Choice (DOC):** For both lactation suppression and prolactinomas, **Cabergoline** is now preferred over Bromocriptine due to its higher efficacy, longer half-life (twice-weekly dosing), and better side-effect profile [3]. * **Other Uses:** Bromocriptine is also used in **Parkinson’s disease** and **Acromegaly** (though it is less effective than Octreotide) [3]. * **Key Side Effects:** Nausea/vomiting (due to CTZ stimulation), digital vasospasm, and hallucinations [2].

Question 546: Steroids cause all of the following except:

A. Decreased healing of the wound
B. Water retention
C. Decreased bone matrix formation (Correct Answer)
D. None of the above

Explanation: This question is a classic "except" type question that tests your understanding of the physiological and pathological effects of glucocorticoids. ### **Explanation of the Correct Answer** The correct answer is **D (None of the above)**. *Note: In the provided prompt, Option C was marked as correct, but physiologically, steroids **do** cause decreased bone matrix formation. Therefore, since A, B, and C are all known side effects of steroids, the only logical answer to an "except" question is "None of the above."* **Mechanism of Bone Effects (Option C):** Glucocorticoids decrease bone matrix formation by inhibiting **osteoblast** activity and decreasing the synthesis of Type I collagen. They also increase bone resorption by stimulating **osteoclasts** and decreasing intestinal calcium absorption, leading to secondary hyperparathyroidism. ### **Analysis of Other Options** * **A. Decreased healing of the wound:** Steroids inhibit fibroblast proliferation and collagen synthesis. They also suppress the inflammatory response required for the initial stages of healing, leading to delayed wound closure and increased risk of dehiscence. * **B. Water retention:** Most glucocorticoids (especially Hydrocortisone and Prednisolone) possess some degree of **mineralocorticoid activity**. They act on the distal tubules to promote sodium and water reabsorption and potassium excretion. ### **High-Yield Clinical Pearls for NEET-PG** * **Steroid-Induced Osteoporosis:** This is the most common cause of drug-induced osteoporosis. The most common site of fracture is the **vertebrae**. * **Metabolic Effects:** Steroids cause hyperglycemia (via gluconeogenesis), "Buffalo hump" and "Moon facies" (due to fat redistribution), and muscle wasting (proteolysis). * **Hematological Effects:** Steroids cause **lymphopenia** and eosinopenia but lead to **neutrophilia** (due to decreased margination of neutrophils). * **Ocular Side Effects:** Chronic use is associated with **Glaucoma** (increased intraocular pressure) and **Posterior Subcapsular Cataracts**.

Question 547: Long term administration of glucocorticoids can cause all of the following except?

A. Proximal myopathy
B. Hyperkalemia (Correct Answer)
C. Hypertension
D. Cataract

Explanation: **Explanation:** The correct answer is **Hyperkalemia** because glucocorticoids actually cause **hypokalemia**, not hyperkalemia. **1. Why Hyperkalemia is the correct answer (The Exception):** Glucocorticoids (like Prednisolone or Dexamethasone) possess varying degrees of mineralocorticoid activity. They act on the distal renal tubules to promote the reabsorption of sodium and water in exchange for the excretion of potassium ($K^+$) and hydrogen ions ($H^+$). This physiological process leads to **hypokalemia** and metabolic alkalosis. Therefore, hyperkalemia is not a side effect of glucocorticoid therapy. **2. Why the other options are incorrect (Side effects of long-term use):** * **Proximal Myopathy (A):** Glucocorticoids are catabolic. They cause muscle protein breakdown and inhibit glucose uptake in muscles, leading to "steroid myopathy," typically affecting the proximal muscles of the limbs. * **Hypertension (C):** This occurs due to two mechanisms: the mineralocorticoid effect causing sodium/water retention and the enhancement of vascular reactivity to circulating catecholamines. * **Cataract (D):** Long-term use is a well-known risk factor for **posterior subcapsular cataracts**. It also increases intraocular pressure, potentially leading to glaucoma. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Steroid Side Effects:** "CUSHINGOID" (Cataracts, Ulcers, Skin thinning, Hypertension/Hirsutism, Immunosuppression, Necrosis of femoral head, Glucose elevation, Osteoporosis, Impaired wound healing, Depression/Psychosis). * **Osteoporosis:** Glucocorticoids are the most common cause of drug-induced osteoporosis (they inhibit osteoblasts and decrease calcium absorption). * **Growth:** In children, they cause growth retardation by inhibiting GH secretion and affecting the epiphyseal plates.

Question 548: Which of the following statements is TRUE about Clomiphene?

A. Anti-gonadotrophin
B. Anti-progesterone
C. Anti-oestrogen (Correct Answer)
D. Anti-androgenic

Explanation: **Explanation:** **Clomiphene citrate** is a **Selective Oestrogen Receptor Modulator (SERM)**. Its primary mechanism of action involves binding to oestrogen receptors in the **hypothalamus** and **anterior pituitary**. 1. **Why Option C is Correct:** Clomiphene acts as a **competitive antagonist (anti-oestrogen)** at the hypothalamic level. By blocking the negative feedback inhibition normally exerted by endogenous oestrogen, it tricks the brain into perceiving low oestrogen levels. This leads to an increased secretion of **GnRH**, which subsequently increases the pulsatile release of **FSH and LH** from the pituitary. The rise in FSH stimulates follicular growth, making it the **first-line drug for ovulation induction** in patients with Polycystic Ovary Syndrome (PCOS). 2. **Why Other Options are Incorrect:** * **A (Anti-gonadotrophin):** Incorrect. Clomiphene is actually a **pro-gonadotrophin** because it increases the levels of FSH and LH. * **B (Anti-progesterone):** Incorrect. Drugs like **Mifepristone** are anti-progesterones. Clomiphene has no significant effect on progesterone receptors. * **D (Anti-androgenic):** Incorrect. Drugs like **Spironolactone, Cyproterone, or Flutamide** are anti-androgens. **High-Yield Clinical Pearls for NEET-PG:** * **Indication:** Drug of choice for infertility due to anovulation (PCOS). * **Side Effects:** Multiple pregnancies (mostly twins), ovarian hyperstimulation syndrome (OHSS), and vasomotor flushes (hot flashes). * **Contraindications:** Liver disease and ovarian cysts (not due to PCOS). * **Note:** While it is an antagonist in the hypothalamus, it acts as a weak partial agonist in the ovaries.

Question 549: Which of the following drugs is an aromatase inhibitor?

A. Raloxifine
B. Tamoxifen
C. Leuprolide
D. Letrozole (Correct Answer)

Explanation: **Explanation:** **Correct Answer: D. Letrozole** **Mechanism of Action:** Aromatase is the enzyme responsible for the final rate-limiting step in estrogen synthesis—the conversion of androgens (androstenedione and testosterone) into estrogens (estrone and estradiol). **Letrozole** is a potent, non-steroidal, competitive **aromatase inhibitor**. By blocking this enzyme, it significantly lowers circulating estrogen levels. It is primarily used in the treatment of hormone-responsive breast cancer in postmenopausal women and for ovulation induction in infertility. **Analysis of Incorrect Options:** * **A & B (Raloxifene and Tamoxifen):** These are **SERMs (Selective Estrogen Receptor Modulators)**. They do not inhibit estrogen production; instead, they bind to estrogen receptors and act as either agonists or antagonists depending on the tissue. Tamoxifen is an antagonist in the breast but an agonist in the endometrium, while Raloxifene is an antagonist in both the breast and endometrium. * **C (Leuprolide):** This is a **GnRH analogue**. Continuous administration causes downregulation of GnRH receptors in the pituitary, leading to decreased FSH and LH, which ultimately suppresses ovarian/testicular steroidogenesis. **NEET-PG High-Yield Pearls:** * **Classification of Aromatase Inhibitors:** * **Type I (Irreversible/Steroidal):** Exemestane, Formestane. * **Type II (Reversible/Non-steroidal):** Letrozole, Anastrozole. * **Clinical Use:** Letrozole is now often preferred over Clomiphene citrate for **ovulation induction** in PCOS due to higher live birth rates and a better side effect profile (less thinning of the endometrium). * **Side Effects:** Unlike SERMs, aromatase inhibitors increase the risk of **osteoporosis** and fractures due to profound estrogen deprivation.

Question 550: L-Thyroxine is used in which of the following conditions?

A. Thyroid storm
B. Cretinism (Correct Answer)
C. Endemic goiter
D. Graves' disease

Explanation: **Explanation:** **L-Thyroxine (T4)** is the synthetic form of the thyroid hormone thyroxine. It is the drug of choice for hormone replacement therapy in all forms of hypothyroidism. **1. Why Cretinism is Correct:** Cretinism refers to **congenital hypothyroidism**, a condition where there is a severe deficiency of thyroid hormones from birth. Thyroid hormones are critical for brain development and skeletal growth. Immediate and lifelong replacement with L-Thyroxine is mandatory to prevent irreversible intellectual disability and growth retardation. T4 is preferred over T3 because of its longer half-life (7 days), consistent blood levels, and peripheral conversion to T3 as needed by tissues. **2. Why Other Options are Incorrect:** * **Thyroid Storm:** This is a life-threatening state of hyperthyroidism. Treatment involves **anti-thyroid drugs** (Propylthiouracil/Methimazole), beta-blockers, and iodine, not more thyroid hormone. * **Endemic Goiter:** This is usually caused by **iodine deficiency**. While T4 can shrink a goiter by suppressing TSH, the primary treatment and prevention strategy is iodine supplementation (e.g., iodized salt). * **Graves' Disease:** This is an autoimmune condition causing **hyperthyroidism**. It is treated with anti-thyroid drugs, radioactive iodine, or surgery—never L-Thyroxine (unless a "block and replace" regimen is used, which is not the primary indication). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** L-Thyroxine is the DOC for Myxedema coma (given IV) and Hashimoto’s thyroiditis. * **Administration:** It should be taken on an **empty stomach** (30-60 minutes before breakfast) as food, calcium, and iron supplements interfere with its absorption. * **Monitoring:** The best parameter to monitor the efficacy of L-Thyroxine therapy in primary hypothyroidism is the **Serum TSH level**. * **Pregnancy:** Requirements for L-Thyroxine typically **increase** during pregnancy.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

Insulin and Oral Hypoglycemic Agents

Practice Questions

Adrenocorticosteroids

Practice Questions

Sex Hormones: Estrogens and Progestins

Practice Questions

Androgens and Anabolic Steroids

Practice Questions

Hormonal Contraceptives

Practice Questions

Drugs Affecting Calcium Metabolism

Practice Questions

Drugs for Osteoporosis

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Pharmacological Management of Obesity

Practice Questions

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