Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 591: All are true regarding selective estrogen receptor downregulator (SERD), Fulvestrant, except?

A. Used for the treatment of advanced breast cancer.
B. Is a selective estrogen antagonist.
C. Is slower, short-acting, and less safe than SERMs. (Correct Answer)
D. Administered as a once-monthly intramuscular dose.

Explanation: **Explanation** **Fulvestrant** is a unique hormonal agent classified as a **Selective Estrogen Receptor Downregulator (SERD)** [1]. Unlike SERMs (e.g., Tamoxifen), which have agonist effects in some tissues and antagonist effects in others, Fulvestrant is a **pure estrogen antagonist** with no agonist activity [3]. **Why Option C is the correct (False) statement:** Fulvestrant is actually **longer-acting** and has a **better safety profile** compared to many SERMs. It has a long half-life (approx. 40 days), allowing for infrequent dosing [1]. Furthermore, because it lacks the partial agonist activity of Tamoxifen, it does **not** increase the risk of endometrial cancer or venous thromboembolism, making it safer in those specific regards [2]. **Analysis of other options:** * **Option A:** It is FDA-approved for the treatment of hormone receptor-positive (HR+) **advanced or metastatic breast cancer**, particularly in postmenopausal women who have progressed on other anti-estrogen therapies [3]. * **Option B:** It binds to estrogen receptors (ER) with high affinity, blocking estrogen binding and triggering the **degradation (downregulation)** of the receptor protein [1]. Thus, it acts as a pure antagonist. * **Option D:** Due to its pharmacokinetic profile, it is administered as a **500 mg intramuscular (IM) injection** once monthly (after an initial loading dose) [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** "Bind, Block, Degrade." It leads to a total reduction in the number of estrogen receptors in the cell [1]. * **Indication:** Second-line therapy for metastatic breast cancer after Tamoxifen or Aromatase Inhibitor failure [3]. * **Side Effects:** Most common are injection site pain, hot flashes, and nausea. * **Comparison:** Unlike Tamoxifen (SERM), Fulvestrant does **not** carry a risk of uterine (endometrial) hyperplasia [2].

Question 592: What is the most important side effect of insulin?

A. Hypoglycaemia (Correct Answer)
B. Lipodystrophy
C. Insulin resistance
D. Antibodies to insulin

Explanation: **Explanation:** **1. Why Hypoglycaemia is the Correct Answer:** Hypoglycaemia is the **most common and most serious** acute complication of insulin therapy. It occurs when there is an imbalance between insulin dosage, carbohydrate intake, and physical activity. In clinical practice, it is considered the "limiting factor" in achieving glycemic control because severe episodes can lead to seizures, coma, or irreversible brain damage. For NEET-PG, always prioritize life-threatening or most frequent clinical outcomes when asked for the "most important" side effect. **2. Analysis of Incorrect Options:** * **B. Lipodystrophy:** This refers to atrophy or hypertrophy of subcutaneous fat at the injection site. While common with older bovine/porcine insulins, its incidence has significantly decreased with the use of highly purified human recombinant insulins and frequent rotation of injection sites. * **C. Insulin Resistance:** This is a physiological state (often defined as requiring >200 units/day) rather than a direct side effect. It is usually secondary to obesity, infections, or anti-insulin antibodies, but it is not the primary adverse concern for most patients. * **D. Antibodies to Insulin:** While the body can produce IgG antibodies against exogenous insulin, this rarely leads to clinical issues with modern human insulin preparations. It was a much more significant concern with animal-derived insulins. **3. High-Yield Clinical Pearls for NEET-PG:** * **Whipple’s Triad:** Used to diagnose hypoglycaemia (Symptoms of low BG, low plasma glucose levels, and relief of symptoms when glucose is raised). * **Somogyi Effect:** Post-hypoglycaemic hyperglycemia caused by a counter-regulatory hormone surge (epinephrine, glucagon, cortisol) following an overdose of insulin at night. * **Weight Gain:** Aside from hypoglycaemia, weight gain is the most common metabolic side effect of insulin therapy. * **Treatment:** For conscious patients, use the "15-15 rule" (15g carbs, check in 15 mins); for unconscious patients, IV Dextrose (25-50%) or IM Glucagon is the treatment of choice.

Question 593: Growth Hormone may be beneficial in which of the following conditions, except?

A. In children with constitutional growth delay.
B. In treatment of osteoporosis.
C. Laron type dwarfism. (Correct Answer)
D. Panhypopituitarism.

Explanation: ### Explanation **1. Why Laron Type Dwarfism is the Correct Answer:** Laron dwarfism is characterized by **Growth Hormone (GH) receptor insensitivity**. In this condition, GH levels are actually normal or elevated, but the receptors are non-functional, leading to a failure in the production of **IGF-1 (Insulin-like Growth Factor-1)**. Since the defect lies at the receptor level, administering exogenous Growth Hormone will have no effect. The treatment of choice for Laron dwarfism is **Mecasermin** (recombinant IGF-1). **2. Analysis of Incorrect Options:** * **Constitutional Growth Delay:** GH can be used to increase final adult height in children who are significantly below the growth curve, even if they are not GH deficient. * **Osteoporosis:** GH stimulates osteoblast activity and increases bone mineral density. While not a first-line treatment, it is physiologically beneficial and approved for use in GH-deficient adults with low bone mass. * **Panhypopituitarism:** This involves a deficiency of all anterior pituitary hormones, including GH. Replacement therapy with recombinant GH (Somatropin) is a standard indication to restore normal growth and metabolic function. **3. High-Yield Clinical Pearls for NEET-PG:** * **Somatropin:** Recombinant human GH used for GH deficiency, Turner syndrome, Prader-Willi syndrome, and Chronic Renal Failure. * **Somatomedin C:** Another name for IGF-1; it mediates most of the growth-promoting effects of GH. * **Side Effects of GH:** Slipped capital femoral epiphysis, pseudotumor cerebri, and hyperglycemia (diabetogenic potential). * **Contraindication:** GH should not be used in patients with active malignancy or closed epiphyses.

Question 594: All of the following drugs can be used for diabetes insipidus, except:

A. Amiloride
B. Furosemide (Correct Answer)
C. Chlorpropamide
D. Carbamazepine

Explanation: **Explanation:** The correct answer is **Furosemide**. Furosemide is a loop diuretic that inhibits the Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending limb of the loop of Henle. This action abolishes the corticomedullary osmotic gradient, preventing the kidney from concentrating urine. Consequently, it causes **diuresis** (increased water loss), which would worsen the polyuria seen in Diabetes Insipidus (DI). **Why the other options are used in DI:** * **Amiloride (Option A):** This is the drug of choice for **Lithium-induced Nephrogenic DI**. It blocks the epithelial sodium channels (ENaC) in the collecting duct, preventing lithium from entering the cells and exerting its toxic effect. * **Chlorpropamide (Option C):** A first-generation sulfonylurea used in **Central DI**. It sensitizes the renal tubules to the action of ADH and may also stimulate the release of ADH from the hypothalamus. * **Carbamazepine (Option D):** Primarily an anticonvulsant, it is used in **Central DI** because it stimulates the release of endogenous ADH. **Clinical Pearls for NEET-PG:** 1. **Thiazide Diuretics:** Paradoxically used in Nephrogenic DI. They cause mild ECF volume depletion, leading to increased proximal tubular reabsorption of salt and water, which reduces the volume of filtrate reaching the distal nephron. 2. **Drug of Choice (DOC):** Desmopressin (dDAVP) is the DOC for Central DI. 3. **Indomethacin:** Sometimes used in Nephrogenic DI as it inhibits prostaglandins (which are natural ADH antagonists).

Question 595: All of the following are true regarding the use of iodine, except:

A. It inhibits the release of thyroid hormones.
B. It causes acute inhibition of iodotyrosine and iodothyronine synthesis.
C. It can cause iodism.
D. Its use is contraindicated in hyperthyroidism. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D**, as iodine is **not** contraindicated in hyperthyroidism; rather, it is used strategically in specific clinical scenarios. **1. Why Option D is the correct answer (The Exception):** Iodine (usually as Lugol’s iodine or potassium iodide) is a standard treatment for hyperthyroidism in two specific cases: **Pre-operative preparation** for thyroidectomy (to decrease the vascularity and size of the gland) and **Thyroid Storm** (to rapidly block hormone release). Therefore, stating it is contraindicated is medically incorrect. **2. Analysis of other options:** * **Option A (True):** High doses of iodine acutely inhibit the proteolysis of thyroglobulin, thereby blocking the **release** of T3 and T4 into the circulation. This is the fastest-acting mechanism to lower thyroid levels. * **Option B (True):** This refers to the **Wolff-Chaikoff effect**, where high plasma iodide concentrations cause a transient inhibition of the organic binding of iodine (organification), stopping the synthesis of iodotyrosine and iodothyronine. * **Option C (True):** **Iodism** is a chronic toxicity resulting from iodine use. Symptoms include a metallic taste, burning sensation in the mouth, sneezing (coryza), and swelling of the eyelids/salivary glands. **Clinical Pearls for NEET-PG:** * **The Escape Phenomenon:** The Wolff-Chaikoff effect is transient; the thyroid "escapes" this inhibition after 10–14 days. Thus, iodine should not be used as long-term monotherapy. * **Jod-Basedow Phenomenon:** In contrast to the Wolff-Chaikoff effect, iodine administration in a deficient patient can sometimes *induce* hyperthyroidism. * **Amiodarone:** This antiarrhythmic drug contains high iodine content and can cause both hyper- and hypothyroidism.

Question 596: Flushing is common in patients taking which of the following oral hypoglycemic drugs with alcohol?

A. Chlorpropamide (Correct Answer)
B. Phenformin
C. Glibenclamide
D. Tolazamide

Explanation: ### Explanation **1. Why Chlorpropamide is Correct:** Chlorpropamide is a first-generation sulfonylurea known for causing a **Disulfiram-like reaction** when consumed with alcohol. This occurs because chlorpropamide inhibits the enzyme **aldehyde dehydrogenase**, leading to the accumulation of acetaldehyde in the blood. High levels of acetaldehyde trigger systemic vasodilation, resulting in symptoms such as intense flushing (especially of the face), nausea, tachycardia, and headache. This specific phenomenon is often referred to as **Chlorpropamide-Alcohol Flush (CPAF)**. **2. Why the Other Options are Incorrect:** * **Phenformin (B):** This is a biguanide (like metformin) that was withdrawn from the market primarily due to a high risk of **lactic acidosis**. While it interacts with alcohol to increase lactic acid levels, it does not typically cause a disulfiram-like flushing reaction. * **Glibenclamide (C) & Tolazamide (D):** These are second-generation and first-generation sulfonylureas, respectively. While all sulfonylureas can theoretically cause mild disulfiram-like reactions, the incidence is significantly lower than with chlorpropamide. Glibenclamide, in particular, has a very low propensity for this side effect. **3. High-Yield Clinical Pearls for NEET-PG:** * **Chlorpropamide** has the longest half-life among sulfonylureas (~36 hours) and is most likely to cause **SIADH** (dilutional hyponatremia) and prolonged hypoglycemia. * **Other drugs causing Disulfiram-like reactions:** Metronidazole (most common), Tinidazole, Griseofulvin, Cefotetan, and Procarbazine. * **Management:** The reaction is self-limiting; the primary management is avoidance of alcohol while on these medications.

Question 597: Which dopamine agonist is used in the management of diabetes mellitus?

A. Metformin
B. Bromocriptine (Correct Answer)
C. Cabergoline
D. Vanadium salts

Explanation: **Explanation:** **Bromocriptine** is a potent dopamine D2 receptor agonist. While primarily known for treating hyperprolactinemia and Parkinson’s disease, a specific quick-release (QR) formulation of Bromocriptine is FDA-approved for the management of **Type 2 Diabetes Mellitus**. **Mechanism of Action:** In patients with Type 2 DM, there is often a decrease in dopaminergic tone in the hypothalamus during the morning. Bromocriptine QR, when administered within two hours of waking, acts on the circadian rhythm to increase hypothalamic dopaminergic activity. This results in a reduction of sympathetic outflow, leading to decreased hepatic glucose production (gluconeogenesis), reduced insulin resistance, and lower free fatty acid levels without increasing insulin secretion. **Analysis of Incorrect Options:** * **A. Metformin:** This is a Biguanide, not a dopamine agonist. It is the first-line drug for Type 2 DM, acting primarily by activating AMPK to inhibit hepatic gluconeogenesis. * **C. Cabergoline:** Although it is a long-acting dopamine agonist used for prolactinomas, it is **not** approved or used for the management of glycemic control in diabetes. * **D. Vanadium salts:** These are trace elements that have "insulin-mimetic" properties but are not dopamine agonists and are not used in standard clinical practice due to toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Bromocriptine QR** is the only dopamine agonist approved for DM. * It does **not** cause hypoglycemia or weight gain, making it unique among many oral hypoglycemics. * It is also known to reduce the risk of major adverse cardiovascular events (MACE). * **Side effects:** Nausea, dizziness, and orthostatic hypotension are common during initiation.

Question 598: Which drug acts on V2 receptors and is used in diabetes insipidus?

A. Telypressin
B. Vasopressin
C. Desmopressin (Correct Answer)
D. Pralispressin

Explanation: **Explanation:** **Desmopressin (dDAVP)** is a synthetic analog of Arginine Vasopressin (AVP). It is the drug of choice for **Central Diabetes Insipidus** due to its high selectivity for **V2 receptors** located in the collecting ducts of the kidney. Activation of V2 receptors increases water permeability by facilitating the insertion of aquaporin-2 channels, thereby reducing urine volume. **Why Desmopressin is preferred:** * **High V2 Selectivity:** It has a V2:V1 selectivity ratio of approximately 2000:1, meaning it provides potent antidiuretic effects without the significant vasoconstriction (V1-mediated) seen with natural vasopressin. * **Longer Duration:** It is more resistant to degradation by peptidases, offering a longer half-life (6–20 hours). **Analysis of Incorrect Options:** * **A. Terlipressin:** A prodrug of lysine-vasopressin with high **V1 selectivity**. It is primarily used in the management of bleeding esophageal varices and hepatorenal syndrome. * **B. Vasopressin:** The naturally occurring hormone (ADH). It acts non-selectively on V1 (vasoconstriction), V2 (antidiuresis), and V3 (ACTH release) receptors. Its short half-life and side effects (hypertension, abdominal cramps) make it less ideal for chronic DI management. * **D. Pralispressin:** This is a less commonly used analog; the standard clinical options for V2-related therapy remain Desmopressin. **NEET-PG High-Yield Pearls:** 1. **Route of Administration:** Desmopressin can be given intranasally, orally, or parenterally. Note that the oral dose is much higher due to low bioavailability. 2. **Other Uses of Desmopressin:** It increases the release of **Factor VIII and von Willebrand Factor (vWF)** from endothelial storage (Weibel-Palade bodies), making it useful in **Type I vWD** and **Mild Hemophilia A**. 3. **Nocturnal Enuresis:** Desmopressin is also used for bed-wetting in children. 4. **Adverse Effect:** The most serious side effect is **hyponatremia** (water intoxication).

Question 599: Which of the following is an anti-progesterone drug?

A. Cyproterone
B. Mifepristone (Correct Answer)
C. Spironolactone
D. Tamoxifen

Explanation: **Explanation:** **Mifepristone (RU-486)** is the correct answer because it is a potent **competitive progesterone receptor antagonist**. It binds to progesterone receptors with higher affinity than endogenous progesterone, preventing the hormone from maintaining the decidua. This leads to the detachment of the blastocyst and sensitization of the uterus to prostaglandins. **Analysis of Incorrect Options:** * **Cyproterone:** This is an **anti-androgen** (androgen receptor antagonist) with weak progestational activity. It is used in the management of hirsutism, acne, and precocious puberty. * **Spironolactone:** Primarily a potassium-sparing diuretic, it also acts as an **aldosterone antagonist** and has significant anti-androgenic properties. It is not an anti-progestin. * **Tamoxifen:** This is a **Selective Estrogen Receptor Modulator (SERM)**. It acts as an antagonist in the breast (used in breast cancer) but as an agonist in the bone and endometrium. **High-Yield Clinical Pearls for NEET-PG:** * **Medical Abortion Regimen:** Mifepristone (200 mg orally) is followed 36–48 hours later by **Misoprostol** (400–800 mcg) to induce uterine contractions. This is effective up to 7-9 weeks of gestation. * **Cushing’s Syndrome:** Mifepristone is also FDA-approved for controlling hyperglycemia in patients with endogenous Cushing’s syndrome (due to its **glucocorticoid receptor antagonism** at high doses). * **Emergency Contraception:** Mifepristone can be used as a single dose for emergency contraception (though Levonorgestrel and Ulipristal are more common). * **Ulipristal:** Another important Selective Progesterone Receptor Modulator (SPRM) used for emergency contraception and uterine fibroids.

Question 600: Which of the following statements regarding finasteride is FALSE?

A. It is used in the treatment of benign prostatic hyperplasia.
B. Impotence is well-documented after its use.
C. It blocks the conversion of testosterone to dihydrotestosterone. (Correct Answer)
D. It is a 5-alpha reductase inhibitor.

Explanation: **Explanation**The question asks for the **FALSE** statement regarding Finasteride. While Finasteride is indeed a 5-alpha reductase inhibitor, the phrasing of Option C is technically incorrect in a competitive exam context because it is **incomplete**.**1. Why Option C is the "False" Statement (The Correct Answer)**Finasteride is a **selective inhibitor of Type II 5-alpha reductase** [1]. In the human body, there are two isoenzymes: Type I (found mainly in the skin/liver) and Type II (found predominantly in the prostate and hair follicles) [1]. Finasteride specifically blocks the Type II isoenzyme [1]. A drug like **Dutasteride** is a non-selective inhibitor that blocks both Type I and Type II. In high-stakes exams like NEET-PG, "selective" vs. "non-selective" is a common point of distinction.**2. Analysis of Other Options*** **Option A:** Correct. By reducing Dihydrotestosterone (DHT) levels [1], Finasteride decreases prostate volume, improving urinary flow in **Benign Prostatic Hyperplasia (BPH)**.* **Option B:** Correct. Sexual dysfunction, including **impotence (erectile dysfunction)** and decreased libido, is a well-documented side effect in approximately 3-8% of patients.* **Option D:** Correct. Finasteride’s primary mechanism of action is the inhibition of the 5-alpha reductase enzyme [1].**High-Yield Clinical Pearls for NEET-PG:*** **Indications:** BPH (5 mg dose) and Male Pattern Baldness/Androgenetic Alopecia (1 mg dose) [1].* **Mechanism:** It prevents the conversion of Testosterone to the more potent **Dihydrotestosterone (DHT)** [1].* **Teratogenicity:** It is contraindicated in pregnancy (Category X) as it can cause feminization of a male fetus; pregnant women should not even handle crushed tablets [1].* **PSA Levels:** Finasteride can decrease PSA levels by approximately 50%; this must be accounted for when screening for prostate cancer.

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

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