Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 621: Which drug inhibits uterine contractility and can cause pulmonary edema?

A. Ritodrine (Correct Answer)
B. Nifedipine
C. Indomethacin
D. Atosiban

Explanation: The correct answer is **Ritodrine**. **Mechanism and Rationale:** Ritodrine is a **selective $\beta_2$-adrenergic agonist** used as a tocolytic to delay preterm labor. It works by increasing intracellular cAMP, which leads to the relaxation of uterine smooth muscle (inhibiting contractility). However, $\beta_2$ agonists have significant systemic side effects. The most serious complication is **pulmonary edema**, which occurs due to a combination of fluid retention (via $\beta_1$ cross-reactivity and ADH release), tachycardia, and increased capillary permeability. **Analysis of Incorrect Options:** * **Nifedipine:** A Calcium Channel Blocker (CCB). While it is currently the first-line tocolytic due to its better safety profile, its primary side effects are hypotension, flushing, and headache, rather than pulmonary edema [1]. * **Indomethacin:** A COX inhibitor (NSAID) used as a tocolytic. Its major risks are fetal, specifically the **premature closure of the ductus arteriosus** and oligohydramnios. * **Atosiban:** A competitive antagonist of **oxytocin receptors**. It is highly specific for the uterus and has the fewest maternal side effects among all tocolytics, making it an unlikely cause of pulmonary edema [1]. **High-Yield NEET-PG Pearls:** * **Drug of Choice (DOC):** Nifedipine is now preferred over Ritodrine for tocolysis due to the latter's cardiovascular risks [1]. * **Metabolic Side Effects of $\beta_2$ Agonists:** Hyperglycemia, hypokalemia (due to potassium shifting into cells), and tachycardia. * **Contraindication:** Ritodrine should be avoided in patients with pre-existing cardiac disease or uncontrolled diabetes.

Question 622: Which one of the following drugs is NOT a uterine relaxant?

A. Isoxsuprine
B. Dopamine (Correct Answer)
C. Salbutamol
D. Terbutaline

Explanation: **Explanation:** Uterine relaxants, also known as **Tocolytics**, are drugs used to delay preterm labor by inhibiting uterine contractions. The physiological basis for uterine relaxation primarily involves the stimulation of **$\beta_2$-adrenergic receptors** located on the myometrium. **Why Dopamine is the correct answer:** Dopamine is a catecholamine that acts predominantly on dopaminergic ($D_1, D_2$) and adrenergic ($\alpha_1, \beta_1$) receptors. It does **not** have a significant effect on $\beta_2$-receptors in the uterus. Its primary clinical uses are in the management of cardiogenic shock and hemodynamic instability, where it increases cardiac output and maintains renal perfusion. It has no role as a tocolytic. **Analysis of Incorrect Options:** * **Isoxsuprine:** A traditional $\beta$-receptor agonist formerly widely used as a uterine relaxant and peripheral vasodilator. * **Salbutamol & Terbutaline:** These are selective **$\beta_2$-agonists**. While commonly known as bronchodilators, they also relax the myometrium by increasing intracellular cAMP, which leads to a decrease in calcium levels and inhibition of myosin light chain kinase. Terbutaline is frequently used off-label to arrest preterm labor. **NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC):** Currently, **Atosiban** (Oxytocin antagonist) or **Nifedipine** (Calcium Channel Blocker) are preferred over $\beta_2$-agonists due to a better side-effect profile. * **Specific Side Effects:** $\beta_2$-agonists used as tocolytics can cause maternal tachycardia, palpitations, and **pulmonary edema**. * **Other Tocolytics:** Magnesium sulfate (acts by competing with Calcium) and Indomethacin (NSAID; inhibits prostaglandin synthesis).

Question 623: All the listed drugs have anti-androgenic effects EXCEPT:

A. Progesterone (Correct Answer)
B. Dutasteride
C. Flutamide
D. Spironolactone

Explanation: **Explanation:** The correct answer is **Progesterone**. While progesterone is a precursor to androgens in the biosynthetic pathway, it does not possess clinically significant anti-androgenic properties. In fact, some synthetic progestins (like medroxyprogesterone) can exhibit weak androgenic activity. **Why the other options are incorrect:** * **Dutasteride:** This is a **5-alpha reductase inhibitor**. It prevents the conversion of testosterone to the more potent dihydrotestosterone (DHT), thereby exerting an anti-androgenic effect. It is commonly used in Benign Prostatic Hyperplasia (BPH). * **Flutamide:** This is a **pure androgen receptor antagonist**. It competitively inhibits the binding of endogenous androgens to their receptors. It is primarily used in the management of metastatic prostatic carcinoma. * **Spironolactone:** Primarily an aldosterone antagonist (potassium-sparing diuretic), it also acts as a **weak androgen receptor antagonist** and inhibits steroidogenesis. It is frequently used off-label to treat hirsutism and acne in women. **High-Yield Clinical Pearls for NEET-PG:** * **Finasteride vs. Dutasteride:** Finasteride inhibits Type II 5-alpha reductase; Dutasteride inhibits both Type I and Type II isoenzymes. * **Cyproterone Acetate:** A progestin with significant anti-androgenic activity used in precocious puberty and severe hirsutism. * **Ketoconazole:** An antifungal that, at high doses, inhibits CYP17 (17,20-lyase), effectively inhibiting androgen synthesis; used in refractory prostate cancer or Cushing's syndrome. * **Bicalutamide:** Preferred over Flutamide in prostate cancer due to less hepatotoxicity and once-daily dosing.

Question 624: What is the only reliable symptom of hypoglycemia in a patient on beta-blocker therapy?

A. Tremor
B. Sweating (Correct Answer)
C. Tachycardia
D. Palpitations

Explanation: In a normal physiological response to hypoglycemia, the body triggers a massive sympathetic (adrenergic) discharge. This leads to "warning signs" such as tachycardia, palpitations, tremors, and anxiety, which are mediated by **$eta_1$ and $eta_2$ receptors** [1]. **Why Sweating is the Correct Answer:** Sweating (diaphoresis) is mediated by **cholinergic sympathetic nerves** acting on **muscarinic receptors**. Since beta-blockers only antagonize adrenergic receptors, they do not inhibit the cholinergic pathway responsible for sweating. Therefore, sweating remains the only reliable clinical sign of hypoglycemia in a patient taking beta-blockers, as it is not "masked" [1]. **Analysis of Incorrect Options:** * **Tachycardia and Palpitations (Options C & D):** These are mediated by $eta_1$ receptors in the heart. Beta-blockers prevent the increase in heart rate, effectively masking these early warning signs. * **Tremor (Option A):** This is mediated by $eta_2$ receptors in the skeletal muscles. Beta-blockers (especially non-selective ones like Propranolol) suppress tremors. **High-Yield NEET-PG Pearls:** 1. **The "Masking" Effect:** Beta-blockers are generally contraindicated or used with extreme caution in diabetic patients because they mask the autonomic warning signs of hypoglycemia, leading to potentially fatal "unawareness" [1, 2]. 2. **Hypertensive Crisis:** In addition to masking symptoms, non-selective beta-blockers can cause a paradoxical rise in blood pressure during hypoglycemia due to **unopposed alpha-adrenergic vasoconstriction**. 3. **Metabolic Effect:** Beta-blockers also inhibit glycogenolysis and gluconeogenesis, further delaying recovery from a hypoglycemic episode [1]. 4. **Exception:** Selective $eta_1$ blockers (e.g., Atenolol, Metoprolol) are safer than non-selective ones but can still partially mask symptoms [1].

Question 625: Which of the following medications can cause gynecomastia and infertility?

A. Flutamide
B. Cimetidine (Correct Answer)
C. Ranitidine
D. Methotrexate

Explanation: **Explanation:** **Cimetidine**, a first-generation H2-receptor antagonist, is a high-yield topic in NEET-PG due to its distinct endocrine side effects. It causes **gynecomastia and infertility** through two primary mechanisms: 1. **Anti-androgenic effects:** It acts as a competitive antagonist at androgen receptors, blocking the action of testosterone. 2. **Hyperprolactinemia:** It inhibits the metabolism of estradiol and can increase prolactin levels, further suppressing the hypothalamic-pituitary-gonadal axis. **Analysis of Options:** * **Flutamide (Option A):** While it is a potent competitive androgen receptor antagonist used in prostate cancer and *does* cause gynecomastia, it is generally not the classic answer associated with H2-blockers in this context. * **Ranitidine (Option C):** Unlike cimetidine, newer H2-blockers like ranitidine, famotidine, and nizatidine have negligible anti-androgenic effects and do not typically cause gynecomastia or impotence. * **Methotrexate (Option D):** This is a folate antimetabolite. While it can cause oligospermia (reversible infertility), it is not a recognized cause of gynecomastia. **Clinical Pearls for NEET-PG:** * **Cimetidine Mnemonic (DISCO):** Drugs causing gynecomastia: **D**igoxin, **I**soniazid, **S**pironolactone, **C**imetidine, **O**estrogens. * **Enzyme Inhibition:** Cimetidine is a potent **P450 inhibitor**, leading to significant drug interactions (e.g., increasing levels of Warfarin, Phenytoin, and Theophylline). * **Infertility:** Cimetidine-induced sperm count reduction is reversible upon discontinuation of the drug.

Question 626: Dopamine acts on D2 receptors, which have an inhibitory effect on prolactin secretion. If D2 receptors are blocked, which of the following effects will not be seen?

A. Visual disturbance (Correct Answer)
B. Gonadal dysfunction
C. Headache
D. Excessive lactation

Explanation: **Explanation:** The question tests the understanding of the **Tuberoinfundibular pathway** and the clinical manifestations of hyperprolactinemia. **1. Why "Visual Disturbance" is the correct answer:** Dopamine acts as the primary Prolactin Inhibiting Hormone (PIH). Blocking D2 receptors (e.g., by antipsychotics like Haloperidol or Metoclopramide) leads to **Hyperprolactinemia**. Visual disturbances (specifically bitemporal hemianopia) occur due to **mechanical compression** of the optic chiasm by a large pituitary tumor (Macroadenoma). Simply blocking D2 receptors increases prolactin levels biochemically but does not cause a physical mass effect or tumor growth; therefore, visual field defects will not be seen. **2. Analysis of Incorrect Options:** * **Gonadal dysfunction:** High prolactin inhibits the release of GnRH from the hypothalamus. This leads to decreased LH and FSH, resulting in infertility, amenorrhea in females, and decreased libido or impotence in males. * **Headache:** While more common with tumors, acute biochemical hyperprolactinemia and the underlying cause of D2 blockade can be associated with non-specific headaches. * **Excessive lactation (Galactorrhea):** This is a direct result of prolactin’s action on mammary glands, stimulating milk production in the absence of pregnancy. **Clinical Pearls for NEET-PG:** * **Drug-Induced Hyperprolactinemia:** The most common cause of elevated prolactin (after pregnancy). Key drugs include Antipsychotics, Reserpine, Metoclopramide, and Methyldopa. * **Dopamine Agonists:** Bromocriptine and **Cabergoline** (preferred due to higher D2 selectivity and longer half-life) are used to treat prolactinomas. * **Hook Effect:** A laboratory phenomenon where extremely high prolactin levels give a falsely low reading; requires sample dilution for accurate diagnosis.

Question 627: Compared to hydrocortisone, which of the following has the maximum glucocorticoid activity?

A. Cortisone
B. Prednisolone
C. Dexamethasone (Correct Answer)
D. Methylprednisolone

Explanation: ### Explanation The potency of corticosteroids is determined by their relative **glucocorticoid** (anti-inflammatory) and **mineralocorticoid** (salt-retaining) activities. Hydrocortisone (cortisol) is used as the standard reference with a potency ratio of 1:1. **Why Dexamethasone is Correct:** Dexamethasone is a long-acting synthetic glucocorticoid. It has the highest anti-inflammatory potency among the options provided, being approximately **25 to 30 times more potent than hydrocortisone**. Crucially, it possesses **zero mineralocorticoid activity**, making it ideal for conditions where fluid retention must be avoided (e.g., cerebral edema). **Analysis of Incorrect Options:** * **Cortisone:** This is a prodrug that must be converted to cortisol in the liver. It is actually *less* potent than hydrocortisone (0.8x potency). * **Prednisolone:** An intermediate-acting steroid with approximately **4 times** the anti-inflammatory potency of hydrocortisone. It retains some mineralocorticoid activity. * **Methylprednisolone:** Also an intermediate-acting steroid, it is slightly more potent than prednisolone, with approximately **5 times** the potency of hydrocortisone. **High-Yield NEET-PG Pearls:** 1. **Potency Hierarchy:** Dexamethasone = Betamethasone (25–30x) > Methylprednisolone (5x) > Prednisolone (4x) > Hydrocortisone (1x) > Cortisone (0.8x). 2. **Duration of Action:** Dexamethasone is **long-acting** (t½: 36–72 hours), whereas Prednisolone is intermediate-acting (t½: 12–36 hours). 3. **DOC for Fetal Lung Maturity:** Betamethasone or Dexamethasone are preferred because they poorly bind to transcortin and cross the placenta in active forms. 4. **Mineralocorticoid Powerhouse:** Fludrocortisone has the highest mineralocorticoid activity and is used in Addison’s disease.

Question 628: Biguanides act by which of the following mechanisms, except?

A. Stimulating insulin release from the pancreas (Correct Answer)
B. Promoting glycolysis
C. Inhibiting gluconeogenesis
D. Enhancing insulin binding to its receptors

Explanation: **Explanation:** **Biguanides (e.g., Metformin)** are classified as **euglycemic agents** or insulin sensitizers. Unlike Sulfonylureas and Meglitinides, they do not stimulate the pancreas to produce more insulin. **1. Why Option A is the Correct Answer (The "Except"):** Metformin does not act on the pancreatic beta cells to stimulate insulin secretion. Therefore, it does not cause hyperinsulinemia or hypoglycemia when used as monotherapy. This is the fundamental distinction between biguanides and "insulin secretagogues." **2. Analysis of Other Options:** * **Inhibiting Gluconeogenesis (Option C):** This is the **primary mechanism** of Metformin. It activates AMP-activated protein kinase (AMPK), which suppresses hepatic glucose production (gluconeogenesis) and glycogenolysis. * **Enhancing Insulin Binding (Option D):** Metformin increases the sensitivity of peripheral tissues (muscle and fat) to insulin by improving receptor binding and increasing the translocation of glucose transporters (GLUT-4) to the cell membrane. * **Promoting Glycolysis (Option B):** By activating AMPK, Metformin enhances anaerobic glycolysis in the tissues, which increases the peripheral utilization of glucose. **Clinical Pearls for NEET-PG:** * **Drug of Choice:** Metformin is the first-line drug for Type 2 Diabetes Mellitus, especially in obese patients, as it promotes modest weight loss. * **Adverse Effects:** The most common side effects are GI-related (diarrhea, metallic taste). The most serious, though rare, is **Lactic Acidosis** (due to inhibition of gluconeogenesis from lactate). * **Vitamin Deficiency:** Long-term use can lead to **Vitamin B12 deficiency** due to malabsorption. * **Contraindication:** It is contraindicated in patients with significant renal impairment (eGFR <30 mL/min) due to the risk of lactic acidosis.

Question 629: Pramlintide is?

A. Synthetic amylin analogue (Correct Answer)
B. Inhibitor of DPP 4
C. GLP 1 analogue
D. PPAR gamma

Explanation: **Explanation:** **Pramlintide** is a synthetic analogue of **Amylin**, a peptide hormone co-secreted with insulin by the pancreatic beta cells. In patients with Type 1 and Type 2 Diabetes, amylin levels are deficient. Pramlintide works by mimicking amylin’s physiological actions: it slows gastric emptying, suppresses postprandial glucagon secretion, and increases satiety (centrally mediated). It is notably the only non-insulin drug approved for use in **Type 1 Diabetes**, though it is also used in Type 2 Diabetes. **Analysis of Incorrect Options:** * **Option B (Inhibitor of DPP-4):** These are the "Gliptins" (e.g., Sitagliptin, Vildagliptin). They act by preventing the breakdown of endogenous GLP-1 and GIP. * **Option C (GLP-1 analogue):** These are the "Tides" (e.g., Exenatide, Liraglutide). While they share some effects with Pramlintide (like slowed gastric emptying), they primarily act by stimulating glucose-dependent insulin secretion. * **Option D (PPAR gamma):** This is the molecular target for **Thiazolidinediones** (e.g., Pioglitazone), which act as insulin sensitizers in peripheral tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Administered via **subcutaneous injection** immediately before meals. * **Key Side Effect:** Severe **hypoglycemia** (when used with insulin) and nausea. * **Contraindication:** Gastroparesis (due to its effect on slowing gastric motility). * **Weight Effect:** It is associated with **weight loss**, making it beneficial for obese diabetic patients.

Question 630: Which of the following antimicrobials are termed as type I calcimimetics that mimic the stimulatory effect of calcium on the calcium-sensing receptor to inhibit parathyroid hormone secretion by the parathyroid gland?

A. Streptomycin
B. Hamycin (Correct Answer)
C. Neomycin
D. Gentamicin

Explanation: ### Explanation **Concept Overview:** The Calcium-Sensing Receptor (CaSR) is a G protein-coupled receptor located primarily on the parathyroid glands. [1] It regulates the secretion of Parathyroid Hormone (PTH) in response to changes in extracellular calcium levels. [1], [2] **Calcimimetics** are agents that increase the sensitivity of these receptors to calcium, thereby suppressing PTH secretion. [1] They are classified into two types: * **Type I Calcimimetics:** Full agonists that directly activate the CaSR (e.g., certain polyvalent cations). * **Type II Calcimimetics:** Allosteric modulators that increase the receptor's sensitivity to calcium (e.g., Cinacalcet). [1] **Why Hamycin is Correct:** **Hamycin** is a polyene antifungal antibiotic (similar to Amphotericin B). Research has identified that Hamycin acts as a **Type I calcimimetic**. It mimics the stimulatory effect of calcium on the CaSR, leading to a potent inhibition of PTH secretion. This makes it a unique antimicrobial with significant endocrine-modulating properties. **Analysis of Incorrect Options:** * **A, C, and D (Aminoglycosides):** Streptomycin, Neomycin, and Gentamicin are aminoglycoside antibiotics. While aminoglycosides are known to interact with various ion channels and can occasionally cause electrolyte disturbances (like hypomagnesemia or hypocalcemia via Bartter-like syndrome), they are not classified as Type I calcimimetics in the context of direct PTH suppression via CaSR activation. **NEET-PG High-Yield Pearls:** * **Cinacalcet:** The most commonly asked Type II calcimimetic; used in secondary hyperparathyroidism (CKD) and parathyroid carcinoma. [1] * **Etelcalcetide:** An intravenous calcimimetic used for patients on hemodialysis. * **Clinical Application:** Calcimimetics are crucial because they lower PTH levels without increasing calcium or phosphorus levels, unlike Vitamin D analogues. * **Hamycin Fact:** It is an Indian-discovered antifungal (produced by *Streptomyces pimprina*).

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

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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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