Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 551: Which of the following is an anti-androgenic drug?

A. Bicalutamide (Correct Answer)
B. Oxymetholone
C. Raloxifene
D. Stanozolol

Explanation: **Explanation:** **Bicalutamide** is the correct answer because it is a potent, non-steroidal **androgen receptor antagonist**. It works by competitively inhibiting the binding of dihydrotestosterone (DHT) and testosterone to their receptors. * **Clinical Use:** It is primarily used in the management of metastatic **prostate cancer**, often combined with GnRH analogs to prevent the "testosterone flare" phenomenon. **Analysis of Incorrect Options:** * **Oxymetholone & Stanozolol (Options B & D):** These are **anabolic steroids** (synthetic derivatives of testosterone). Instead of blocking androgens, they mimic them. They are used clinically for hereditary angioedema or certain types of anemia but are frequently misused for performance enhancement. * **Raloxifene (Option C):** This is a **Selective Estrogen Receptor Modulator (SERM)**. It acts as an estrogen agonist in the bone (preventing osteoporosis) and an antagonist in the breast and uterus (reducing cancer risk). It has no direct anti-androgenic activity. **High-Yield NEET-PG Pearls:** 1. **Pure Anti-androgens:** Bicalutamide, Flutamide, and Enzalutamide. Bicalutamide is preferred over Flutamide due to its longer half-life and lower risk of hepatotoxicity. 2. **5-alpha Reductase Inhibitors:** Finasteride and Dutasteride (prevent conversion of Testosterone to DHT); used in BPH and male pattern baldness. 3. **Spironolactone:** A potassium-sparing diuretic that also has anti-androgenic properties, often used in treating hirsutism in females. 4. **Abiraterone:** Inhibits CYP17A1, blocking the synthesis of androgens in the testes, adrenals, and tumor tissue.

Question 552: Sulphonylureas act by:

A. Reducing the absorption of carbohydrate from the gut
B. Stimulating the beta islet cells of the pancreas to release insulin (Correct Answer)
C. Increasing the uptake of glucose in peripheral tissue
D. Reducing hepatic gluconeogenesis

Explanation: **Mechanism of Action: Sulphonylureas** **Correct Answer: B. Stimulating the beta islet cells of the pancreas to release insulin** Sulphonylureas (e.g., Glibenclamide, Glipizide, Glimepiride) are classified as **insulin secretagogues**. They act by binding to a specific **SUR1 receptor** on the ATP-sensitive potassium ($K_{ATP}$) channels located on the membrane of pancreatic beta-islet cells. This binding causes the closure of $K_{ATP}$ channels, leading to cell depolarization. This depolarization opens voltage-gated calcium channels, causing an influx of $Ca^{2+}$, which ultimately triggers the exocytosis of stored insulin granules. **Explanation of Incorrect Options:** * **Option A:** This describes the mechanism of **Alpha-glucosidase inhibitors** (e.g., Acarbose, Voglibose), which delay carbohydrate digestion and absorption in the proximal small intestine. * **Option C:** This is a secondary effect of **Biguanides (Metformin)** and **Thiazolidinediones (Pioglitazone)**, which act as insulin sensitizers by activating AMPK and PPAR-gamma receptors, respectively. * **Option D:** This is the primary mechanism of **Metformin**, which suppresses hepatic glucose production (gluconeogenesis) via AMPK activation. **High-Yield Clinical Pearls for NEET-PG:** * **Prerequisite:** Sulphonylureas require functional beta cells to work; hence, they are ineffective in Type 1 Diabetes. * **Side Effects:** The most common side effect is **hypoglycemia**, and the most common metabolic side effect is **weight gain**. * **Generation Gap:** Second-generation agents (Glimepiride) are more potent and have a lower risk of hypoglycemia compared to first-generation agents (Tolbutamide). * **Disulfiram-like reaction:** Classically associated with first-generation sulphonylureas like Chlorpropamide.

Question 553: What is the advantage of desmopressin over vasopressin in the treatment of diabetes insipidus?

A. Causes less formation of factor VIII
B. Causes less hypernatremia
C. Is more selective for V2 receptor subtype (Correct Answer)
D. Provides greater relief of excessive thirst the patient is experiencing

Explanation: **Explanation:** **1. Why Option C is Correct:** Vasopressin (ADH) acts on two primary receptors: **V1** (located on vascular smooth muscle, causing vasoconstriction) and **V2** (located in the renal collecting ducts, causing water reabsorption). **Desmopressin (dDAVP)** is a synthetic analogue of vasopressin designed to be highly selective for the **V2 receptor**. By minimizing V1 activity, desmopressin effectively treats Diabetes Insipidus (DI) by concentrating urine without causing the unwanted systemic vasoconstriction (hypertension, angina, or abdominal cramps) associated with native vasopressin. It also has a significantly longer duration of action (6–20 hours) compared to vasopressin (2–8 hours). **2. Why Other Options are Wrong:** * **Option A:** Desmopressin actually **increases** the release of Factor VIII and von Willebrand factor from endothelial cells (via V2-like receptors). This makes it a treatment for Hemophilia A and von Willebrand Disease, not a disadvantage. * **Option B:** Both drugs treat DI, which helps correct hypernatremia. However, the primary risk of overdose with both is **hyponatremia** (due to excessive water retention), not hypernatremia. * **Option D:** While both drugs reduce polyuria and secondary thirst, desmopressin is preferred due to its **selectivity and duration**, not because it has a superior direct effect on the thirst center. **3. NEET-PG High-Yield Pearls:** * **Route of Choice:** Intranasal is common, but oral and IV/SC routes are available. * **Drug of Choice (DOC):** Desmopressin is the DOC for **Central Diabetes Insipidus** and **Nocturnal Enuresis**. * **V1 vs. V2:** Remember **V1 = Vascular** (Constriction); **V2 = Volume/Valves** (Water reabsorption and Factor VIII/vWF release). * **Terlipressin:** A V1-selective analogue used in esophageal varices.

Question 554: What is the drug of choice for managing Type 2 Diabetes Mellitus in a patient with hypertension and obesity?

A. Glibenclamide
B. Metformin
C. Vildagliptin
D. Empagliflozin (Correct Answer)

Explanation: **Explanation:** The management of Type 2 Diabetes Mellitus (T2DM) has shifted from a glucose-centric approach to one focused on **cardiorenal protection**. **Why Empagliflozin is the Correct Answer:** Empagliflozin is an **SGLT-2 inhibitor**. It is the drug of choice in this scenario due to its pleiotropic effects: 1. **Weight Loss:** It induces osmotic diuresis and glucosuria (losing ~300 kcal/day), making it ideal for obese patients. 2. **Blood Pressure Reduction:** The natriuretic effect helps lower systolic blood pressure. 3. **Cardiovascular Benefit:** Large trials (EMPA-REG) proved it reduces Major Adverse Cardiovascular Events (MACE) and hospitalization for heart failure, which is critical for hypertensive diabetics. **Analysis of Incorrect Options:** * **Glibenclamide (Sulfonylurea):** Causes significant **weight gain** and carries a high risk of hypoglycemia. It offers no cardiovascular protection. * **Metformin (Biguanide):** While it is weight-neutral and the traditional first-line agent, current ADA/EASD guidelines prioritize SGLT-2 inhibitors or GLP-1 agonists over Metformin in patients with established atherosclerotic cardiovascular disease (ASCVD) or high CV risk factors (like hypertension and obesity). * **Vildagliptin (DPP-4 Inhibitor):** It is weight-neutral and has a low risk of hypoglycemia but does not provide the superior weight loss or blood pressure benefits seen with SGLT-2 inhibitors. **High-Yield Clinical Pearls for NEET-PG:** * **SGLT-2 Inhibitors Side Effects:** Increased risk of Genital Mycotic Infections (Candidiasis) and Euglycemic Ketoacidosis. * **Drug of Choice for T2DM + Heart Failure:** SGLT-2 inhibitors (e.g., Dapagliflozin, Empagliflozin). * **Drug of Choice for T2DM + CKD (with proteinuria):** SGLT-2 inhibitors are now preferred for their renoprotective effects.

Question 555: Bisphosphonates are used for which of the following conditions, EXCEPT?

A. Osteolytic bone metastases
B. Osteoporosis
C. Osteosclerosis (Correct Answer)
D. Paget's disease

Explanation: **Explanation:** **Bisphosphonates** (e.g., Alendronate, Zoledronate) are structural analogs of pyrophosphate that primarily act by inhibiting **osteoclasts**, the cells responsible for bone resorption. **Why Osteosclerosis is the Correct Answer:** **Osteosclerosis** is a condition characterized by an abnormal increase in bone density (hardening of bone). Since bisphosphonates inhibit bone breakdown and further increase bone mineral density, they would potentially worsen the condition or provide no therapeutic benefit. Therefore, they are not indicated here. **Analysis of Incorrect Options:** * **Osteoporosis (Option B):** This is the most common indication. Bisphosphonates are first-line drugs that decrease bone resorption, thereby increasing bone mass and reducing the risk of fractures. * **Osteolytic Bone Metastases (Option A):** Cancers (like breast or multiple myeloma) often cause "punched-out" lytic lesions by activating osteoclasts. Bisphosphonates (especially IV Zoledronate) inhibit this process, reducing bone pain and pathological fractures. * **Paget’s Disease (Option D):** This involves disordered, excessive bone remodeling. Bisphosphonates are the treatment of choice to suppress the overactive osteoclasts and normalize bone turnover. **NEET-PG High-Yield Pearls:** * **Mechanism:** They bind to hydroxyapatite crystals and inhibit the enzyme **FPPS (Farnesyl Pyrophosphate Synthase)** in the mevalonate pathway of osteoclasts. * **Administration:** Oral bisphosphonates must be taken on an empty stomach with a full glass of water, and the patient must remain upright for 30 minutes to prevent **erosive esophagitis**. * **Side Effects:** Osteonecrosis of the Jaw (ONJ) and atypical subtrochanteric fractures (with long-term use). * **Drug of Choice:** Zoledronate is the most potent bisphosphonate and is the drug of choice for **Hypercalcemia of Malignancy**.

Question 556: Table sugar can be used for the treatment of hypoglycemia secondary to all of the following drugs EXCEPT:

A. Acarbose (Correct Answer)
B. Metformin
C. Glipizide
D. Insulin

Explanation: The correct answer is **Acarbose**. **Mechanism of Action & Rationale:** Acarbose and Miglitol are **$\alpha$-glucosidase inhibitors**. These drugs act in the brush border of the small intestine to inhibit the enzyme $\alpha$-glucosidase, which is responsible for breaking down complex carbohydrates (polysaccharides) and **table sugar (sucrose)** into simple monosaccharides like glucose and fructose [1], [4]. If a patient taking Acarbose develops hypoglycemia, consuming table sugar (sucrose) will be ineffective because the drug prevents its breakdown and absorption [2]. Therefore, **pure glucose (dextrose)** must be administered, as it is a monosaccharide that can be absorbed directly without enzymatic cleavage [2]. **Analysis of Incorrect Options:** * **Glipizide (Sulfonylurea) & Insulin:** These drugs cause hypoglycemia by increasing systemic insulin levels [3]. They do not interfere with intestinal carbohydrate absorption. Therefore, oral sucrose (table sugar) is rapidly broken down and absorbed, effectively reversing the hypoglycemia. * **Metformin:** While Metformin rarely causes hypoglycemia when used as monotherapy, if it occurs in combination therapy, sucrose can still be absorbed normally because Metformin does not inhibit $\alpha$-glucosidase [1]. **Clinical Pearls for NEET-PG:** * **Drug of Choice for Acarbose-induced hypoglycemia:** Oral Glucose/Dextrose (NOT Sucrose) [2]. * **Common Side Effects of Acarbose:** Flatulence, bloating, and diarrhea (due to fermentation of undigested carbohydrates by colonic bacteria) [1]. * **Contraindication:** Inflammatory Bowel Disease (IBD) or intestinal obstruction. * **Key Concept:** $\alpha$-glucosidase inhibitors only delay carbohydrate absorption; they do not alter the total amount absorbed [1].

Question 557: Meglitinide analogues act by which mechanism?

A. Increasing insulin release (Correct Answer)
B. Decreasing glucagon release
C. Decreasing intestinal absorption of glucose
D. Promoting peripheral utilization of glucose

Explanation: Meglitinide analogues (e.g., **Repaglinide, Nateglinide**) are known as **"Prandial Glucose Regulators."** [1], [2], [3] Like Sulfonylureas, they act as insulin secretagogues. [1], [2] They bind to a specific site on the **ATP-sensitive K⁺ channels** in the pancreatic β-cell membrane (distinct from the Sulfonylurea receptor site). [1], [2], [3] This binding causes the channels to close, leading to cell depolarization, an influx of Calcium (Ca²⁺), and subsequent exocytosis of insulin. [2] Their rapid onset and short duration of action make them ideal for controlling postprandial hyperglycemia. [1], [2], [3] **Analysis of Incorrect Options:** * **B (Decreasing glucagon release):** This is a secondary effect of GLP-1 agonists and DPP-4 inhibitors, but not the primary mechanism of Meglitinides. * **C (Decreasing intestinal absorption):** This describes the mechanism of **Alpha-glucosidase inhibitors** (e.g., Acarbose, Voglibose), which delay carbohydrate digestion. * **D (Promoting peripheral utilization):** This is the primary mechanism of **Biguanides (Metformin)** and **Thiazolidinediones (Pioglitazone)**, which act as insulin sensitizers in muscle and adipose tissue. **High-Yield Clinical Pearls for NEET-PG:** * **Rapid Onset:** Meglitinides should be taken **15–30 minutes before meals** ("Skip a meal, skip a dose"). [1], [3] * **Safety in Renal Impairment:** Repaglinide is primarily excreted via bile, making it safer for patients with **renal insufficiency** compared to most Sulfonylureas. * **Side Effects:** The most common side effect is hypoglycemia (though less frequent than with long-acting Sulfonylureas) and weight gain. [3] * **Nateglinide** is a D-phenylalanine derivative [1], [2], whereas **Repaglinide** is a benzoic acid derivative.

Question 558: Which of the following statements regarding the mechanism of action of sulfonylureas is true?

A. Increase peripheral utilization of glucose
B. Reduce hepatic glucose output
C. Act on SUR1 receptors on the pancreatic beta cell membrane (Correct Answer)
D. Increase transcription of genes regulating glucose metabolism

Explanation: **Explanation:** **Mechanism of Action (The Correct Answer):** Sulfonylureas (e.g., Glibenclamide, Glimepiride) are **insulin secretagogues**. They act by binding to the **Sulfonylurea Receptor 1 (SUR1)**, which is a subunit of the ATP-sensitive potassium ($K_{ATP}$) channel located on the pancreatic beta-cell membrane. 1. Binding leads to the **closure of $K_{ATP}$ channels**, preventing potassium efflux. 2. This causes **depolarization** of the cell membrane. 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 & B:** These are the primary mechanisms of **Biguanides (Metformin)**. Metformin activates AMPK, which decreases hepatic gluconeogenesis (output) and improves insulin sensitivity in peripheral tissues (skeletal muscle). Sulfonylureas primarily focus on insulin release, not sensitivity. * **Option D:** This describes the mechanism of **Thiazolidinediones (TZDs)** like Pioglitazone. TZDs act as ligands for the **PPAR-$\gamma$** nuclear receptor, which modulates the transcription of genes involved in lipid and glucose metabolism. **High-Yield NEET-PG Pearls:** * **Site of Action:** Sulfonylureas require functional beta cells; hence, they are ineffective in Type 1 Diabetes. * **Side Effects:** The most common side effect is **hypoglycemia**, and the most notorious for causing prolonged hypoglycemia is **Chlorpropamide** (1st Gen). **Weight gain** is also a significant side effect. * **Safety:** **Glipizide** is preferred in patients with renal impairment as it is primarily metabolized by the liver. * **Disulfiram-like reaction:** Classically associated with first-generation sulfonylureas (Chlorpropamide).

Question 559: Which of the following antibiotic can be used in SIADH?

A. Doxycycline
B. Minocycline
C. Tigecycline
D. Demeclocycline (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Demeclocycline** **Mechanism and Rationale:** SIADH (Syndrome of Inappropriate Antidiuretic Hormone) is characterized by excessive ADH secretion, leading to water retention and hyponatremia. **Demeclocycline**, a tetracycline derivative, is unique because it acts as a **selective ADH antagonist** at the level of the renal collecting ducts [1]. It induces a state of "nephrogenic diabetes insipidus" by inhibiting the intracellular signaling (cAMP formation) triggered by ADH, thereby promoting water excretion [1]. While Tolvaptan (V2 receptor antagonist) is now the preferred treatment, Demeclocycline remains a classic pharmacological alternative for chronic SIADH management [1]. **Analysis of Incorrect Options:** * **A. Doxycycline:** A broad-spectrum tetracycline primarily used for respiratory, genital, and tick-borne infections. It lacks the specific ADH-antagonizing property required to treat SIADH. * **B. Minocycline:** Commonly used for acne and certain MRSA infections due to its high lipophilicity. Like doxycycline, it does not interfere with ADH action in the kidney. * **C. Tigecycline:** A glycylcycline used for complicated skin and intra-abdominal infections. It is administered IV and has no role in managing water-electrolyte imbalances. **High-Yield Clinical Pearls for NEET-PG:** * **Drug-Induced SIADH:** Common culprits include **Chlorpropamide**, **Cyclophosphamide**, **SSRIs**, and **Carbamazepine** [1]. * **Adverse Effect:** The primary side effect of Demeclocycline when used for SIADH is potential **nephrotoxicity** and photosensitivity. * **Drug of Choice:** For acute, symptomatic hyponatremia in SIADH, the treatment of choice is **Hypertonic Saline (3%)** [1]. For chronic management, **Vaptans** (Tolvaptan, Conivaptan) are now preferred over Demeclocycline [1]. * **Caution:** Rapid correction of hyponatremia can lead to **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis).

Question 560: Which of the following decreases thyroid hormone on a long-term basis?

A. T4
B. I131 (Correct Answer)
C. Calcitriol
D. Fluorouracil

Explanation: **Explanation:** The correct answer is **I131 (Radioactive Iodine)**. **Mechanism of Action:** I131 is the isotope of choice for treating hyperthyroidism (Graves' disease) and thyroid carcinoma. It is orally administered and rapidly trapped by the thyroid gland. It emits **beta particles**, which have a short penetration range (0.5–2 mm). This results in the selective pyknosis and necrosis of follicular cells, followed by fibrosis. Unlike antithyroid drugs (like Carbimazole), which only inhibit hormone synthesis, I131 causes **permanent destruction** of the thyroid parenchyma, leading to a long-term, irreversible decrease in thyroid hormone levels. **Analysis of Incorrect Options:** * **A. T4 (Levothyroxine):** This is exogenous thyroid hormone used for replacement therapy. Administering T4 increases systemic thyroid hormone levels; it does not decrease them. * **C. Calcitriol:** This is the active form of Vitamin D (1,25-dihydroxyvitamin D3). It regulates calcium and phosphate homeostasis but has no direct inhibitory effect on the synthesis or release of thyroid hormones (T3/T4). * **D. Fluorouracil (5-FU):** This is a pyrimidine analogue used as a cytotoxic chemotherapy agent. While it affects rapidly dividing cells, it is not used to modulate thyroid function. **High-Yield Clinical Pearls for NEET-PG:** * **Wolff-Chaikoff Effect:** A transient decrease in thyroid hormone levels caused by high doses of *stable* iodine (Lugol's iodine), usually lasting only 10–14 days. * **Contraindication:** I131 is strictly **contraindicated in pregnancy** (crosses the placenta and destroys the fetal thyroid) and during breastfeeding. * **Side Effect:** The most common long-term complication of I131 therapy is **hypothyroidism**, requiring lifelong T4 supplementation. * **Monitoring:** The clinical response to I131 is slow, taking 2–3 months for full effect.

Practice by Chapter

Hypothalamic and Pituitary Hormones

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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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