Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 281: What is the drug of choice for treating insulinoma?

A. Glucagon
B. Sodium nitroprusside
C. Diazoxide (Correct Answer)
D. Mecasermin

Explanation: **Explanation:** **Why Diazoxide is the correct answer:** Diazoxide is the drug of choice for the medical management of **insulinoma** (an insulin-secreting pancreatic islet cell tumor). It acts as a **K⁺ channel opener** in the pancreatic beta cells. By keeping the ATP-sensitive potassium channels open, it hyperpolarizes the cell membrane, thereby inhibiting the release of insulin. This effectively counteracts the hyperinsulinism and prevents severe hypoglycemia. **Analysis of Incorrect Options:** * **A. Glucagon:** While glucagon can acutely raise blood glucose levels in emergency hypoglycemic episodes, it is not used for long-term management of insulinoma. Its effect is transient and it may paradoxically stimulate further insulin release from the tumor. * **B. Sodium nitroprusside:** This is a potent vasodilator used in hypertensive emergencies. While it shares a structural similarity to diazoxide (which also has vasodilatory properties), nitroprusside has no effect on insulin secretion. * **C. Mecasermin:** This is a recombinant human Insulin-like Growth Factor-1 (rhIGF-1) used to treat growth failure in children with severe primary IGF-1 deficiency. It actually has insulin-like hypoglycemic effects, which would worsen the condition. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Diazoxide is a "K⁺ channel opener" (opposite to Sulfonylureas, which are K⁺ channel blockers). * **Side Effects:** A significant side effect of Diazoxide is **hypertrichosis** (excessive hair growth) and fluid retention. * **Other Uses:** Historically used as an IV vasodilator for hypertensive crises, though now obsolete for that indication. * **Surgical Note:** Surgery (resection) remains the definitive treatment for insulinoma; Diazoxide is used for patients who are not surgical candidates or for preoperative stabilization.

Question 282: Which type of insulin is indicated in diabetic ketoacidosis?

A. Lente insulin subcutaneously
B. Soluble insulin subcutaneously
C. Protamine zinc insulin intramuscularly
D. Soluble insulin intravenously infusion (Correct Answer)

Explanation: **Explanation:** **1. Why Soluble Insulin Intravenously is Correct:** Diabetic Ketoacidosis (DKA) is a medical emergency characterized by severe dehydration, acidosis, and hyperglycemia [4]. **Soluble (Regular) insulin** is the drug of choice because it is the only form that can be administered intravenously [3]. The IV route is preferred in DKA for two reasons: * **Rapid Onset:** It provides an immediate effect to suppress lipolysis and ketogenesis. * **Titratability:** It has a short half-life (approx. 5–10 minutes) when given IV, allowing clinicians to adjust the infusion rate precisely based on hourly blood glucose monitoring [1]. **2. Why Other Options are Incorrect:** * **Lente and Protamine Zinc Insulin (Options A & C):** These are intermediate and long-acting "cloudy" insulins. They contain particles (zinc or protamine) that delay absorption. They are strictly contraindicated for IV use as they can cause embolic phenomena and have a delayed onset, making them useless in an acute crisis. * **Subcutaneous Route (Options A & B):** In DKA, patients often suffer from peripheral circulatory collapse (shock) and dehydration [4]. Subcutaneous absorption becomes erratic and unpredictable in such states. Therefore, the IV route is mandatory until the patient is stable [3]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Standard Protocol:** Low-dose IV insulin infusion (0.1 units/kg/hr) is the current standard of care [3]. * **The "Switch":** Transition to subcutaneous insulin only when the anion gap has closed and the patient is able to eat. * **Potassium Warning:** Insulin shifts potassium into cells. Always monitor K+ levels; if K+ is <3.3 mEq/L, delay insulin until potassium is replaced to avoid fatal arrhythmias [3][4]. * **Drug of Choice for Pregnancy:** Insulin remains the preferred agent for Gestational Diabetes Mellitus (GDM) [2].

Question 283: A disulfiram-like reaction is seen with which of the following drugs?

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

Explanation: **Explanation:** **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. Patients experience flushing, tachycardia, nausea, and palpitations (the "Antabuse effect"). Additionally, chlorpropamide is unique for causing SIADH (Syndrome of Inappropriate Antidiuretic Hormone), leading to dilutional hyponatremia. **Analysis of Incorrect Options:** * **Phenformin (A):** A biguanide (like metformin) that was withdrawn globally primarily due to a high risk of **lactic acidosis**, not disulfiram-like reactions. * **Glibenclamide (C):** A second-generation sulfonylurea. While second-generation agents are more potent and have fewer side effects, they generally do not cause disulfiram-like reactions or SIADH, unlike their first-generation counterparts. * **Exenatide (D):** A GLP-1 receptor agonist administered via injection. Its primary side effects are gastrointestinal (nausea, vomiting) and a risk of pancreatitis; it has no association with alcohol metabolism interference. **High-Yield Clinical Pearls for NEET-PG:** * **Other drugs causing Disulfiram-like reactions:** Metronidazole (most common), Tinidazole, Cefotetan, Cefoperazone, Griseofulvin, and Procarbazine. * **Chlorpropamide Mnemonic:** Remember the **"Two C's"** for Chlorpropamide: **C**heek flushing (Disulfiram-like) and **C**oncentrated urine (SIADH). * First-generation sulfonylureas (Tolbutamide, Chlorpropamide) are rarely used now due to long half-lives and higher side-effect profiles compared to second-generation agents (Glipizide, Gliclazide).

Question 284: Which of the following drugs is a somatostatin analog?

A. Octreotide (Correct Answer)
B. Abarelix
C. Goserelin
D. Nafarelin

Explanation: No explanation text provided. **Explanation:** **1. Why Octreotide is correct:** **Octreotide** is a synthetic octapeptide analog of **somatostatin** (Growth Hormone Inhibiting Hormone) [1]. While natural somatostatin has a very short half-life (approx. 2 minutes), octreotide is much more potent and has a longer half-life (approx. 1.5 hours), making it clinically useful [1]. It acts by binding to somatostatin receptors (SSTR-2 and SSTR-5), leading to the inhibition of growth hormone (GH), glucagon, insulin, and various gastrointestinal hormones [2][3]. **2. Why the other options are incorrect:** * **Abarelix:** This is a **GnRH receptor antagonist** [5]. It is primarily used in the management of advanced prostate cancer to rapidly suppress testosterone levels without the initial "flare" seen with agonists [5]. * **Goserelin & Nafarelin:** These are **GnRH (Gonadotropin-Releasing Hormone) agonists**. While they initially stimulate FSH and LH, continuous administration leads to the downregulation of GnRH receptors, resulting in medical castration. They are used for endometriosis, precocious puberty, and prostate cancer. **3. High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic Uses of Octreotide:** Acromegaly, secretory diarrheas (Carcinoid syndrome, VIPoma), and acute management of bleeding esophageal varices (by reducing splanchnic blood flow) [3][4]. * **Side Effects:** Biliary sludge and **gallstones** (due to inhibition of cholecystokinin and gallbladder contractility), steatorrhea, and nausea [3][4]. * **Other Analogs:** Lanreotide and Pasireotide (used specifically for Cushing’s disease) [2]. * **Mnemonic:** Remember **"S-O-L"** for Somatostatin analogs: **S**omatostatin, **O**ctreotide, **L**anreotide.

Question 285: Which of the following is NOT a mode of action of sulfonamides?

A. Activating receptors on beta cells of the pancreas to release insulin.
B. Inhibiting gluconeogenesis in the liver.
C. Enhancing insulin-mediated post-receptor enzyme reactions.
D. Decreasing glucose absorption from the gut. (Correct Answer)

Explanation: **Explanation:** Sulfonylureas (often referred to in this context as sulfonamide derivatives) are insulin secretagogues used in Type 2 Diabetes Mellitus. Their primary mechanism involves stimulating the pancreas, but they also possess significant extrapancreatic effects. **Why Option D is Correct:** **Decreasing glucose absorption from the gut** is the mechanism of action of **Alpha-glucosidase inhibitors** (e.g., Acarbose, Miglitol) and, to a lesser extent, Biguanides (Metformin). Sulfonylureas have no pharmacological effect on intestinal glucose transport or carbohydrate digestion. **Analysis of Incorrect Options:** * **Option A:** This is the **primary pancreatic action**. Sulfonylureas bind to the SUR1 subunit of ATP-sensitive K⁺ channels on beta-cell membranes, causing channel closure, depolarization, calcium influx, and subsequent insulin release. * **Option B:** This is an **extrapancreatic action**. Sulfonylureas reduce hepatic glucose production by inhibiting gluconeogenesis and glycogenolysis, thereby improving fasting plasma glucose. * **Option C:** Sulfonylureas increase **peripheral insulin sensitivity** by enhancing post-receptor signaling and increasing the number/sensitivity of insulin receptors on target tissues like muscle and fat. **High-Yield NEET-PG Pearls:** * **Generations:** First-gen (Tolbutamide - shortest acting) vs. Second-gen (Glimepiride - most potent). * **Side Effects:** Hypoglycemia (most common) and weight gain. * **Disulfiram-like reaction:** Classically associated with **Chlorpropamide**. * **Safety in Renal Failure:** **Gliquidone** is primarily excreted in bile, making it safer in renal impairment. * **K-ATP Channels:** These drugs also affect cardiac K-ATP channels; however, **Glimepiride** is considered more "pancreato-selective."

Question 286: Prolonged use of steroids may cause which of the following?

A. Decrease in bone matrix protein (Correct Answer)
B. Hypoglycemia
C. Hypotension
D. Early healing of wound

Explanation: ### Explanation **Correct Answer: A. Decrease in bone matrix protein** Prolonged use of glucocorticoids leads to **Glucocorticoid-Induced Osteoporosis (GIOP)** through several mechanisms. Steroids inhibit **osteoblasts** (bone-forming cells) and stimulate **osteoclasts** (bone-resorbing cells). Crucially, they decrease the synthesis of **Type I collagen** and other bone matrix proteins, leading to a reduction in the organic matrix (osteoid). Additionally, steroids decrease intestinal calcium absorption and increase renal calcium excretion, further weakening the bone. **Why the other options are incorrect:** * **B. Hypoglycemia:** Steroids are "diabetogenic." They stimulate gluconeogenesis and decrease peripheral glucose uptake, leading to **hyperglycemia**, not hypoglycemia. * **C. Hypotension:** Steroids have mineralocorticoid activity (causing sodium and water retention) and sensitize blood vessels to catecholamines. This typically results in **hypertension**. * **D. Early healing of wound:** Steroids **delay wound healing** by inhibiting fibroblast proliferation, reducing collagen synthesis, and suppressing the inflammatory response necessary for tissue repair. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site of steroid-induced fracture:** Vertebrae (followed by the femoral neck). * **Avascular Necrosis (AVN):** A serious complication of long-term steroid use, most commonly affecting the **head of the femur**. * **Prophylaxis:** Patients on long-term steroids should be started on **Calcium, Vitamin D, and Bisphosphonates** (the drug of choice for GIOP). * **Ocular side effects:** Steroids can cause **posterior subcapsular cataracts** and **glaucoma** (due to increased intraocular pressure).

Question 287: Which of the following conditions is a primary indication for the use of prostaglandins?

A. Missed abortion (Correct Answer)
B. Second-trimester abortion
C. Ectopic pregnancy
D. Postpartum hemorrhage (PPH)

Explanation: **Explanation:** Prostaglandins (PGs) are potent stimulators of uterine smooth muscle contraction and are essential in obstetric practice for cervical ripening and uterine evacuation. **Why Missed Abortion is the Primary Indication:** In a **missed abortion**, the products of conception are retained despite fetal demise. Prostaglandins, specifically **Misoprostol (PGE1)**, are the drug of choice for medical management. They act by softening and dilating the cervix (cervical ripening) and inducing myometrial contractions to expel the retained tissue, avoiding the need for invasive surgical evacuation in many cases. **Analysis of Incorrect Options:** * **Second-trimester abortion:** While PGs (like Carboprost or Misoprostol) are used, they are often part of a combined regimen with Mifepristone. In the context of "primary" pharmacological management of a non-viable pregnancy, missed abortion is the classic indication. * **Ectopic pregnancy:** This is a **contraindication** for prostaglandin use. The primary medical management for an unruptured ectopic pregnancy is **Methotrexate** (a folate antagonist). * **Postpartum hemorrhage (PPH):** While **Carboprost (PGF2α)** and Misoprostol are used in PPH, they are typically **second-line** agents. **Oxytocin** remains the primary drug of choice for both the prevention and initial treatment of PPH. **High-Yield NEET-PG Pearls:** * **Misoprostol (PGE1):** Orally active, stable at room temperature; used for missed abortion and NSAID-induced peptic ulcers. * **Dinoprostone (PGE2):** Most commonly used for induction of labor (cervical ripening). * **Carboprost (15-methyl PGF2α):** Used for refractory PPH; contraindicated in **Asthma** due to bronchoconstriction. * **Gemeprost (PGE1 analog):** Specifically used for second-trimester abortions via vaginal suppository.

Question 288: Which of the following drugs can cause hyperthyroidism?

A. Clonidine
B. Amiodarone (Correct Answer)
C. Hydralazine
D. Penicillamine

Explanation: **Explanation:** **Amiodarone** is a Class III antiarrhythmic drug with a unique chemical structure containing approximately **37% iodine by weight**. This high iodine content is the primary reason it can induce thyroid dysfunction. **Why Amiodarone is the correct answer:** Amiodarone can cause hyperthyroidism through two distinct mechanisms, collectively known as **Amiodarone-Induced Thyrotoxicosis (AIT)**: 1. **Type 1 AIT (Jod-Basedow Phenomenon):** Excess iodine from the drug acts as a substrate for increased thyroid hormone synthesis in patients with underlying multinodular goiter or latent Graves' disease. 2. **Type 2 AIT:** The drug exerts a direct toxic effect on thyroid follicular cells, causing destructive thyroiditis and the leakage of preformed hormones into the circulation. *Note: Amiodarone can also cause hypothyroidism via the **Wolff-Chaikoff effect**.* **Why the other options are incorrect:** * **Clonidine (A):** An alpha-2 agonist used for hypertension; it does not affect iodine metabolism or thyroid function. * **Hydralazine (C):** A direct vasodilator used in hypertensive emergencies; its most notable side effect is Drug-Induced Lupus Erythematosus (DILE). * **Penicillamine (D):** A chelating agent used in Wilson’s disease; it is associated with nephrotic syndrome and skin changes, but not hyperthyroidism. **High-Yield Clinical Pearls for NEET-PG:** * **Half-life:** Amiodarone has an exceptionally long half-life (~58 days), meaning thyroid toxicity can persist months after discontinuation. * **Other drugs causing Hyperthyroidism:** Lithium (rarely, though more commonly causes hypothyroidism), Interferon-alpha, and Checkpoint inhibitors (e.g., Pembrolizumab). * **Monitoring:** Baseline and periodic Thyroid Function Tests (TFTs) are mandatory for all patients on Amiodarone.

Question 289: What is the most common side effect seen with bisphosphonates?

A. Cholelithiasis
B. Constipation
C. Erosive esophagitis (Correct Answer)
D. Osteonecrosis

Explanation: **Explanation:** **Bisphosphonates** (e.g., Alendronate, Risedronate) are the first-line treatment for osteoporosis. The most common side effect associated with oral bisphosphonates is **erosive esophagitis** and gastrointestinal irritation. **Why Erosive Esophagitis is the Correct Answer:** Oral bisphosphonates are chemically highly acidic and have a direct irritant effect on the esophageal mucosa. If the pill remains in the esophagus or if there is acid reflux, it can lead to chemical esophagitis, ulceration, and strictures. This is why patients are strictly advised to take the drug on an empty stomach with a full glass of water and remain upright for at least 30 minutes. **Analysis of Incorrect Options:** * **A. Cholelithiasis:** This is not associated with bisphosphonates. It is a common side effect of **Octreotide** (due to inhibition of gallbladder contractility) and **Fibrates**. * **B. Constipation:** While mild GI upset can occur, constipation is not a hallmark side effect. In contrast, **Calcium supplements** (often co-prescribed with bisphosphonates) are a frequent cause of constipation. * **D. Osteonecrosis:** Specifically **Osteonecrosis of the Jaw (ONJ)** is a well-known but **rare** complication, usually seen with high-dose intravenous bisphosphonates (like Zoledronate) used in oncology, rather than routine oral therapy for osteoporosis. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** They are structural analogs of pyrophosphate; they bind to hydroxyapatite in bone and inhibit **osteoclasts** (via inhibition of the farnesyl pyrophosphate synthase enzyme). * **Atypical Fractures:** Long-term use is associated with atypical subtrochanteric femur fractures due to over-suppression of bone turnover. * **Flu-like Syndrome:** Common after the first dose of IV Zoledronate. * **Contraindication:** Do not use in patients with esophageal abnormalities (e.g., achalasia) or severe renal impairment (CrCl <35 mL/min).

Question 290: Insulin release due to closure of K+ channels is seen with which of the following drugs?

A. Nateglinde (Correct Answer)
B. Acarbose
C. Exenatide
D. Sitagliptin

Explanation: **Explanation:** The correct answer is **Nateglinide**. **Mechanism of Action (Correct Option):** Nateglinide belongs to the **Meglitinide** (Glinide) class of oral hypoglycemics. Like Sulfonylureas, Meglitinides act as **insulin secretagogues**. They bind to a specific site on the **ATP-sensitive K+ channel (SUR1 subunit)** on the pancreatic beta-cell membrane. This binding causes the closure of K+ channels, leading to cell depolarization, opening of voltage-gated Ca2+ channels, and subsequent exocytosis of insulin. While they share the same mechanism as Sulfonylureas, Meglitinides have a quicker onset and shorter duration of action, making them ideal for controlling **post-prandial hyperglycemia**. **Analysis of Incorrect Options:** * **B. Acarbose:** An **alpha-glucosidase inhibitor** that acts in the intestinal brush border to delay the digestion and absorption of carbohydrates. It does not affect insulin secretion directly. * **C. Exenatide:** A **GLP-1 receptor agonist** (Incretin mimetic). It stimulates insulin release in a glucose-dependent manner via cAMP signaling, not by direct closure of K+ channels. * **D. Sitagliptin:** A **DPP-4 inhibitor** that prevents the breakdown of endogenous GLP-1 and GIP, thereby indirectly increasing glucose-dependent insulin secretion. **High-Yield Clinical Pearls for NEET-PG:** * **K+ channel blockers:** Sulfonylureas (e.g., Glimepiride) and Meglitinides (Repaglinide, Nateglinide). * **K+ channel openers:** Diazoxide and Minoxidil (can cause hypoglycemia inhibition/hyperglycemia). * **Nateglinide vs. Repaglinide:** Nateglinide is D-phenylalanine derivative; Repaglinide is a benzoic acid derivative. * **Safety:** Meglitinides are safer in patients with sulfur allergies (unlike Sulfonylureas) and carry a lower risk of prolonged hypoglycemia.

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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