Endocrine Pharmacology — MCQs
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If a patient with hyperglycemia is given IV insulin, which of the following can occur?
A 47-year-old male presented with signs and symptoms of acromegaly. Radiologic studies showed the presence of a large pituitary tumor. Surgical treatment of the tumor was only partially effective in controlling the disease. At this point, which of the following drugs is most likely to be used as pharmacological therapy?
What is the mechanism of action of oral hypoglycemic agents?
Which of the following statements about diazoxide is false?
A pregnant female with thyrotoxicosis is planned for surgery. Before surgery can be done, her gland should be reduced in size and vascularity by administering which of the following?
Which of the following drugs is a Selective Estrogen Receptor Modulator (SERM) useful for the treatment of osteoporosis?
A patient with Addison's disease presented with adrenal crisis. What is the drug of choice?
What is the drug of choice for the management of hypertension in a patient with pheochromocytoma?
Which of the following has more anti-thyroid action?
What is the corticosteroid of choice in acute adrenal insufficiency?
Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs
Question 201: If a patient with hyperglycemia is given IV insulin, which of the following can occur?
- A. Hypokalemia (Correct Answer)
- B. Hyperkalemia
- C. Hyponatremia
- D. Hypernatremia
Explanation: The correct answer is **Hypokalemia (Option A)**. **Mechanism:** Insulin plays a critical role in electrolyte balance by stimulating the **Na⁺/K⁺-ATPase pump** located on the membranes of skeletal muscle and liver cells. When IV insulin is administered, it increases the activity of this pump, leading to an influx of potassium ions from the extracellular fluid (ECF) into the intracellular fluid (ICF) [2]. This shift results in a rapid decrease in serum potassium levels, potentially causing hypokalemia [3]. This effect occurs independently of insulin’s glucose-lowering action. **Analysis of Incorrect Options:** * **B. Hyperkalemia:** This is the opposite of the physiological effect of insulin. However, hyperkalemia is often seen in untreated Diabetic Ketoacidosis (DKA) due to insulin deficiency and acidosis [4]; insulin therapy is used specifically to *reverse* this. * **C & D. Hyponatremia/Hypernatremia:** While insulin affects the Na⁺/K⁺ pump, its primary and most immediate clinical impact is on potassium. Changes in sodium levels in hyperglycemic states are usually secondary to osmotic shifts (dilutional hyponatremia) rather than a direct effect of insulin administration [4]. **NEET-PG High-Yield Pearls:** * **Clinical Application:** Because insulin shifts potassium intracellularly, a combination of **IV Insulin and Dextrose** is a standard emergency treatment for **Hyperkalemia** [3]. * **DKA Management:** In patients with Diabetic Ketoacidosis, serum potassium may appear normal or high, but total body potassium is depleted. Starting insulin can cause a precipitous drop in K⁺; therefore, potassium supplementation is often required even if initial levels are within the normal range [1]. * **Other drugs causing K⁺ shift:** Beta-2 agonists (e.g., Salbutamol) also stimulate the Na⁺/K⁺-ATPase pump and can cause hypokalemia.
Question 202: A 47-year-old male presented with signs and symptoms of acromegaly. Radiologic studies showed the presence of a large pituitary tumor. Surgical treatment of the tumor was only partially effective in controlling the disease. At this point, which of the following drugs is most likely to be used as pharmacological therapy?
- A. Desmopressin
- B. Leuprolide
- C. Octreotide (Correct Answer)
- D. Somatropin
Explanation: ### Explanation **Correct Answer: C. Octreotide** **Mechanism and Rationale:** Acromegaly is caused by the excessive secretion of **Growth Hormone (GH)**, usually due to a pituitary adenoma [1]. When surgery is incomplete or contraindicated, pharmacological management is required. **Octreotide** is a potent synthetic analog of **Somatostatin** (Growth Hormone Inhibiting Hormone) [1]. It has a much longer half-life than natural somatostatin and works by binding to somatostatin receptors (primarily SSTR-2 and SSTR-5) on the pituitary tumor, thereby inhibiting the secretion of GH and reducing levels of Insulin-like Growth Factor-1 (IGF-1) [2]. **Analysis of Incorrect Options:** * **A. Desmopressin:** A synthetic analog of Vasopressin (ADH). It is used in the treatment of Central Diabetes Insipidus and nocturnal enuresis, but has no role in GH regulation. * **B. Leuprolide:** A GnRH agonist. It is used to treat prostate cancer, endometriosis, and precocious puberty by suppressing the pituitary-gonadal axis. It does not affect GH secretion. * **D. Somatropin:** This is recombinant human Growth Hormone. It is used to treat GH deficiency (dwarfism). Administering it to an acromegalic patient would worsen the clinical condition. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Transsphenoidal surgery is the primary treatment for acromegaly. Octreotide (or Lanreotide) is the medical treatment of choice for persistent disease [1]. * **Side Effects of Octreotide:** The most characteristic side effect is the formation of **biliary sludge or gallstones** (due to inhibition of cholecystokinin and gallbladder contractility) and steatorrhea [1]. * **Alternative Therapy:** **Pegvisomant** is a GH-receptor antagonist used in resistant cases [3]. **Pasireotide** is a newer somatostatin analog with higher affinity for SSTR-5 [2]. * **Monitoring:** Serum **IGF-1 levels** are the most reliable marker for monitoring disease activity and treatment response in acromegaly [3].
Question 203: What is the mechanism of action of oral hypoglycemic agents?
- A. Inhibit glucose uptake by skeletal muscle
- B. Enhance glucose uptake by skeletal muscle (Correct Answer)
- C. Stimulate glycogenolysis
- D. Stimulate gluconeogenesis
Explanation: **Explanation:** The primary goal of oral hypoglycemic agents (OHAs) is to reduce blood glucose levels in patients with Type 2 Diabetes Mellitus. **Why Option B is Correct:** Several classes of OHAs work by increasing the utilization of glucose in peripheral tissues. Specifically, **Biguanides (Metformin)** and **Thiazolidinediones (Pioglitazone)** act as insulin sensitizers. Metformin activates AMP-activated protein kinase (AMPK), which promotes the translocation of **GLUT-4 transporters** to the cell membranes of skeletal muscle. This directly **enhances glucose uptake** and utilization, thereby lowering plasma glucose levels. **Why the Other Options are Incorrect:** * **Option A:** Inhibiting glucose uptake would lead to hyperglycemia, worsening the diabetic state. * **Option C & D:** Glycogenolysis (breakdown of glycogen to glucose) and Gluconeogenesis (synthesis of glucose from non-carbohydrate sources) are processes that increase blood sugar. OHAs like Metformin actually **inhibit** these hepatic processes to prevent fasting hyperglycemia. **NEET-PG High-Yield Pearls:** * **Metformin** is the first-line drug for T2DM; it does not cause hypoglycemia (euglycemic) or weight gain. * **SGLT-2 Inhibitors (Dapagliflozin):** Act on the proximal tubule to cause glucosuria. * **Sulfonylureas (Glimepiride):** Act by closing ATP-sensitive K+ channels in pancreatic beta cells, leading to insulin secretion. * **DPP-4 Inhibitors (Sitagliptin):** Prevent the breakdown of GLP-1, enhancing glucose-dependent insulin secretion.
Question 204: Which of the following statements about diazoxide is false?
- A. It acts by causing prolonged opening of ATP-dependent potassium channels in beta cells.
- B. It can cause severe hypoglycemia. (Correct Answer)
- C. It can be used to treat patients with insulinoma.
- D. It is used as an antihypertensive agent.
Explanation: **Explanation:** **Diazoxide** is a non-diuretic thiazide derivative that acts as a **potassium channel opener**. 1. **Why Option B is the correct answer (False statement):** Diazoxide does not cause hypoglycemia; rather, it causes **hyperglycemia**. By opening ATP-sensitive $K^+$ channels in the pancreatic beta cells, it hyperpolarizes the cell membrane. This prevents the influx of calcium and inhibits the release of insulin. Therefore, it is used to *treat* hypoglycemia, not cause it. 2. **Analysis of other options:** * **Option A (True):** Its primary mechanism of action is the prolonged opening of ATP-dependent $K^+$ channels, which stabilizes the resting membrane potential and prevents depolarization. * **Option C (True):** Because it inhibits insulin secretion, it is a first-line medical management for patients with **insulinoma** (insulin-secreting tumors) or leucine-sensitive hypoglycemia. * **Option D (True):** Diazoxide also opens $K^+$ channels in vascular smooth muscle, leading to vasodilation. While rarely used today due to newer agents, it was historically used as an intravenous bolus for **hypertensive emergencies**. **NEET-PG High-Yield Pearls:** * **Side Effects:** The most characteristic side effect of chronic diazoxide use is **hypertrichosis** (excessive hair growth), similar to Minoxidil. It can also cause salt and water retention. * **Contrast with Sulfonylureas:** While Sulfonylureas *close* $K_{ATP}$ channels to stimulate insulin, Diazoxide *opens* them to inhibit insulin. * **Clinical Use:** Primarily used for persistent hyperinsulinemic hypoglycemia of infancy (PHHI) and inoperable insulinomas.
Question 205: A pregnant female with thyrotoxicosis is planned for surgery. Before surgery can be done, her gland should be reduced in size and vascularity by administering which of the following?
- A. Iodide ion
- B. Propranolol
- C. Propylthiouracil (Correct Answer)
- D. Radioactive iodine
Explanation: ### Explanation **Correct Option: C. Propylthiouracil (PTU)** In a pregnant patient with thyrotoxicosis requiring surgery, the primary goal is to achieve a **euthyroid state** before the procedure to prevent a thyroid storm. **Propylthiouracil (PTU)** is the drug of choice during the **first trimester** of pregnancy. It inhibits the enzyme thyroid peroxidase (blocking thyroid hormone synthesis) and, crucially, inhibits the peripheral conversion of T4 to the more active T3. While PTU itself does not directly reduce vascularity, it is the standard medical optimization therapy in pregnancy to stabilize the patient before surgical intervention. **Analysis of Incorrect Options:** * **A. Iodide ion (Lugol’s Iodine/SSKI):** While iodides are classically used pre-operatively to decrease the size and vascularity of the thyroid gland (via the Wolff-Chaikoff effect), they are generally **avoided in pregnancy**. Prolonged use can cross the placenta and cause **fetal goiter** and hypothyroidism. * **B. Propranolol:** This is used for symptomatic control (tachycardia, tremors) but does not affect the synthesis of thyroid hormones or the physical characteristics (size/vascularity) of the gland itself. * **D. Radioactive Iodine (I-131):** This is **absolutely contraindicated** in pregnancy as it crosses the placenta and destroys the fetal thyroid gland, leading to permanent cretinism. **High-Yield NEET-PG Pearls:** * **Drug of Choice (DOC):** PTU is preferred in the **1st trimester** (due to Methimazole's association with *Aplasia Cutis* and *Choanal Atresia*). Methimazole is preferred in the **2nd and 3rd trimesters** to avoid PTU-induced hepatotoxicity. * **Pre-op Goal:** In non-pregnant patients, the combination of an antithyroid drug (to achieve euthyroidism) followed by Iodides (10 days pre-op to reduce vascularity) is standard. In pregnancy, we rely primarily on antithyroid drugs. * **Surgery Timing:** If surgery is necessary during pregnancy, the **second trimester** is the safest period.
Question 206: Which of the following drugs is a Selective Estrogen Receptor Modulator (SERM) useful for the treatment of osteoporosis?
- A. Raloxifene (Correct Answer)
- B. Bisphosphonate
- C. Strontium
- D. Estradiol
Explanation: **Explanation:** **1. Why Raloxifene is Correct:** Raloxifene is a **Selective Estrogen Receptor Modulator (SERM)**. Its clinical utility stems from its unique tissue-specific action: it acts as an **estrogen agonist in the bone**, where it inhibits osteoclast activity and increases bone mineral density, making it effective for preventing and treating postmenopausal osteoporosis. Crucially, it acts as an **estrogen antagonist in the breast and uterus**, thereby reducing the risk of breast cancer and avoiding the risk of endometrial hyperplasia associated with traditional Hormone Replacement Therapy (HRT). **2. Analysis of Incorrect Options:** * **B. Bisphosphonates (e.g., Alendronate):** While these are the first-line drugs for osteoporosis, they are not SERMs. They work by inhibiting the enzyme farnesyl pyrophosphate synthase in osteoclasts, leading to osteoclast apoptosis. * **C. Strontium (Strontium Ranelate):** This is a divalent cation that has a dual action (increasing bone formation and decreasing resorption), but it is not a SERM. * **D. Estradiol:** This is a natural estrogen. While it prevents bone loss, it is not "selective." It stimulates estrogen receptors in the breast and endometrium, increasing the risk of cancer, and is therefore not classified as a SERM. **3. NEET-PG High-Yield Pearls:** * **Raloxifene vs. Tamoxifen:** Tamoxifen is a SERM used for breast cancer; unlike Raloxifene, Tamoxifen is an agonist in the uterus (increasing risk of endometrial cancer). **Raloxifene is an antagonist in the uterus.** * **Adverse Effect:** The most significant side effect of Raloxifene is an increased risk of **Venous Thromboembolism (VTE)** and hot flashes. * **Bazedoxifene:** Another SERM used in combination with conjugated estrogens for osteoporosis and vasomotor symptoms.
Question 207: A patient with Addison's disease presented with adrenal crisis. What is the drug of choice?
- A. Hydrocortisone (Correct Answer)
- B. Betamethasone
- C. Dexamethasone
- D. Prednisolone
Explanation: **Explanation:** **Adrenal crisis** (acute adrenal insufficiency) is a life-threatening emergency characterized by a severe deficiency of both glucocorticoids and mineralocorticoids. **Why Hydrocortisone is the Drug of Choice:** Hydrocortisone (intravenous) is the preferred treatment because it possesses **equal glucocorticoid and mineralocorticoid activity** (ratio 1:1). In an acute crisis, the patient requires immediate replacement of cortisol to handle stress and aldosterone to correct life-threatening hyponatremia, hyperkalemia, and hypotension. Hydrocortisone’s rapid onset of action and balanced profile make it the gold standard for stabilizing the hemodynamic status of the patient. **Why the other options are incorrect:** * **Betamethasone & Dexamethasone:** These are highly potent, long-acting **pure glucocorticoids**. They have negligible mineralocorticoid activity. While they are potent anti-inflammatory agents, they fail to correct the electrolyte imbalances and fluid loss associated with mineralocorticoid deficiency in Addisonian crisis. * **Prednisolone:** This is an intermediate-acting steroid with predominant glucocorticoid activity and only minimal mineralocorticoid effect. It is more suitable for chronic maintenance therapy rather than acute emergency management. **High-Yield Clinical Pearls for NEET-PG:** * **Management Protocol:** Immediate IV bolus of 100 mg Hydrocortisone, followed by 100–200 mg over 24 hours, along with aggressive IV fluid resuscitation (Normal Saline). * **Maintenance Therapy:** In chronic Addison’s disease, oral Hydrocortisone is used for glucocorticoid effects, while **Fludrocortisone** is added specifically for mineralocorticoid replacement. * **Diagnostic Test:** The **ACTH Stimulation Test** (Cosyntropin test) is the definitive investigation for diagnosing adrenal insufficiency. * **Steroid Potency:** Dexamethasone is the most potent (25–30x more than hydrocortisone), but lacks salt-retaining properties.
Question 208: What is the drug of choice for the management of hypertension in a patient with pheochromocytoma?
- A. Phenoxybenzamine (Correct Answer)
- B. Phentolamine
- C. Labetalol
- D. Esmolol
Explanation: Pheochromocytoma is a catecholamine-secreting tumor (epinephrine and norepinephrine) that causes severe hypertension via excessive stimulation of alpha-1 receptors [2]. **Phenoxybenzamine** is the drug of choice for preoperative management because it is an **irreversible, non-competitive, non-selective alpha-blocker** [1, 2]. Its irreversible nature ensures that even if there is a massive surge of catecholamines (e.g., during surgical manipulation of the tumor), the receptors remain blocked, preventing a hypertensive crisis [1, 2]. It is typically started 10–14 days before surgery to allow for blood pressure control and expansion of the contracted intravascular volume [1, 3]. **2. Why the Other Options are Incorrect:** * **Phentolamine:** While it is a non-selective alpha-blocker, it is **reversible and competitive**. * **Labetalol:** Although it has both alpha and beta-blocking properties, the **beta-to-alpha blockade ratio is high (approx. 3:1)**. Using it as monotherapy can lead to "unopposed alpha stimulation," causing a paradoxical rise in blood pressure [1]. * **Esmolol:** This is a short-acting beta-1 selective blocker. Beta-blockers should **never** be used alone in pheochromocytoma; they must only be introduced *after* adequate alpha-blockade is established to prevent hypertensive crisis [1]. **3. NEET-PG Clinical Pearls:** * **The Golden Rule:** Always "Alpha before Beta." Start alpha-blockers first, then add beta-blockers (usually 2-3 days later) to manage tachycardia [1]. * **Rule of 10s:** Pheochromocytoma is 10% bilateral, 10% malignant, 10% pediatric, 10% extra-adrenal (Paraganglioma), and 10% familial. * **Metyrosine:** An adjuvant drug that inhibits *Tyrosine Hydroxylase* (the rate-limiting enzyme in catecholamine synthesis), used in inoperable or malignant cases.
Question 209: Which of the following has more anti-thyroid action?
- A. I131 (Correct Answer)
- B. Sodium iodide
- C. Carbimazole
- D. Neomercazole
Explanation: The question asks for the agent with the most potent or definitive anti-thyroid action among the choices. **1. Why I131 is the Correct Answer:** Radioactive Iodine (**I¹³¹**) provides the most definitive anti-thyroid action because it causes **permanent destruction** of the thyroid parenchyma [1]. It is trapped by the thyroid gland and incorporated into the follicles. It emits **beta particles** (with a range of 0.5–2 mm), which induce pyknosis and necrosis of the follicular cells followed by fibrosis [1]. Unlike thioamides, which only inhibit hormone synthesis, I¹³¹ results in a "medical thyroidectomy," making it the most potent anti-thyroid intervention listed [2]. **2. Why the Other Options are Incorrect:** * **Sodium Iodide (Stable Iodine):** While high doses of stable iodine (Lugol’s iodine) inhibit the release of thyroid hormones (**Wolff-Chaikoff effect**), the effect is transient (10–14 days) due to the "escape" phenomenon [3],[5]. It is used for preoperative preparation, not definitive therapy [3]. * **Carbimazole:** This is a pro-drug of Methimazole [4]. It belongs to the **Thioamide** class, which acts by inhibiting the enzyme **Thyroid Peroxidase (TPO)**. It prevents the synthesis of new hormones but does not destroy existing thyroid tissue or stop the release of pre-formed hormones [2]. * **Neomercazole:** This is simply a brand name for Carbimazole. Therefore, it carries the same limitations as Option C. **3. NEET-PG High-Yield Pearls:** * **Mechanism of I¹³¹:** Primarily **Beta-ray** emission (90% destruction) and **Gamma-ray** emission (used for scanning) [1]. * **Contraindications for I¹³¹:** Pregnancy (crosses placenta and destroys fetal thyroid) and breastfeeding. * **Drug of Choice:** Methimazole is the DOC for most hyperthyroidism cases except in the **1st trimester of pregnancy**, where **Propylthiouracil (PTU)** is preferred due to lower teratogenicity (avoiding *aplasia cutis*) [4]. * **Iodide's fastest action:** Stable iodides are the fastest-acting anti-thyroid drugs, making them useful in thyroid storms, but they are not the "most" potent in terms of long-term action [3].
Question 210: What is the corticosteroid of choice in acute adrenal insufficiency?
- A. Fludrocortisone
- B. Hydrocortisone (Correct Answer)
- C. Dexamethasone
- D. Prednisolone
Explanation: **Explanation:** **1. Why Hydrocortisone is the Correct Choice:** In acute adrenal insufficiency (Addisonian Crisis), there is a life-threatening deficiency of both **glucocorticoids** and **mineralocorticoids**. Hydrocortisone is the drug of choice because it possesses significant activity in both categories (Glucocorticoid:Mineralocorticoid potency ratio of 1:1). Its rapid onset of action when given intravenously and its ability to mimic the body’s natural cortisol profile make it ideal for stabilizing hemodynamics and correcting electrolyte imbalances (hyponatremia and hyperkalemia) simultaneously. **2. Why Other Options are Incorrect:** * **Fludrocortisone (A):** This is a potent mineralocorticoid. While essential for long-term maintenance of Addison’s disease, it is not used in acute crises because it lacks sufficient glucocorticoid activity and is only available orally. * **Dexamethasone (C):** This is a highly potent, long-acting pure glucocorticoid with **zero mineralocorticoid activity**. While it can be used initially if the diagnosis is uncertain (as it does not interfere with serum cortisol assays), it fails to address the mineralocorticoid deficiency required for long-term stabilization. * **Prednisolone (D):** This has intermediate potency and some mineralocorticoid activity, but it is less effective than hydrocortisone for rapid emergency resuscitation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Management Protocol:** The immediate treatment for adrenal crisis is **IV Hydrocortisone (100mg bolus)** followed by 100–200mg over 24 hours, along with aggressive **Normal Saline (0.9% NaCl)** rehydration. * **Diagnostic Tip:** Dexamethasone is the only steroid that **does not cross-react** with cortisol immunoassays, allowing for a dynamic ACTH stimulation test while the patient is being treated. * **Maintenance:** Once the patient is stable, fludrocortisone is added only when the daily hydrocortisone dose is tapered below 50mg.
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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