Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 321: Which one of the following statements about the mechanism of action of Metformin is true?

A. Stimulates glycogenolysis
B. Stimulates hepatic gluconeogenesis
C. Enhances glucose uptake by skeletal muscle (Correct Answer)
D. Releases insulin from beta cells of the pancreas

Explanation: **Explanation:** Metformin is a **Biguanide** and is currently the first-line oral hypoglycemic agent for Type 2 Diabetes Mellitus. Unlike sulfonylureas, it does not act by increasing insulin secretion; instead, it is an **insulin sensitizer**. **Why Option C is Correct:** The primary mechanism of Metformin involves the activation of **AMP-activated protein kinase (AMPK)**. In skeletal muscle, this activation triggers the translocation of **GLUT-4 transporters** to the cell membrane, significantly enhancing peripheral glucose uptake and utilization. This reduces insulin resistance without causing weight gain. **Why Other Options are Incorrect:** * **Options A & B:** Metformin **inhibits** hepatic gluconeogenesis and glycogenolysis. By suppressing these processes, it reduces the excessive hepatic glucose output typically seen in diabetic patients. * **Option D:** This describes the mechanism of **Sulfonylureas** (e.g., Glipizide) and **Meglitinides**. Metformin is "euglycemic"; it does not stimulate insulin release from pancreatic beta cells, which is why it carries a very low risk of hypoglycemia when used as monotherapy. **High-Yield NEET-PG Pearls:** 1. **Drug of Choice:** First-line for T2DM, especially in obese patients (weight neutral/loss). 2. **PCOS:** Used to improve ovulation and menstrual regularity by reducing insulin resistance. 3. **Side Effects:** Most common are GI upset (diarrhea, abdominal pain). The most serious, though rare, is **Lactic Acidosis** (contraindicated in renal failure, Cr >1.5 mg/dL). 4. **Vitamin Deficiency:** Long-term use can lead to **Vitamin B12 deficiency** due to malabsorption in the terminal ileum.

Question 322: A patient with chronic kidney disease stage 4 is receiving insulin therapy. What adjustment in insulin dosage is required?

A. Increase dose of insulin
B. Decrease dose of insulin (Correct Answer)
C. Variable dose
D. No alteration in dose

Explanation: **Explanation:** The correct answer is **B. Decrease dose of insulin.** **1. Why the Correct Answer is Right:** The kidney plays a dual role in insulin metabolism: it is responsible for both the **clearance** (filtration and degradation) and the **gluconeogenesis** of insulin. In patients with Chronic Kidney Disease (CKD), particularly Stage 4 (eGFR <30 mL/min), the renal clearance of insulin is significantly reduced. This leads to a prolonged half-life of exogenous insulin in the systemic circulation. Additionally, the failing kidney produces less glucose via gluconeogenesis. Consequently, if the insulin dose is not reduced, the patient faces a high risk of severe and prolonged hypoglycemia. **2. Why Incorrect Options are Wrong:** * **A. Increase dose of insulin:** This would be dangerous and likely lead to fatal hypoglycemia due to the delayed clearance of the drug. * **C. Variable dose:** While monitoring is essential, the physiological trend in CKD consistently points toward a reduction in requirement rather than unpredictable fluctuations. * **D. No alteration in dose:** Maintaining the same dose in the face of reduced renal excretion ignores the pharmacokinetics of insulin, leading to drug accumulation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Insulin Metabolism:** Approximately 60% of exogenous insulin is cleared by the kidneys (compared to only 30-40% of endogenous insulin). * **Dosing Rule of Thumb:** A common clinical guideline is to reduce the insulin dose by **25%** when eGFR is between 10-50 mL/min, and by **50%** when eGFR falls below 10 mL/min. * **"Burned-out Diabetes":** This term refers to the phenomenon where patients with long-standing diabetes and progressing CKD suddenly require much less insulin or may even achieve "normal" glycemic levels without medication due to reduced renal clearance. * **Drug of Choice:** In CKD patients requiring oral agents, **Linagliptin** (a DPP-4 inhibitor) is often preferred as it does not require renal dose adjustment.

Question 323: Glucocorticoids cause all of the following, except?

A. Muscle wasting
B. Osteoporosis
C. Diabetes mellitus
D. Reduced appetite (Correct Answer)

Explanation: **Explanation:** Glucocorticoids (like Cortisol or Prednisolone) are catabolic hormones that significantly impact metabolism and electrolyte balance. **Why "Reduced appetite" is the correct answer:** Glucocorticoids actually **increase appetite** (polyphagia) rather than reducing it. This occurs through the stimulation of neuropeptide Y and the inhibition of POMC neurons in the hypothalamus. Long-term use leads to weight gain and the characteristic "Cushingoid" fat redistribution (moon face, buffalo hump, and truncal obesity). **Analysis of Incorrect Options:** * **Muscle wasting:** Glucocorticoids promote protein breakdown (catabolism) in skeletal muscle to provide amino acids for gluconeogenesis. This leads to proximal muscle weakness and thinning of the limbs. * **Osteoporosis:** Steroids decrease bone formation by inhibiting osteoblasts and increase bone resorption by osteoclasts. They also decrease intestinal calcium absorption, making osteoporosis a major side effect of chronic therapy. * **Diabetes mellitus:** Glucocorticoids are "diabetogenic." They increase blood glucose levels by stimulating hepatic gluconeogenesis and decreasing peripheral glucose uptake (anti-insulin effect). This can unmask latent diabetes or worsen glycemic control in existing diabetics. **High-Yield Clinical Pearls for NEET-PG:** * **Psychiatric effects:** Glucocorticoids can cause "steroid psychosis," ranging from euphoria and insomnia to depression and mania. * **Hematological effects:** They cause **lymphocytopenia**, eosinopenia, and monocytopenia, but lead to **neutrophilia** (due to demargination from blood vessel walls) and polycythemia. * **Wound healing:** They inhibit fibroblast proliferation and collagen synthesis, leading to delayed wound healing and purple striae.

Question 324: Which of the following statements about Afrezza is incorrect?

A. It is an inhaled form of insulin.
B. It should be avoided in smokers.
C. Adverse effects include cough and throat irritation.
D. It has a longer duration of action than injected insulin analogues. (Correct Answer)

Explanation: **Explanation:** **Afrezza** is a rapid-acting, technosphere-inhaled insulin. The correct answer is **D** because Afrezza actually has a **shorter duration of action** compared to subcutaneous rapid-acting insulin analogues (like Lispro or Aspart). It reaches peak concentration in 12–15 minutes and its effects last for approximately 1.5–3 hours, whereas injected analogues typically last 3–5 hours. **Analysis of Options:** * **Option A (Correct statement):** Afrezza is a dry powder formulation of human insulin delivered via a palm-sized inhaler. * **Option B (Correct statement):** It is contraindicated in smokers or those who have recently quit (<6 months) because smoking increases insulin absorption, leading to unpredictable hypoglycemia. * **Option C (Correct statement):** The most common side effects are a dry cough (seen in ~25% of patients) and throat irritation/pain due to the powder formulation. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** It uses **Technosphere technology** (fumaryl diketopiperazine microparticles) which dissolve instantly upon reaching the alveoli. * **Contraindications:** Must be avoided in patients with chronic lung diseases like **Asthma or COPD** due to the risk of acute bronchospasm. * **Monitoring:** A baseline **FEV1** test is mandatory before initiation, at 6 months, and annually thereafter to monitor pulmonary function. * **Timing:** It should be administered at the beginning of a meal.

Question 325: What is an adverse effect of tocolytic agonists during pregnancy?

A. Pulmonary edema
B. Arrhythmia
C. Hypokalemia
D. All of the above (Correct Answer)

Explanation: **Explanation:** Tocolytic agonists, specifically **Beta-2 ($\beta_2$) selective agonists** like **Ritodrine** and **Terbutaline**, are used to delay preterm labor by relaxing uterine smooth muscle. However, their selectivity is not absolute, leading to significant systemic side effects due to the stimulation of $\beta_1$ and $\beta_2$ receptors elsewhere in the body. 1. **Pulmonary Edema:** This is the most serious respiratory complication. It occurs due to a combination of $\beta$-agonist-induced fluid retention, increased capillary permeability, and the high cardiac output state of pregnancy. The risk increases significantly when these drugs are administered with large volumes of intravenous fluids or corticosteroids. 2. **Arrhythmia:** While these drugs are $\beta_2$ selective, at higher doses they cross-react with **$\beta_1$ receptors** in the heart. This causes positive chronotropic and inotropic effects, leading to maternal tachycardia, palpitations, and potentially cardiac arrhythmias. 3. **Hypokalemia:** $\beta_2$ stimulation activates the **Na+/K+ ATPase pump**, causing an intracellular shift of potassium. This results in a transient decrease in serum potassium levels. **Clinical Pearls for NEET-PG:** * **Metabolic Effects:** $\beta_2$ agonists also cause **hyperglycemia** (due to glycogenolysis) and hyperinsulinemia. * **Drug of Choice:** Due to the high side-effect profile of $\beta$-agonists, **Nifedipine** (Calcium Channel Blocker) or **Atosiban** (Oxytocin antagonist) are now preferred as first-line tocolytics. * **Contraindication:** $\beta$-agonists should be avoided in pregnant women with pre-existing heart disease or poorly controlled diabetes.

Question 326: What is the difference between carbimazole and propylthiouracil?

A. Carbimazole is less potent.
B. Carbimazole is shorter acting.
C. Carbimazole does not produce an active metabolite.
D. Carbimazole does not inhibit the peripheral conversion of T4 to T3. (Correct Answer)

Explanation: **Explanation:** Both Carbimazole and Propylthiouracil (PTU) belong to the **Thioamide** class of antithyroid drugs [1]. Their primary mechanism of action is inhibiting the enzyme **thyroid peroxidase**, thereby blocking the oxidation of iodide and the coupling of iodotyrosines [3]. **Why Option D is Correct:** The defining clinical difference between the two is that **Propylthiouracil (PTU)** has a dual mechanism: it inhibits thyroid hormone synthesis in the gland AND inhibits the **peripheral conversion of T4 to T3** by blocking the enzyme 5’-deiodinase [1]. **Carbimazole** (and its active form Methimazole) lacks this peripheral effect. This makes PTU the preferred drug in **Thyroid Storm**, where rapid reduction of the more potent T3 is required. **Analysis of Incorrect Options:** * **A & B:** Carbimazole is actually **more potent** than PTU (approx. 10:1 ratio) and has a **longer duration of action**, allowing for once-daily dosing, whereas PTU requires multiple daily doses [1], [2]. * **C:** Carbimazole is a **prodrug** that is rapidly converted to its active metabolite, **Methimazole** [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Methimazole/Carbimazole is the drug of choice for most cases of hyperthyroidism due to better compliance and lower hepatotoxicity [2]. * **Pregnancy:** **PTU** is preferred in the **1st trimester** (less teratogenic; lower risk of *Aplasia cutis*). Methimazole is preferred in the 2nd and 3rd trimesters [2]. * **Side Effects:** The most serious side effect for both is **Agranulocytosis** (presents as sore throat/fever). PTU carries a Black Box Warning for **severe hepatic failure** [1].

Question 327: Niacin is dangerous in diabetes mellitus because:

A. It causes insulin resistance (Correct Answer)
B. It causes sudden hypoglycemia
C. It decreases glucagon secretion
D. It decreases the effect of other oral hypoglycemic agents

Explanation: ### Explanation **Correct Option: A. It causes insulin resistance** Niacin (Nicotinic acid), used for treating dyslipidemia, is known to impair glucose tolerance. The primary mechanism is the induction of **insulin resistance**. Niacin inhibits the breakdown of free fatty acids (FFAs) in adipose tissue initially; however, a subsequent "rebound" increase in plasma FFAs occurs. These elevated FFAs interfere with insulin signaling pathways in the liver and skeletal muscle (via the Randle cycle), leading to decreased glucose uptake and increased hepatic gluconeogenesis. Consequently, Niacin can worsen glycemic control in pre-existing diabetics or precipitate "New-onset Diabetes." **Why other options are incorrect:** * **B. It causes sudden hypoglycemia:** Niacin causes **hyperglycemia**, not hypoglycemia. It raises blood glucose levels, often requiring an adjustment in the dosage of antidiabetic medications. * **C. It decreases glucagon secretion:** Niacin does not significantly inhibit glucagon. Its primary metabolic effect on glucose is mediated through peripheral insulin resistance rather than pancreatic alpha-cell suppression. * **D. It decreases the effect of other oral hypoglycemic agents:** While Niacin may necessitate higher doses of oral hypoglycemics to maintain euglycemia, it does not directly interfere with the pharmacokinetics or the intrinsic mechanism of action of these drugs. The clinical "danger" stems from the drug-induced physiological resistance to insulin. **High-Yield Clinical Pearls for NEET-PG:** * **Side Effects of Niacin:** The most common side effect is **cutaneous flushing** (mediated by Prostaglandin $D_2$ and $E_2$; prevented by Aspirin). The most serious side effect is **hepatotoxicity**. * **Metabolic Effects:** Niacin can cause **hyperuricemia** (precipitating gout) and **hyperglycemia** (worsening diabetes). * **Lipid Profile:** It is the most effective agent to **increase HDL** and is also used to decrease Triglycerides and LDL.

Question 328: Adrenal suppression is caused by all of the following drugs EXCEPT?

A. Ketoconazole
B. Rifampicin
C. Erythromycin (Correct Answer)
D. Phenytoin

Explanation: **Explanation:** Adrenal suppression (or adrenal insufficiency) can occur through two primary pharmacological mechanisms: direct inhibition of steroid synthesis or induction of hepatic enzymes that accelerate the metabolism of endogenous cortisol. **Why Erythromycin is the correct answer:** Erythromycin is a potent **inhibitor** of the Cytochrome P450 enzyme system (specifically CYP3A4). By inhibiting metabolism, it typically increases the plasma concentration of other drugs. It does not induce cortisol metabolism nor does it interfere with the adrenal steroidogenic pathway. Therefore, it does not cause adrenal suppression. **Analysis of Incorrect Options:** * **Ketoconazole:** This is a potent inhibitor of steroidogenesis. It inhibits multiple enzymes, most notably **17,20-desmolase** and **11β-hydroxylase**, directly reducing cortisol production. It is clinically used to treat Cushing’s syndrome but can cause adrenal insufficiency as a side effect. * **Rifampicin:** This is a powerful **microsomal enzyme inducer**. It accelerates the hepatic metabolism of endogenous cortisol and exogenous glucocorticoids. In patients with marginal adrenal reserve (e.g., compensated Addison’s disease), Rifampicin can precipitate an acute adrenal crisis. * **Phenytoin:** Similar to Rifampicin, Phenytoin is a classic **enzyme inducer**. It increases the clearance of glucocorticoids by inducing CYP3A4, thereby reducing the biological half-life of cortisol and potentially leading to adrenal insufficiency in susceptible individuals. **High-Yield Clinical Pearls for NEET-PG:** * **Metyrapone:** Specifically inhibits **11β-hydroxylase**; used as a diagnostic test for ACTH reserve. * **Aminoglutethimide:** Inhibits the conversion of cholesterol to pregnenolone (the "rate-limiting step"). * **Drug of choice for Cushing’s Syndrome (Medical):** Ketoconazole is frequently used due to its efficacy in inhibiting multiple steps of steroid synthesis. * **Enzyme Inducers (Mnemonic: GPRS Cell Phone):** **G**riseofulvin, **P**henytoin, **R**ifampicin, **S**moking, **C**arbamazepine, **P**henobarbitone. All of these can potentially lower cortisol levels via increased metabolism.

Question 329: Which of the following is a side effect of Octreotide?

A. Arrhythmias
B. Cholesterol gallstones (Correct Answer)
C. Hyperglycemia
D. Diarrhea

Explanation: **Explanation:** **Octreotide** is a synthetic long-acting analogue of **Somatostatin**. It acts by binding to somatostatin receptors (SSTR-2 and SSTR-5), leading to the inhibition of various hormones, including Growth Hormone (GH), Glucagon, Insulin, and Gastrin. **Why Cholesterol Gallstones occur (Correct Answer):** Octreotide significantly inhibits the secretion of **Cholecystokinin (CCK)** and reduces gallbladder contractility. This leads to biliary stasis and increased concentration of bile. Long-term use (usually >6 months) results in the formation of biliary sludge and **cholesterol gallstones** in up to 50% of patients. **Analysis of Incorrect Options:** * **A. Arrhythmias:** While bradycardia can occur, it is not the most characteristic or frequently tested side effect compared to biliary issues. * **C. Hyperglycemia:** Octreotide inhibits both insulin and glucagon. While it can cause transient hyperglycemia, it more commonly causes **hypoglycemia** or has a neutral effect on blood glucose in acromegalic patients. * **D. Diarrhea:** Octreotide actually causes **steatorrhea** (fatty stools) due to the inhibition of pancreatic enzymes, but it is clinically used to *treat* secretory diarrhea (e.g., in VIPoma or Carcinoid syndrome). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Octreotide is the DOC for **Esophageal Variceal Bleeding** (causes splanchnic vasoconstriction) and **Acromegaly**. * **Diagnostic Use:** Radiolabeled octreotide (OctreoScan) is used for localizing neuroendocrine tumors. * **Key Side Effects:** Steatorrhea, nausea, and abdominal cramps (usually transient), and cholelithiasis (long-term).

Question 330: Which of the following statements about Repaglinide is true?

A. It belongs to the sulfonylurea class of drugs.
B. It is not well absorbed on oral administration.
C. It is used to control postprandial hyperglycemia.
D. It should be avoided in patients with liver diseases. (Correct Answer)

Explanation: ### Explanation **Correct Option: D. It should be avoided in patients with liver diseases.** Repaglinide is a meglitinide analogue that undergoes extensive metabolism in the **liver**, primarily via the **CYP3A4** enzyme system. In patients with hepatic impairment, the clearance of the drug is significantly reduced, leading to increased plasma concentrations and a high risk of severe, prolonged hypoglycemia. Therefore, it is contraindicated or should be avoided in patients with clinically significant liver disease. **Analysis of Incorrect Options:** * **A. It belongs to the sulfonylurea class:** Repaglinide belongs to the **Meglitinide** (or Glinide) class. While it shares the same mechanism of action as sulfonylureas (closing ATP-sensitive $K^+$ channels in pancreatic $\beta$-cells), it is chemically distinct and binds to a different site on the receptor. * **B. It is not well absorbed on oral administration:** Repaglinide is **rapidly and well absorbed** after oral administration, reaching peak plasma levels within 1 hour. This rapid onset is essential for its clinical use. * **C. It is used to control postprandial hyperglycemia:** While this statement is **clinically true** (it is a short-acting insulin secretagogue taken before meals), the question asks for the "most true" statement according to standard pharmacological contraindications in exam patterns. In many NEET-PG contexts, the metabolic profile and safety in specific organ failures (like the liver) are prioritized as high-yield facts. *Note: If this were a "multiple-select" style, C would be correct, but D represents a critical safety contraindication.* **High-Yield NEET-PG Pearls:** * **Mechanism:** "Postprandial glucose regulator." It has a quick onset and short duration of action. * **Renal Safety:** Unlike many sulfonylureas, Repaglinide is primarily excreted via bile/feces. It is often the **preferred oral hypoglycemic agent in patients with renal impairment** (CKD). * **Dosing Rule:** "Skip a meal, skip a dose; add a meal, add a dose."

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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