Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 31: Which of the following are the adverse effects of pioglitazone?

A. Weight gain
B. Hepatotoxicity
C. Increased risk of urinary bladder cancer
D. All of the above (Correct Answer)

Explanation: **Explanation:** Pioglitazone belongs to the **Thiazolidinedione (TZD)** class of antidiabetic drugs. It acts as a selective agonist for the nuclear receptor **PPAR-γ** (peroxisome proliferator-activated receptor gamma), which enhances insulin sensitivity in peripheral tissues. **Analysis of Options:** * **Weight Gain:** This is a classic side effect of TZDs. It occurs due to a combination of fluid retention (edema) and the differentiation of pre-adipocytes into mature adipocytes, leading to increased subcutaneous fat storage. * **Hepatotoxicity:** While the first drug in this class, Troglitazone, was withdrawn due to severe liver failure, Pioglitazone still carries a risk of idiosyncratic hepatotoxicity. Periodic monitoring of liver function tests (LFTs) is clinically recommended. * **Bladder Cancer:** Long-term use (typically >1 year) of Pioglitazone has been linked to an increased risk of urinary bladder cancer. Consequently, it is contraindicated in patients with active bladder cancer or a history of the disease. **Clinical Pearls for NEET-PG:** 1. **Fluid Retention:** TZDs cause sodium and water reabsorption in the collecting ducts. Therefore, they are **contraindicated in NYHA Class III and IV Heart Failure.** 2. **Fracture Risk:** Pioglitazone is associated with decreased bone mineral density and an increased risk of **distal upper and lower limb fractures**, especially in women. 3. **Lipid Profile:** Unlike Rosiglitazone, Pioglitazone has a more favorable effect on lipids, often decreasing triglycerides and increasing HDL. 4. **Mechanism:** Remember "PPAR-γ" for TZDs vs. "PPAR-α" for Fibrates.

Question 32: Triiodothyronine (T3) as compared to Thyroxine (T4):

A. Is more plasma protein bound
B. Is shorter acting (Correct Answer)
C. Is less potent
D. Has delayed action

Explanation: To understand the differences between **Triiodothyronine (T3)** and **Thyroxine (T4)**, one must look at their binding affinity and metabolic clearance. ### **Explanation of the Correct Answer** **Option B (Is shorter acting) is correct.** T3 has a much lower affinity for plasma proteins (specifically Thyroid Binding Globulin) compared to T4. Because more T3 exists in the "free" active form, it is metabolized and cleared by the body much faster. The half-life of **T3 is approximately 1 day**, whereas the half-life of **T4 is about 7 days**. Consequently, T3 has a shorter duration of action. ### **Why the Other Options are Incorrect** * **A. Is more plasma protein bound:** Incorrect. T4 is 99.9% bound, while T3 is about 99.7% bound. Though the difference seems small, the 10-fold higher concentration of "free" T3 significantly impacts its kinetics. * **C. Is less potent:** Incorrect. T3 is **3 to 5 times more potent** than T4. T3 is the biologically active form that binds to the nuclear thyroid receptor; T4 acts largely as a pro-hormone. * **D. Has delayed action:** Incorrect. Because T3 does not need to be deiodinated (unlike T4) and binds directly to receptors, it has a **rapid onset of action** compared to the lag period seen with T4. ### **NEET-PG High-Yield Pearls** * **Drug of Choice:** Levothyroxine (T4) is the drug of choice for hypothyroidism due to its long half-life (once-daily dosing) and stable blood levels. * **Myxedema Coma:** Liothyronine (T3) is preferred in emergencies due to its rapid onset of action. * **Peripheral Conversion:** T4 is converted to T3 in peripheral tissues by the enzyme **5'-deiodinase**. This conversion is inhibited by **Propylthiouracil (PTU), Propranolol, and Glucocorticoids**—a favorite fact for MCQ examiners. * **Reverse T3 (rT3):** An inactive isomer formed during periods of starvation or severe illness (Euthyroid Sick Syndrome).

Question 33: Which of the following agents is a dual agonist for both PPAR-α and PPAR-γ receptors?

A. Pioglitazone
B. Fenofibrate
C. Beroglitazar (Correct Answer)
D. Bromocriptine

Explanation: **Explanation:** **Correct Answer: C. Beroglitazar** **Mechanism and Concept:** Beroglitazar belongs to a newer class of drugs known as **Glitazars** (Dual PPAR agonists). These agents act as agonists at both **PPAR-α** (Peroxisome Proliferator-Activated Receptor-alpha) and **PPAR-γ** (gamma) receptors. * **PPAR-α activation:** Leads to a reduction in triglycerides and an increase in HDL (similar to fibrates). * **PPAR-γ activation:** Enhances insulin sensitivity in peripheral tissues (similar to thiazolidinediones). By targeting both receptors, Glitazars aim to treat the "dyslipidemic triad" and insulin resistance simultaneously in patients with Type 2 Diabetes Mellitus. Other examples include Saroglitazar (the first to be approved in India). **Analysis of Incorrect Options:** * **A. Pioglitazone:** This is a pure **PPAR-γ agonist** (Thiazolidinedione). While it has some minor PPAR-α effects compared to Rosiglitazone, it is primarily classified as a PPAR-γ agonist used for insulin sensitization. * **B. Fenofibrate:** This is a fibric acid derivative that acts as a selective **PPAR-α agonist**. Its primary clinical use is the reduction of high triglyceride levels. * **C. Bromocriptine:** This is a **Dopamine (D2) receptor agonist**. A specific quick-release formulation is FDA-approved for Type 2 Diabetes, but its mechanism involves modulating circadian hypothalamic dopamine activity, not PPAR receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Saroglitazar:** The first dual PPAR agonist approved (in India) specifically for diabetic dyslipidemia and Non-Alcoholic Steatohepatitis (NASH). * **PPAR-γ** is associated with side effects like weight gain, edema, and increased risk of bone fractures. * **PPAR-δ (delta):** Some newer experimental agents (Pan-PPAR agonists) target alpha, gamma, and delta receptors.

Question 34: Which of the following is a long-acting glucocorticoid?

A. Dexamethasone (Correct Answer)
B. Triamcinolone
C. Prednisolone
D. Hydrocortisone

Explanation: **Explanation:** Glucocorticoids are classified based on their duration of action (biological half-life), which correlates with their anti-inflammatory potency and mineralocorticoid (salt-retaining) activity. **1. Why Dexamethasone is correct:** **Dexamethasone** (along with Betamethasone) is a **long-acting glucocorticoid** with a biological half-life of **36–54 hours**. It is highly potent (about 25–30 times more potent than hydrocortisone) and possesses negligible mineralocorticoid activity, making it ideal for conditions where fluid retention must be avoided, such as cerebral edema. **2. Why the other options are incorrect:** * **Hydrocortisone (Option D):** This is a **short-acting** glucocorticoid (half-life 8–12 hours). It is the pharmaceutical form of endogenous cortisol and has significant mineralocorticoid activity (1:1 ratio), making it the drug of choice for replacement therapy in adrenal insufficiency. * **Prednisolone (Option C):** This is an **intermediate-acting** glucocorticoid (half-life 18–36 hours). It is 4 times more potent than hydrocortisone and is commonly used for long-term systemic therapy in autoimmune and inflammatory conditions. * **Triamcinolone (Option B):** Also an **intermediate-acting** steroid. It has slightly higher anti-inflammatory potency than prednisolone but zero mineralocorticoid activity. **High-Yield NEET-PG Pearls:** * **Potency Rule:** As the duration of action increases, anti-inflammatory potency increases, while mineralocorticoid activity decreases. * **Dexamethasone Suppression Test (DST):** Used to diagnose Cushing’s syndrome. * **Fetal Lung Maturity:** Betamethasone or Dexamethasone are used in preterm labor because they cross the placenta and have low protein binding. * **Drug of Choice for Addisonian Crisis:** Intravenous Hydrocortisone.

Question 35: What is the drug of choice for hyperthyroidism in pregnancy?

A. Methimazole
B. Carbimazole
C. Propylthiouracil (Correct Answer)
D. I-131

Explanation: **Explanation:** The management of hyperthyroidism in pregnancy is a high-yield topic focused on balancing maternal health with fetal safety. **1. Why Propylthiouracil (PTU) is the Correct Answer:** PTU is the drug of choice during the **first trimester** of pregnancy. The primary reason is its pharmacological profile: it is highly protein-bound and less lipid-soluble compared to Methimazole. Consequently, it crosses the placenta less readily. More importantly, PTU is not associated with the specific congenital malformations (embryopathy) linked to Methimazole. **2. Analysis of Incorrect Options:** * **Methimazole (A) & Carbimazole (B):** These are avoided in the first trimester because they are associated with **Methimazole Embryopathy**, which includes **Aplasia Cutis** (congenital absence of skin, usually on the scalp), esophageal atresia, and choanal atresia. Carbimazole is a prodrug that is converted to Methimazole in the body. * **I-131 (D):** Radioactive iodine is **absolutely contraindicated** in pregnancy. It crosses the placenta and can cause permanent destruction of the fetal thyroid gland, leading to congenital hypothyroidism. **3. Clinical Pearls for NEET-PG:** * **The "Switch" Strategy:** Current guidelines recommend **PTU for the 1st Trimester**, then switching to **Methimazole for the 2nd and 3rd Trimesters**. This is because PTU carries a higher risk of maternal hepatotoxicity, while the risk of Methimazole embryopathy passes after the first 10 weeks of gestation. * **Mechanism of Action:** Both drugs inhibit Thyroid Peroxidase (TPO), but **PTU** has the additional advantage of inhibiting the peripheral conversion of T4 to T3. * **Breastfeeding:** Both PTU and Methimazole are considered safe during breastfeeding at moderate doses.

Question 36: Lactic acidosis is a common adverse effect of which class of antidiabetic medications?

A. Metformin
B. Phenformin (Correct Answer)
C. Repaglinide
D. Rosiglitazone

Explanation: **Phenformin** belongs to the Biguanide class of antidiabetics. It was withdrawn from the market globally because it significantly increases the risk of **lactic acidosis**. Biguanides inhibit mitochondrial oxidation of lactate and promote anaerobic glycolysis [1]. Phenformin has a high affinity for mitochondrial membranes and a long half-life, leading to a much higher incidence of lactic acidosis (approx. 40–60 cases per 100,000 patient-years) compared to Metformin. **Analysis of Options:** * **A. Metformin:** While also a Biguanide, Metformin has a much lower risk of lactic acidosis (approx. 3 cases per 100,000). It is the first-line drug for Type 2 Diabetes. It only poses a significant risk in patients with severe renal impairment (eGFR <30 ml/min), where the drug accumulates [1]. * **C. Repaglinide:** This is a Meglitinide (K+ ATP channel blocker). Its primary side effect is hypoglycemia and weight gain, not lactic acidosis. * **D. Rosiglitazone:** This is a Thiazolidinedione (PPAR-γ agonist). Its major adverse effects include fluid retention, weight gain, congestive heart failure, and increased risk of bone fractures [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Biguanides:** Activation of AMP-activated protein kinase (AMPK), leading to decreased hepatic gluconeogenesis and increased peripheral glucose uptake [1]. * **Metformin Contraindication:** Should be withheld before and 48 hours after using **IV contrast** to prevent acute kidney injury and subsequent lactic acidosis. * **Drug of Choice:** Metformin remains the drug of choice for obese Type 2 Diabetics as it is "weight neutral" and does not cause hypoglycemia (euglycemic agent).

Question 37: All of the following preparations of insulin are rapid and short-acting EXCEPT:

A. Lispro
B. Aspart
C. Glargine (Correct Answer)
D. NPH

Explanation: ### Explanation Insulin preparations are classified based on their onset and duration of action. To answer this question, one must distinguish between **bolus (prandial)** insulins and **basal** insulins. **1. Why Glargine is the Correct Answer:** **Insulin Glargine** is a **long-acting (basal) insulin analog**. It is designed to have low solubility at physiological pH; once injected subcutaneously, it precipitates into micro-crystals that are slowly absorbed into the bloodstream. This results in a "peakless" profile with a duration of action lasting approximately 24 hours. Therefore, it is neither rapid nor short-acting. **2. Analysis of Other Options:** * **Lispro & Aspart (Options A & B):** These are **Rapid-acting insulin analogs**. By modifying the amino acid sequence of the insulin B-chain, these drugs prevent the formation of hexamers, allowing for immediate dissociation into monomers. They have an onset of 5–15 minutes and are used to control postprandial glucose. * **NPH (Option D):** Neutral Protamine Hagedorn (NPH) is an **Intermediate-acting insulin**. While it is not "rapid-acting," the question asks to identify the exception among preparations that are typically grouped as short/rapid versus long-acting. In many clinical classifications, NPH is contrasted against long-acting analogs like Glargine because NPH has a distinct peak and shorter duration (12–18 hours). However, in the context of this specific MCQ, Glargine is the definitive "long-acting" outlier. **3. NEET-PG High-Yield Clinical Pearls:** * **Ultra-Rapid Acting:** Lispro, Aspart, Glulisine (Mnemonic: **L**og **A**ll **G**lucose). * **Long-Acting (Peakless):** Glargine, Detemir, Degludec. * **Site of Injection:** Absorption is fastest in the **Abdomen**, followed by the arm, thigh, and buttock. * **Mechanism of Glargine:** Substitution of glycine at A21 and addition of two arginines at the B-chain C-terminus. * **Drug of Choice:** Insulin is the drug of choice for diabetes in pregnancy and during emergency management of Diabetic Ketoacidosis (Regular Insulin IV).

Question 38: Which of the following is a long-acting insulin?

A. Lente
B. Semilente
C. Ultralente (Correct Answer)
D. Lispro insulin

Explanation: **Explanation:** Insulin preparations are classified based on their onset and duration of action. Understanding this classification is high-yield for NEET-PG, as it dictates the clinical use of insulin in "basal-bolus" regimens. **Correct Option: C. Ultralente** Ultralente is a **long-acting** crystalline insulin suspension. It has a slow onset and a prolonged duration of action (up to 24–36 hours). It was traditionally used to provide basal insulin coverage, though it has largely been replaced in modern practice by peakless analogues like Glargine and Detemir. **Analysis of Incorrect Options:** * **A. Lente:** This is an **intermediate-acting** insulin. It is a mixture consisting of 30% Semilente (rapid/short) and 70% Ultralente (long-acting), resulting in an intermediate profile. * **B. Semilente:** This is a **short-acting** insulin (amorphous insulin precipitation). It has a quicker onset than Lente but a shorter duration of action. * **D. Lispro:** This is an **ultra-rapid-acting** insulin analogue. It is designed to be taken immediately before meals to control postprandial glucose spikes due to its very fast onset (15 mins) and short duration (3–5 hours). **High-Yield Clinical Pearls for NEET-PG:** 1. **Rapid-acting analogues:** Lispro, Aspart, Glulisine (Mnemonic: *"No **LAG** in action"*). 2. **Long-acting analogues:** Glargine, Detemir, Degludec. 3. **Degludec** is the longest-acting insulin (duration >42 hours). 4. **Glargine** is known as "peakless" insulin, reducing the risk of nocturnal hypoglycemia. 5. **Regular Insulin** is the only form that can be administered intravenously (used in Diabetic Ketoacidosis).

Question 39: Glibenclamide reduces blood glucose in all of the following EXCEPT:

A. Non-diabetics
B. Type 1 diabetics (Correct Answer)
C. Type 2 diabetics
D. Obese diabetics

Explanation: **Explanation:** The correct answer is **Type 1 diabetics** because of the specific mechanism of action of Sulfonylureas. **Mechanism of Action:** Glibenclamide is a second-generation sulfonylurea. It works by binding to the **SUR1 subunit** of the ATP-sensitive potassium channels ($K_{ATP}$) on the pancreatic **beta-cells**. This leads to channel closure, cell depolarization, calcium influx, and the subsequent release of **endogenous insulin**. 1. **Why Type 1 Diabetics is the correct answer:** Type 1 Diabetes Mellitus is characterized by the autoimmune destruction of pancreatic beta-cells, leading to an **absolute insulin deficiency**. Since Glibenclamide requires functional beta-cells to stimulate insulin release, it is ineffective in Type 1 patients. 2. **Why other options are incorrect:** * **Non-diabetics:** In healthy individuals, beta-cells are functional. Glibenclamide will trigger insulin release, potentially causing profound hypoglycemia. * **Type 2 diabetics:** These patients have relative insulin deficiency and insulin resistance but retain some beta-cell function, making them the primary candidates for this drug. * **Obese diabetics:** Most obese diabetics have Type 2 DM. While metformin is the preferred first-line agent due to weight neutrality, sulfonylureas still effectively reduce blood glucose in these patients. **NEET-PG High-Yield Pearls:** * **Primary Failure:** When sulfonylureas fail to work from the start (often due to misdiagnosed Type 1 DM or LADA). * **Secondary Failure:** When the drug loses efficacy over years due to progressive beta-cell exhaustion. * **Side Effects:** Hypoglycemia (most common) and weight gain. * **Drug Interaction:** Glibenclamide is metabolized by CYP2C9; drugs like sulfonamides can displace it from plasma proteins, increasing hypoglycemia risk.

Question 40: A widely used drug that suppresses cellular immunity inhibits prostaglandin and leukotriene synthesis and increases the catabolism of IgG antibody is:

A. Cyclophosphamide
B. Prednisone (Correct Answer)
C. Cyclosporine
D. Infliximab

Explanation: **Explanation:** The correct answer is **Prednisone**, a synthetic glucocorticoid. Its mechanism of action is multifaceted, involving the modulation of gene expression via intracellular receptors. 1. **Mechanism of Correct Option:** * **Suppression of Cellular Immunity:** Prednisone inhibits the production of IL-2 and other cytokines, leading to decreased T-cell proliferation. * **Inhibition of Eicosanoids:** It induces **Lipocortin (Annexin A1)**, which inhibits the enzyme **Phospholipase A2**. This prevents the release of arachidonic acid, thereby blocking both the **Cyclooxygenase (COX)** and **Lipoxygenase (LOX)** pathways, effectively inhibiting both prostaglandins and leukotrienes. * **IgG Catabolism:** Glucocorticoids are unique in their ability to increase the rate of IgG degradation, reducing the half-life of these antibodies. 2. **Analysis of Incorrect Options:** * **Cyclophosphamide (A):** An alkylating agent that cross-links DNA. While it suppresses immunity, it does not directly inhibit the synthesis of prostaglandins or leukotrienes. * **Cyclosporine (C):** A calcineurin inhibitor that specifically inhibits IL-2 production. It does not affect the phospholipase A2 pathway or increase IgG catabolism. * **Infliximab (D):** A monoclonal antibody against TNF-α. It has a very specific target and does not possess the broad metabolic or eicosanoid-inhibiting effects of steroids. **NEET-PG High-Yield Pearls:** * **Glucocorticoids** are the only drugs that inhibit both COX and LOX pathways by acting upstream on Phospholipase A2. * They cause **lymphocytopenia** (by redistributing T-cells to bone marrow) but cause **neutrophilia** (by decreasing marginalization of neutrophils). * **Metabolic effects:** They are catabolic in nature (except in the liver), leading to muscle wasting, osteoporosis, and hyperglycemia.

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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