Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 181: Which of the following statements about pioglitazone is false?

A. It is a PPARγ agonist.
B. It is metabolized in the liver.
C. It is not given in cases of diastolic dysfunction.
D. It acts on the insulin gene and helps in carbohydrate metabolism even in the absence of insulin. (Correct Answer)

Explanation: **Explanation:** **Why Option D is the Correct (False) Statement:** Pioglitazone belongs to the **Thiazolidinedione (TZD)** class. Its primary mechanism involves binding to the **PPARγ (Peroxisome Proliferator-Activated Receptor gamma)**, a nuclear receptor. This complex then binds to DNA to modulate the transcription of genes involved in glucose and lipid metabolism (e.g., increasing GLUT-4 transporters). Crucially, TZDs are **"insulin sensitizers"**; they reduce insulin resistance in peripheral tissues (muscle, fat, liver). They **cannot** function in the absence of insulin, as their role is to enhance the body's response to existing insulin. **Analysis of Other Options:** * **Option A:** True. PPARγ is the molecular target found predominantly in adipose tissue. * **Option B:** True. Pioglitazone is extensively metabolized in the liver, primarily via CYP2C8 and CYP3A4. * **Option C:** True. TZDs cause fluid retention and plasma volume expansion. Therefore, they are strictly contraindicated in patients with **NYHA Class III or IV heart failure** and are avoided in patients with significant diastolic dysfunction to prevent acute pulmonary edema. **High-Yield Clinical Pearls for NEET-PG:** * **Adverse Effects:** Weight gain, peripheral edema, and increased risk of **bladder cancer** (long-term use). * **Bone Health:** Increased risk of fractures, especially in postmenopausal women, due to diverted mesenchymal stem cell differentiation (away from osteoblasts toward adipocytes). * **Lipid Profile:** Unlike Rosiglitazone, Pioglitazone has a more favorable effect on lipids (decreases triglycerides and increases HDL). * **Monitoring:** While the older TZD (Troglitazone) was hepatotoxic, Pioglitazone still requires baseline liver function tests (LFTs).

Question 182: Cabergoline is the drug of choice for which condition?

A. Parkinsonism
B. Alzheimer's disease
C. Prolactinoma (Correct Answer)
D. Galactorrhea

Explanation: **Explanation:** **Correct Answer: C. Prolactinoma** **Mechanism and Rationale:** Cabergoline is a potent, long-acting **ergot-derived Dopamine (D2) receptor agonist** [1]. In the anterior pituitary, dopamine acts as the primary inhibitory factor for prolactin secretion. By stimulating D2 receptors on lactotrophs, Cabergoline effectively suppresses prolactin synthesis and release. It is considered the **Drug of Choice (DOC)** for prolactinomas because it is more effective at shrinking tumor size and normalizing prolactin levels compared to Bromocriptine, with the added benefit of a better side-effect profile and a longer half-life (allowing for once or twice weekly dosing) [1], [2]. **Analysis of Incorrect Options:** * **A. Parkinsonism:** While dopamine agonists (like Bromocriptine, Pramipexole, or Ropinirole) are used in Parkinson’s, Cabergoline is rarely used today for this indication due to the risk of **cardiac valvular fibrosis** at the high doses required for motor symptoms. * **B. Alzheimer’s Disease:** This condition is characterized by a cholinergic deficit. Treatment involves cholinesterase inhibitors (Donepezil) or NMDA antagonists (Memantine), not dopamine agonists. * **D. Galactorrhea:** While Cabergoline treats galactorrhea, the question asks for the specific clinical *condition*. Galactorrhea is a *symptom* often caused by a prolactinoma. In the context of NEET-PG, always prioritize the definitive pathological diagnosis (Prolactinoma) over the clinical sign. **High-Yield Clinical Pearls for NEET-PG:** * **Half-life:** Cabergoline has a very long half-life (~65 hours), enabling weekly dosing [1]. * **Side Effects:** Nausea and orthostatic hypotension are common. Long-term high-dose use requires monitoring for cardiac valvulopathy via echocardiography [3]. * **Pregnancy:** Bromocriptine is generally preferred if pregnancy is desired due to a longer track record of safety data, though Cabergoline is increasingly used.

Question 183: All of the following statements about nateglinide are true except?

A. Decreases post-prandial hyperglycemia
B. Hypoglycemia is less common than with sulfonylureas
C. It decreases insulin resistance (Correct Answer)
D. It acts by releasing insulin

Explanation: **Explanation:** **Nateglinide** belongs to the **Meglitinide (Glinide)** class of oral hypoglycemic agents. The core mechanism of this class is the stimulation of insulin secretion from the pancreas, making them **insulin secretagogues**, not insulin sensitizers. 1. **Why Option C is the correct answer (False statement):** Nateglinide does **not** decrease insulin resistance. Drugs that decrease insulin resistance (insulin sensitizers) include Biguanides (Metformin) and Thiazolidinediones (Pioglitazone). Nateglinide works solely by increasing the output of insulin from functional pancreatic beta cells. 2. **Analysis of other options:** * **Option A (True):** Nateglinide has a very rapid onset and short duration of action. It is specifically taken just before meals to mimic the first-phase insulin response, effectively controlling **post-prandial hyperglycemia**. * **Option B (True):** Because of its short half-life and "quick-on, quick-off" action, the risk of delayed or prolonged **hypoglycemia is significantly lower** compared to long-acting sulfonylureas (like Glibenclamide). * **Option D (True):** Like sulfonylureas, nateglinide binds to the **SUR1 receptor** on the ATP-sensitive $K^+$ channels of pancreatic $\beta$-cells, causing channel closure, depolarization, $Ca^{2+}$ influx, and subsequent **insulin release**. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Closes ATP-sensitive $K^+$ channels (distinct binding site from sulfonylureas). * **Metabolism:** Primarily metabolized by the liver; it is safer than sulfonylureas in patients with mild-to-moderate renal impairment. * **Dosing:** Known as "post-prandial glucose regulators"; if a meal is skipped, the dose must be skipped to avoid hypoglycemia. * **Weight Gain:** Like all secretagogues, nateglinide can cause modest weight gain.

Question 184: What is the drug of choice for managing hyperglycemia in diabetic ketoacidosis?

A. Regular insulin (Correct Answer)
B. Lente insulin
C. Glyburide
D. 70/30 insulin

Explanation: **Explanation:** **1. Why Regular Insulin is the Correct Answer:** Regular insulin (Short-acting) is the drug of choice for Diabetic Ketoacidosis (DKA) because it is the **only** insulin formulation that can be administered **intravenously (IV)**. In DKA, there is severe dehydration and poor peripheral perfusion, making subcutaneous absorption unpredictable. IV administration ensures 100% bioavailability and a rapid onset of action. Its short half-life (approx. 5–10 minutes when given IV) allows for precise titration based on hourly blood glucose monitoring, minimizing the risk of sudden hypoglycemia or cerebral edema. **2. Why Other Options are Incorrect:** * **Lente insulin:** This is an intermediate-acting insulin. It has a slow onset and prolonged duration, making it unsuitable for the acute, minute-to-minute management required in DKA. * **Glyburide:** This is a second-generation Sulfonylurea (oral hypoglycemic). It works by stimulating pancreatic beta cells to release insulin. In DKA, there is an absolute or relative insulin deficiency and severe metabolic derangement that oral agents cannot correct. * **70/30 insulin:** This is a premixed combination (70% NPH, 30% Regular). Because it contains NPH (intermediate-acting), it cannot be given intravenously and is used for chronic maintenance, not emergencies. **3. High-Yield Clinical Pearls for NEET-PG:** * **Route:** In DKA, Regular insulin is given as a continuous low-dose IV infusion (0.1 units/kg/hour). * **Potassium Warning:** Always check potassium levels before starting insulin. Insulin shifts $K^+$ into cells; if the patient is hypokalemic ($<3.3$ mEq/L), starting insulin can cause fatal arrhythmias. * **The Goal:** The primary goal of insulin in DKA is not just to lower glucose, but to **stop ketogenesis** by inhibiting hormone-sensitive lipase. * **Switching:** Transition to subcutaneous insulin only when the anion gap has closed and the patient is able to eat.

Question 185: All of the following are side effects of steroids except?

A. Hyperglycemia
B. Infection
C. Osteomalacia (Correct Answer)
D. Peptic ulcer

Explanation: **Explanation:** The correct answer is **Osteomalacia** because glucocorticoids (steroids) cause **Osteoporosis**, not osteomalacia. 1. **Why Osteomalacia is incorrect:** Osteomalacia is a defect in bone *mineralization* (soft bones), usually due to Vitamin D deficiency. Steroids, however, cause a decrease in bone *density* (brittle bones) by inhibiting osteoblast activity, stimulating osteoclasts, and decreasing intestinal calcium absorption. This leads to **Osteoporosis** and an increased risk of avascular necrosis of the femoral head. 2. **Analysis of other options:** * **Hyperglycemia:** Steroids are "diabetogenic." They increase gluconeogenesis in the liver and decrease peripheral glucose uptake (insulin resistance), often leading to steroid-induced diabetes. * **Infection:** Steroids are potent immunosuppressants. They inhibit NF-κB, decrease cytokine production (IL-1, IL-2), and cause lymphopenia, masking signs of inflammation and increasing susceptibility to opportunistic infections (e.g., Tuberculosis reactivation). * **Peptic Ulcer:** Steroids inhibit phospholipase A2, reducing protective prostaglandins in the gastric mucosa. When used with NSAIDs, the risk of peptic ulceration and perforation increases significantly. **Clinical Pearls for NEET-PG:** * **Mnemonic for Steroid Side Effects:** "CUSHINGOID" (Cataracts, Ulcers, Striae/Skin thinning, Hypertension, Immunosuppression, Necrosis of femoral head, Glucose elevation, Osteoporosis, Impaired wound healing, Depression/Psychosis). * **Ocular effects:** Steroids cause **posterior subcapsular cataracts** and can increase intraocular pressure (glaucoma). * **Growth:** In children, they cause growth retardation due to premature closure of epiphyseal plates.

Question 186: Which of the following is true about Metformin?

A. Hypoglycemia is very common.
B. Increases hepatic gluconeogenesis.
C. Reduces lipogenesis in adipose tissue. (Correct Answer)
D. Increases the secretion of insulin.

Explanation: **Explanation:** Metformin, a Biguanide, is the first-line oral hypoglycemic agent for Type 2 Diabetes Mellitus. Its primary mechanism involves the activation of **AMP-activated protein kinase (AMPK)**. **Why Option C is Correct:** Activation of AMPK leads to the inhibition of **Acetyl-CoA carboxylase (ACC)**. This results in decreased fatty acid synthesis (**reduced lipogenesis**) and increased fatty acid oxidation. In adipose tissue, this metabolic shift helps improve insulin sensitivity and contributes to the weight-neutral or weight-loss profile of the drug. **Analysis of Incorrect Options:** * **Option A:** Metformin is an **"euglycemic"** agent, not a hypoglycemic one. It does not stimulate insulin release; therefore, the risk of hypoglycemia is negligible when used as monotherapy. * **Option B:** Metformin **decreases** hepatic gluconeogenesis (the primary mechanism for lowering fasting blood glucose) by inhibiting mitochondrial glycerophosphate dehydrogenase (mGPD). * **Option D:** Metformin does not affect the pancreatic beta cells; it **increases peripheral glucose uptake** (sensitizes tissues to existing insulin) rather than increasing insulin secretion. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** First-line for T2DM and Polycystic Ovarian Syndrome (PCOS). * **Side Effects:** Most common are GI-related (diarrhea, abdominal pain). The most dreaded is **Lactic Acidosis** (avoid in renal failure, CrCl <30 ml/min). * **Vitamin Deficiency:** Long-term use can lead to **Vitamin B12 deficiency** due to interference with its absorption in the terminal ileum. * **Pleiotropic Effect:** It is associated with a reduced risk of certain cancers and cardiovascular mortality.

Question 187: Which of the following is an irreversible aromatase inhibitor?

A. Anastrozole
B. Exemestane (Correct Answer)
C. Letrozole
D. Vorozole

Explanation: ### Explanation **Aromatase inhibitors (AIs)** are a class of drugs used primarily in the treatment of hormone-responsive breast cancer in postmenopausal women. They work by blocking the enzyme **aromatase**, which converts androgens (androstenedione and testosterone) into estrogens (estrone and estradiol). #### Why Exemestane is Correct Aromatase inhibitors are classified into two types based on their chemical structure and mechanism of action: 1. **Type I Inhibitors (Steroidal):** These are structural analogues of androstenedione. They bind **irreversibly** (covalently) to the active site of the enzyme, causing permanent inactivation. This is often referred to as "suicide inhibition." **Exemestane** and Formestane belong to this group. 2. **Type II Inhibitors (Non-steroidal):** These bind **reversibly** to the heme moiety of the cytochrome P450 unit of the enzyme. **Anastrozole, Letrozole, and Vorozole** belong to this group. #### Analysis of Incorrect Options * **A. Anastrozole:** A potent, third-generation non-steroidal AI. It binds reversibly and is a first-line treatment for postmenopausal breast cancer. * **C. Letrozole:** Similar to Anastrozole, it is a reversible, non-steroidal AI. It is also frequently used for ovulation induction in PCOS (off-label). * **D. Vorozole:** A non-steroidal, reversible AI that is less commonly used in clinical practice compared to Letrozole or Anastrozole. #### NEET-PG High-Yield Pearls * **Indication:** AIs are only effective in **postmenopausal** women because they cannot inhibit the high levels of aromatase produced by functioning ovaries in premenopausal women. * **Side Effects:** Unlike Tamoxifen (a SERM), AIs do not increase the risk of endometrial cancer or venous thromboembolism. However, they significantly increase the risk of **osteoporosis and bone fractures** due to profound estrogen deprivation. * **Letrozole vs. Clomiphene:** Letrozole is now often preferred over Clomiphene for ovulation induction in PCOS because it has a lower risk of multiple pregnancies and no anti-estrogenic effect on the endometrium.

Question 188: Which among the following is not an androgen receptor blocker?

A. Finasteride (Correct Answer)
B. Cyproterone
C. Flutamide
D. None of the above

Explanation: **Explanation:** The correct answer is **Finasteride** because it is not an androgen receptor blocker; rather, it is a **5-alpha reductase inhibitor**. **1. Why Finasteride is the correct answer:** Finasteride works by inhibiting the enzyme 5-alpha reductase (specifically Type II), which converts Testosterone into its more potent metabolite, **Dihydrotestosterone (DHT)**. It does not bind to or block the androgen receptor itself. It is primarily used in the treatment of Benign Prostatic Hyperplasia (BPH) and Male Pattern Baldness (Androgenetic Alopecia). **2. Why the other options are incorrect:** * **Cyproterone:** This is a steroidal anti-androgen that acts as a competitive antagonist at the androgen receptor. It also has progestational activity, which suppresses LH secretion, further reducing testosterone levels. * **Flutamide:** This is a non-steroidal (pure) anti-androgen that competitively blocks androgen receptors. It is frequently used in the management of metastatic prostatic carcinoma. **High-Yield NEET-PG Pearls:** * **Dutasteride:** Unlike Finasteride, Dutasteride inhibits both Type I and Type II 5-alpha reductase. * **Bicalutamide & Enzalutamide:** Newer non-steroidal anti-androgens preferred over Flutamide due to better safety profiles (lower hepatotoxicity). * **Spironolactone:** Primarily a potassium-sparing diuretic, but also acts as a weak androgen receptor blocker, often used clinically for hirsutism in females. * **Side Effects:** Finasteride can cause erectile dysfunction and decreased libido due to reduced DHT levels. Cyproterone can cause hepatotoxicity and gynecomastia.

Question 189: Which insulin has a late onset of action, longer duration of action, and no pronounced peak?

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

Explanation: ### Explanation **Correct Option: C. Glargine** Insulin Glargine is a **long-acting basal insulin analog**. Its unique pharmacokinetic profile is due to its chemical structure: the addition of two arginine residues and the substitution of glycine. * **Mechanism:** It is soluble at an acidic pH (4.0) but **precipitates** into micro-crystals upon subcutaneous injection (neutral pH). These crystals dissolve slowly, resulting in a steady, slow release into the bloodstream. * **Profile:** This provides a "peakless" (flat) concentration curve, a late onset (1–2 hours), and a long duration of action (up to 24 hours), mimicking the natural basal secretion of the pancreas. **Incorrect Options:** * **A. NPH (Neutral Protamine Hagedorn):** An intermediate-acting insulin. Unlike Glargine, it has a **distinct peak** (4–10 hours) and a shorter duration (12–18 hours), which increases the risk of nocturnal hypoglycemia. * **B. Glulisine & D. Aspart:** These are **rapid-acting insulin analogs**. They have a very fast onset (5–15 mins), a sharp peak (1 hour), and a short duration (3–5 hours). They are used specifically for postprandial (mealtime) glucose control. **NEET-PG High-Yield Pearls:** 1. **Basal Insulins:** Glargine, Detemir, and Degludec. **Degludec** has the longest half-life (>40 hours). 2. **Mixing:** Glargine should **not** be mixed in the same syringe with other insulins because its acidic pH can cause the other insulin to precipitate. 3. **Safety:** Because Glargine is peakless, it carries a significantly **lower risk of nocturnal hypoglycemia** compared to NPH. 4. **Rapid-acting Mnemonic:** "No **LAG**" (**L**ispro, **A**spart, **G**lulisine).

Question 190: Antithyroid drugs are indicated in which of the following conditions, except?

A. Graves' disease
B. Toxic nodular goiter
C. Along with radioactive iodine
D. Prophylaxis of endemic goiter (Correct Answer)

Explanation: **Explanation:** The primary goal of **Antithyroid Drugs (ATDs)** like Methimazole, Carbimazole, and Propylthiouracil (PTU) is to inhibit the synthesis of thyroid hormones by blocking the enzyme thyroid peroxidase. **Why Option D is the Correct Answer:** **Endemic goiter** is primarily caused by **iodine deficiency**, leading to low T3/T4 levels and a compensatory rise in TSH, which causes thyroid enlargement. Treating or preventing this condition with antithyroid drugs is contraindicated because ATDs further decrease hormone synthesis, which would worsen the hypothyroidism and exacerbate the goiter. The correct management for endemic goiter is **Iodine supplementation** (e.g., iodized salt). **Analysis of Incorrect Options:** * **A. Graves' Disease:** This is an autoimmune condition causing hyperthyroidism. ATDs are the first-line medical management to achieve remission. * **B. Toxic Nodular Goiter:** Characterized by hyperfunctioning nodules. While surgery or radioiodine is often definitive, ATDs are used to control thyrotoxic symptoms and render the patient euthyroid before surgery. * **C. Along with Radioactive Iodine (RAI):** ATDs are used **before** RAI to deplete thyroid hormone stores (preventing a thyroid storm post-radiation) and **after** RAI to maintain euthyroidism until the radiation effect fully manifests (which can take 3–6 months). **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Methimazole is generally preferred over PTU due to its longer half-life and lower hepatotoxicity. * **Pregnancy:** **PTU** is preferred in the **1st trimester** (less teratogenic; Methimazole causes *Aplasia Cutis*). **Methimazole** is preferred in the **2nd and 3rd trimesters** (to avoid PTU-induced hepatotoxicity). * **Most Serious Side Effect:** **Agranulocytosis** (presents as fever and sore throat); requires immediate discontinuation of the drug.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

Insulin and Oral Hypoglycemic Agents

Practice Questions

Adrenocorticosteroids

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Sex Hormones: Estrogens and Progestins

Practice Questions

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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