Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 371: Which of the following drugs is an antiandrogen?

A. Cyproterone acetate (Correct Answer)
B. Clomiphene citrate
C. Letrozole
D. None of the above

Explanation: **Explanation:** **Cyproterone acetate** is a potent **androgen receptor antagonist** and a progestational agent. It works by competitively inhibiting the binding of dihydrotestosterone (DHT) to its specific receptors in target organs. Additionally, it exerts a negative feedback effect on the hypothalamus and pituitary, reducing the secretion of gonadotropins (LH and FSH), which further lowers testosterone levels. **Analysis of Options:** * **Cyproterone acetate (Correct):** Used clinically in the management of hirsutism in women, precocious puberty in boys, and as palliative treatment for advanced prostatic carcinoma. * **Clomiphene citrate (Incorrect):** This is a **Selective Estrogen Receptor Modulator (SERM)**. It acts as an antagonist at the hypothalamus, blocking the negative feedback of estrogen, which leads to increased FSH/LH secretion. It is primarily used for ovulation induction in infertility. * **Letrozole (Incorrect):** This is a **Third-generation Aromatase Inhibitor**. It prevents the conversion of androgens to estrogens. It is used as a first-line treatment for postmenopausal breast cancer and for ovulation induction. **High-Yield Clinical Pearls for NEET-PG:** * **Flutamide & Bicalutamide:** Pure non-steroidal antiandrogens used primarily for prostatic carcinoma to prevent the "testosterone flare" caused by GnRH agonists. * **Finasteride:** A 5-alpha reductase inhibitor (blocks conversion of Testosterone to DHT); used for Benign Prostatic Hyperplasia (BPH) and male pattern baldness. * **Spironolactone:** A diuretic that also possesses significant antiandrogenic activity, often used off-label for female acne and hirsutism. * **Side Effect:** A common side effect of antiandrogens in males is **gynecomastia**.

Question 372: Which of the following antidiabetic drugs causes weight loss?

A. Metformin (Correct Answer)
B. Sulfonylureas
C. Insulin
D. Nateglinide

Explanation: **Explanation:** The effect of antidiabetic medications on body weight is a high-yield topic for NEET-PG. **Correct Option: A (Metformin)** Metformin, a Biguanide, is considered **weight-neutral or weight-reducing**. It causes weight loss primarily through: 1. **Decreased Appetite:** It increases the release of Glucagon-like peptide-1 (GLP-1) and lactate, which suppress the hunger centers in the hypothalamus. 2. **Gastrointestinal Side Effects:** Common adverse effects like nausea and abdominal discomfort often lead to reduced caloric intake. 3. **Metabolic Effects:** It improves insulin sensitivity and reduces hepatic gluconeogenesis without stimulating insulin secretion (avoiding the anabolic effects of insulin). **Incorrect Options:** * **B. Sulfonylureas (e.g., Glipizide):** These are "insulin secretagogues." By increasing endogenous insulin levels, they promote lipogenesis and glucose uptake into adipose tissue, leading to significant **weight gain**. * **C. Insulin:** Insulin is a potent anabolic hormone. It promotes fat storage and inhibits lipolysis, consistently causing **weight gain** in patients with diabetes. * **D. Nateglinide:** As a Meglitinide analog, it also stimulates insulin secretion (though with a shorter duration than sulfonylureas). Consequently, it is associated with **weight gain**. **High-Yield Clinical Pearls for NEET-PG:** * **Weight Loss Drugs:** Metformin, GLP-1 agonists (Liraglutide, Semaglutide), and SGLT-2 inhibitors (Dapagliflozin). * **Weight Gain Drugs:** Insulin, Sulfonylureas, Thiazolidinediones (Pioglitazone - due to fluid retention and adipogenesis), and Meglitinides. * **Metformin** is the first-line drug for Type 2 Diabetes, especially in obese patients, due to its weight-favorable profile and euglycemic nature (low risk of hypoglycemia).

Question 373: Which antidiabetic medication is known to cause pancreatitis as an adverse drug reaction?

A. Vildagliptin (Correct Answer)
B. Metformin
C. Glibenclamide
D. Insulin

Explanation: **Explanation:** **Vildagliptin** is a **Dipeptidyl Peptidase-4 (DPP-4) inhibitor** (Gliptin). The association between DPP-4 inhibitors and **acute pancreatitis** is a well-documented adverse drug reaction (ADR). The underlying mechanism is thought to involve the chronic stimulation of pancreatic ductal synthesis and hyperplasia induced by increased GLP-1 levels, which can lead to ductal occlusion and subsequent inflammation. Patients starting on "gliptins" should be monitored for persistent, severe abdominal pain. **Analysis of Incorrect Options:** * **Metformin (Biguanide):** Its most notorious life-threatening ADR is **lactic acidosis**. Common side effects are gastrointestinal (diarrhea, abdominal cramps) and Vitamin B12 deficiency. It does not cause pancreatitis. * **Glibenclamide (Sulfonylurea):** The primary adverse effects are **hypoglycemia** and weight gain. It works by stimulating insulin release from pancreatic beta cells but is not associated with pancreatic inflammation. * **Insulin:** The most common ADR is **hypoglycemia**. Other effects include lipodystrophy at the injection site and weight gain. It is actually used in the management of diabetic ketoacidosis, which can sometimes coexist with pancreatitis, but it does not cause the condition. **High-Yield Clinical Pearls for NEET-PG:** 1. **Incretin-based therapies:** Both **DPP-4 inhibitors** (e.g., Vildagliptin, Sitagliptin) and **GLP-1 agonists** (e.g., Exenatide, Liraglutide) are associated with a risk of acute pancreatitis. 2. **Vildagliptin specific:** Unlike Sitagliptin, Vildagliptin has also been associated with **hepatotoxicity**; hence, LFTs should be monitored. 3. **DPP-4 Inhibitor Safety:** **Linagliptin** is the "gliptin" of choice in patients with renal failure as it is primarily excreted via the bile.

Question 374: Which of the following is recombinant PTH?

A. Teriparatide (Correct Answer)
B. Cinacalcet
C. Carisoprodol
D. Oxethazaine

Explanation: **Explanation:** **Teriparatide (Option A)** is the correct answer. It is a **recombinant human parathyroid hormone (rhPTH 1-34)**, consisting of the first 34 amino acids of the natural hormone. While continuous high levels of PTH cause bone resorption, **intermittent (once-daily) subcutaneous administration** of Teriparatide stimulates osteoblastic activity more than osteoclastic activity. This leads to a net increase in bone mineral density, making it a potent anabolic agent for treating severe osteoporosis. **Analysis of Incorrect Options:** * **Cinacalcet (Option B):** It is a **calcimimetic** drug. It increases the sensitivity of calcium-sensing receptors (CaSR) in the parathyroid gland to extracellular calcium, thereby inhibiting the secretion of PTH. It is used in secondary hyperparathyroidism and parathyroid carcinoma. * **Carisoprodol (Option C):** It is a centrally acting **skeletal muscle relaxant** used for acute musculoskeletal pain. It acts primarily through its metabolite, meprobamate, at the GABA-A receptor. * **Oxethazaine (Option D):** It is a potent **local anesthetic** used in antacid suspensions (Mucaine gel). It remains ionized in acidic gastric juice, providing symptomatic relief in gastritis and GERD. **High-Yield Clinical Pearls for NEET-PG:** * **Black Box Warning:** Teriparatide carries a risk of **Osteosarcoma** (observed in rat studies); hence, it is contraindicated in patients with Paget’s disease or prior radiation therapy. * **Duration of Use:** Treatment is generally limited to **2 years** in a lifetime. * **Abaloparatide:** A newer recombinant analog of PTH-related protein (PTHrP) used for similar indications. * **Denosumab:** A monoclonal antibody against **RANKL**, often confused with PTH analogs in exams; it is an antiresorptive agent, not an anabolic one.

Question 375: Metformin is NOT effective in lowering blood sugar levels in which of the following patients?

A. Non-diabetics (Correct Answer)
B. Obese diabetics
C. Type 2 diabetics
D. Diabetics not responding to sulfonylureas

Explanation: **Explanation:** Metformin, a biguanide, is unique among oral hypoglycemic agents because it is an **euglycemic** drug rather than a hypoglycemic drug. Its primary mechanism of action is to decrease hepatic glucose production (gluconeogenesis) and improve insulin sensitivity in peripheral tissues. **1. Why "Non-diabetics" is the correct answer:** Metformin does not stimulate insulin release from pancreatic beta cells. In non-diabetic individuals, where hepatic glucose production and peripheral insulin sensitivity are already within physiological limits, Metformin does not further lower blood glucose levels. Therefore, it **does not cause hypoglycemia** in healthy individuals, making it ineffective at lowering sugar levels below the normal baseline. **2. Analysis of Incorrect Options:** * **Obese diabetics:** Metformin is the first-line drug of choice here because it promotes modest weight loss and addresses the core issue of insulin resistance common in obesity. * **Type 2 diabetics:** This is the primary indication for Metformin. It effectively lowers HbA1c by 1–1.5% by suppressing excessive hepatic glucose output. * **Diabetics not responding to sulfonylureas:** Metformin is often added as a second-line agent or used as a substitute when sulfonylureas fail (secondary failure), as it works via a different, insulin-independent mechanism. **High-Yield NEET-PG Pearls:** * **Mechanism:** Activates **AMP-activated protein kinase (AMPK)**. * **Side Effects:** Most common are GI-related (diarrhea, abdominal pain). The most serious but rare side effect is **Lactic Acidosis**. * **Contraindication:** Renal impairment (CrCl <30 ml/min) due to the risk of lactic acid accumulation. * **Vitamin Deficiency:** Long-term use can lead to **Vitamin B12 deficiency** due to interference with its absorption in the ileum.

Question 376: Which of the following statements regarding thioamide drugs is correct?

A. They aggregate endocrine exophthalmos.
B. They are safe in children. (Correct Answer)
C. They produce irreversible hypothyroidism.
D. They do not produce relapse.

Explanation: Thioamides (Propylthiouracil and Methimazole/Carbimazole) are the mainstay of medical management for hyperthyroidism. **Why Option B is correct:** Thioamides are considered the **first-line treatment for hyperthyroidism in children and adolescents**. Unlike radioactive iodine (RAI), which carries theoretical risks of carcinogenesis or genetic damage in young developing tissues, or surgery, which carries risks of hypoparathyroidism and nerve damage, thioamides are safe for long-term use. Methimazole is generally preferred in children due to the lower risk of severe hepatotoxicity compared to Propylthiouracil (PTU). **Why the other options are incorrect:** * **Option A:** Thioamides do **not** aggravate endocrine exophthalmos. In fact, they are preferred over Radioactive Iodine (RAI) in patients with active Graves' ophthalmopathy, as RAI can acutely worsen eye disease due to the release of thyroid antigens. * **Option C:** Thioamides cause **reversible** inhibition of thyroid hormone synthesis by inhibiting thyroid peroxidase. Once the drug is discontinued, thyroid function typically returns to its baseline state. * **Option D:** Relapse is a significant drawback of thioamide therapy. Even after a full 12–18 month course, the **relapse rate for Graves' disease is approximately 50-60%**. **High-Yield NEET-PG Pearls:** * **Mechanism:** Inhibits Thyroid Peroxidase (TPO) enzyme; PTU also inhibits peripheral conversion of T4 to T3. * **Pregnancy:** PTU is preferred in the **1st trimester** (less teratogenic); Methimazole is preferred in the **2nd and 3rd trimesters** (less hepatotoxic). * **Side Effects:** The most serious side effect is **agranulocytosis** (presents as sore throat/fever); the most common is a maculopapular rash.

Question 377: Newer insulins are generally considered to be in which pH state?

A. Acidic
B. Alkaline
C. Neutral (Correct Answer)
D. Monomers

Explanation: **Explanation:** The correct answer is **Neutral (C)**. Historically, older insulin preparations (like bovine or porcine insulin) were formulated at an **acidic pH (pH 3.0–3.5)** to ensure solubility and stability. However, acidic injections often caused local pain, tissue irritation, and lipodystrophy at the injection site. Modern "newer" insulins—including **Human Regular Insulin** and rapid-acting analogs like **Lispro, Aspart, and Glulisine**—are formulated at a **neutral pH (approximately 7.0–7.4)**. This shift was made possible by recombinant DNA technology, which allows for highly purified preparations that remain stable and soluble at physiological pH. Neutral pH formulations are better tolerated, cause less injection-site pain, and are more compatible with physiological fluids. **Analysis of Incorrect Options:** * **A. Acidic:** While older insulins were acidic, only one modern analog, **Insulin Glargine**, remains acidic (pH 4.0). This acidity is necessary to keep Glargine soluble in the vial; once injected into the neutral pH of subcutaneous tissue, it precipitates to form a slow-release depot. * **B. Alkaline:** Insulin is not formulated at an alkaline pH as it would be unstable and cause significant tissue damage. * **D. Monomers:** This describes a **structural state**, not a pH state. While rapid-acting analogs exist as monomers (or dissociate quickly into them), the question specifically asks for the pH state. **NEET-PG High-Yield Pearls:** * **The Glargine Exception:** Insulin Glargine is the only modern insulin that is **acidic**. Because of this, it **cannot be mixed** in the same syringe with neutral insulins (like Regular or NPH), as it will precipitate prematurely. * **Soluble Insulin:** Regular insulin is also known as "Neutral Insulin" or "Soluble Insulin." * **Stability:** Neutral pH preparations have a longer shelf-life and lower immunogenicity compared to older acidic formulations.

Question 378: Which of the following statements is true?

A. Clomiphene acts as an antiestrogen on both the pituitary and hypothalamus.
B. Danazol increases both FSH and LH.
C. Methimazole inhibits thyroxine release from the thyroid.
D. Cyproterone is a potent antiandrogen. (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Cyproterone is a potent antiandrogen.** Cyproterone acetate is a competitive antagonist at the androgen receptor. It also possesses progestational activity, which suppresses LH secretion via negative feedback, further reducing testosterone levels. It is clinically used to treat hirsutism in females, precocious puberty in boys, and as palliative therapy for prostatic carcinoma. **Analysis of Incorrect Options:** * **A. Clomiphene:** While clomiphene acts as an **antiestrogen** in the hypothalamus and pituitary (blocking negative feedback to increase GnRH, FSH, and LH), it acts as a **weak agonist (estrogenic)** in the uterus and vagina. It is classified as a Selective Estrogen Receptor Modulator (SERM). * **B. Danazol:** Danazol is an ethisterone derivative that **decreases** FSH and LH secretion by inhibiting the mid-cycle surge. It creates a "pseudomenopause" state and is used in endometriosis and hereditary angioedema. * **C. Methimazole:** Methimazole (and PTU) inhibits the enzyme **thyroid peroxidase**, thereby blocking the synthesis (organification and coupling) of thyroid hormones. It does **not** inhibit the release of preformed hormones; that is the mechanism of action of **Iodides** (Lugol’s iodine). **High-Yield NEET-PG Pearls:** * **Cyproterone vs. Flutamide:** Flutamide is a pure antiandrogen (no progestational activity) often used in prostatic cancer to prevent the "testosterone flare" caused by GnRH agonists. * **Clomiphene:** The drug of choice for infertility due to anovulation (PCOS). A common side effect is multiple pregnancies. * **Thioamides:** Methimazole is preferred over PTU due to a longer half-life and lower hepatotoxicity, except in the **first trimester of pregnancy** and thyroid storm, where PTU is preferred.

Question 379: Which of the following statements about biguanides is NOT true?

A. Do not stimulate insulin release
B. Decrease hepatic glucose production
C. Renal dysfunction is not a contraindication for their use (Correct Answer)
D. Can be combined with sulfonylureas

Explanation: **Explanation:** Biguanides, primarily **Metformin**, are the first-line pharmacological agents for Type 2 Diabetes Mellitus. Understanding their safety profile and mechanism is crucial for NEET-PG. **Why Option C is the correct (False) statement:** Metformin is primarily excreted unchanged by the kidneys. In patients with renal impairment, the drug accumulates, significantly increasing the risk of **Lactic Acidosis**—a rare but potentially fatal metabolic complication. Therefore, renal dysfunction is a **strict contraindication**. Current guidelines suggest Metformin should not be initiated if the eGFR is <45 ml/min and must be discontinued if the eGFR falls below 30 ml/min. **Analysis of other options:** * **Option A (True):** Unlike sulfonylureas, biguanides are **euglycemic** agents. They do not stimulate pancreatic beta cells to release insulin; hence, they do not cause hypoglycemia when used as monotherapy. * **Option B (True):** The primary mechanism of Metformin is the activation of **AMP-activated protein kinase (AMPK)**, which leads to decreased hepatic gluconeogenesis (glucose production). * **Option D (True):** Metformin is frequently combined with sulfonylureas (like Glimepiride) to achieve synergistic glycemic control, as they have different mechanisms of action. **High-Yield Clinical Pearls for NEET-PG:** 1. **Mechanism:** Inhibits mitochondrial complex I and activates AMPK. 2. **Weight Neutrality:** Metformin is often associated with modest weight loss, making it ideal for obese diabetics. 3. **Side Effects:** Gastrointestinal upset (most common) and **Vitamin B12 deficiency** (long-term use). 4. **Pleiotropic Benefits:** It improves lipid profiles and is used off-label in Polycystic Ovary Syndrome (PCOS) to improve insulin sensitivity.

Question 380: Which of the following is NOT an antithyroid drug?

A. Propylthiouracil
B. Methimazole
C. Carbimazole
D. Carbamazepine (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Carbamazepine**. **1. Why Carbamazepine is the correct answer:** Carbamazepine is an **anti-epileptic drug (AED)** and a sodium channel blocker used primarily for generalized tonic-clonic seizures, focal seizures, and trigeminal neuralgia. It has no therapeutic role in inhibiting thyroid hormone synthesis or release. In fact, it is a potent **cytochrome P450 enzyme inducer**, which can actually increase the metabolism of thyroid hormones, potentially necessitating dose adjustments in hypothyroid patients on levothyroxine. **2. Why the other options are incorrect:** * **Propylthiouracil (PTU):** A thioamide antithyroid drug. It inhibits the enzyme **thyroid peroxidase (TPO)**, blocking iodine organification and coupling. Unique to PTU is its ability to inhibit the **peripheral conversion of T4 to T3**, making it preferred in thyroid storm. * **Methimazole:** The most commonly used thioamide. It is more potent and has a longer half-life than PTU. It also works by inhibiting TPO. * **Carbimazole:** A **prodrug** that is rapidly converted to methimazole in the body. It shares the same mechanism of action and clinical indications. **3. High-Yield Clinical Pearls for NEET-PG:** * **Teratogenicity:** Methimazole/Carbimazole are associated with **Aplasia Cutis** (scalp defects) and choanal atresia. Therefore, **PTU is preferred in the 1st trimester** of pregnancy. * **Hepatotoxicity:** PTU carries a black box warning for severe liver failure; Methimazole is generally preferred in the 2nd and 3rd trimesters. * **Adverse Effect:** The most serious side effect of thioamides is **agranulocytosis** (presents as sore throat/fever). * **Wolff-Chaikoff Effect:** High doses of iodine (Lugol's iodine) acutely inhibit thyroid hormone release.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

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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