Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 471: In the treatment of hypothyroidism, why is thyroxine generally preferred over liothyronine?

A. Thyroxine has a faster onset of action.
B. Thyroxine exhibits higher affinity for thyroid hormone receptors.
C. Thyroxine possesses a longer half-life. (Correct Answer)
D. Thyroxine can be synthesized more readily using recombinant DNA technology.

Explanation: The preference for **Thyroxine (T4)** over **Liothyronine (T3)** in the management of hypothyroidism is primarily based on its pharmacokinetic profile and physiological behavior. Synthetic levothyroxine is the preparation of choice for thyroid replacement and suppression therapy [1]. Monotherapy with levothyroxine most closely mimics normal physiology and is generally preferred [2]. **1. Why the Correct Answer is Right:** Thyroxine (T4) has a significantly **longer half-life (approx. 7 days)** compared to Liothyronine (T3), which has a half-life of about 1 day [2]. This long half-life allows for **once-daily dosing**, ensuring stable serum levels and better patient compliance [2]. Furthermore, T4 acts as a pro-hormone; the body deiodinates it into T3 (the active form) in peripheral tissues as needed [1]. This provides a steady, physiological supply of T3, avoiding the "peaks and troughs" associated with direct T3 administration [2]. **2. Why Incorrect Options are Wrong:** * **Option A:** T3 is the active hormone and has a **faster onset** of action than T4. This makes T3 useful in emergencies like myxedema coma, but not for routine maintenance. * **Option B:** T3 actually has a **higher affinity** (about 10 times greater) for nuclear thyroid receptors than T4. * **Option D:** Thyroid hormones are small iodinated amino acids, not proteins; they are synthesized via chemical synthesis, not recombinant DNA technology. **Clinical Pearls for NEET-PG:** * **Drug of Choice:** Levothyroxine (T4) is the DOC for hypothyroidism. * **Monitoring:** Serum **TSH** is the most sensitive marker for monitoring T4 therapy (target: 0.5–2.5 mIU/L). * **Administration:** Should be taken on an **empty stomach** (30–60 mins before breakfast) as food, calcium, and iron supplements decrease its absorption. * **Myxedema Coma:** Intravenous Liothyronine (T3) or Levothyroxine (T4) can be used, but T3 is often preferred for its rapid effect.

Question 472: All of the following are used in the treatment of hypercalcemia, except:

A. Phosphate
B. Mithramycin
C. Vitamin D in high dose (Correct Answer)
D. Any of the above

Explanation: **Explanation:** The management of hypercalcemia focuses on reducing serum calcium levels by inhibiting bone resorption, increasing renal excretion, or decreasing intestinal absorption. **Why Vitamin D is the Correct Answer:** Vitamin D (in high doses) is **contraindicated** in hypercalcemia because its primary physiological role is to **increase** serum calcium levels. It achieves this by enhancing intestinal calcium absorption and stimulating osteoclast activity (bone resorption). Administering high-dose Vitamin D would exacerbate hypercalcemia, potentially leading to a hypercalcemic crisis. In fact, Vitamin D toxicity is a known cause of hypercalcemia. **Analysis of Other Options:** * **Phosphate (Option A):** Intravenous or oral phosphate can be used to treat hypercalcemia. It works by promoting the deposition of calcium into the bone and soft tissues (forming calcium phosphate), thereby lowering serum levels. However, it is used cautiously due to the risk of ectopic calcification. * **Mithramycin (Plicamycin) (Option B):** This is a cytotoxic antibiotic that, in lower doses, acts as a potent inhibitor of osteoclastic bone resorption. It was traditionally used for hypercalcemia of malignancy, though it has largely been replaced by bisphosphonates due to toxicity. **NEET-PG High-Yield Pearls:** * **First-line treatment:** Vigorous rehydration with **Normal Saline (0.9% NaCl)** is the most crucial initial step. * **Loop Diuretics:** Furosemide is used *after* rehydration to promote calciuresis (forced diuresis). * **Bisphosphonates (e.g., Zoledronate, Pamidronate):** These are the drugs of choice for hypercalcemia of malignancy. * **Calcitonin:** Used for rapid, short-term reduction of calcium (works within hours but exhibits tachyphylaxis). * **Glucocorticoids:** Effective specifically for hypercalcemia caused by sarcoidosis, lymphomas, or Vitamin D intoxication.

Question 473: Which is not a side effect of Growth Hormone (GH) administration?

A. Gynecomastia
B. Hypoglycemia (Correct Answer)
C. Slipped capital femoral epiphysis
D. Pseudotumor cerebri

Explanation: **Explanation:** Growth Hormone (GH) administration is associated with several metabolic and structural side effects, but it does **not** cause hypoglycemia. **1. Why Hypoglycemia is the correct answer:** Growth Hormone is a **diabetogenic hormone**. It antagonizes the action of insulin, decreases peripheral glucose utilization, and increases hepatic gluconeogenesis. Therefore, GH administration leads to **hyperglycemia** and insulin resistance, not hypoglycemia. In patients with pre-existing diabetes, GH therapy often necessitates an increase in insulin dosage. **2. Analysis of incorrect options:** * **Gynecomastia:** GH has structural similarities to Prolactin and can stimulate mammary tissue, leading to gynecomastia in some males. * **Slipped Capital Femoral Epiphysis (SCFE):** Rapid longitudinal bone growth induced by GH can place mechanical stress on the growth plates, particularly in the hip, making SCFE a known orthopedic complication in children. * **Pseudotumor Cerebri (Idiopathic Intracranial Hypertension):** GH can cause fluid retention and altered CSF dynamics, leading to increased intracranial pressure, headache, and papilledema. **Clinical Pearls for NEET-PG:** * **Metabolic effects:** GH increases lipolysis (increasing free fatty acids) and promotes a positive nitrogen balance (anabolic). * **Monitoring:** Children on GH therapy should be monitored for limping (SCFE) and severe headaches (Pseudotumor cerebri). * **Laron Syndrome:** A condition of GH resistance due to receptor mutations; treated with **Mecasermin** (recombinant IGF-1). * **Somatostatin Analogs:** Octreotide and Lanreotide are used to treat Acromegaly by inhibiting GH secretion.

Question 474: Gestrinone has the following actions except?

A. Androgenic
B. Anti-oestrogenic
C. Anti-androgenic (Correct Answer)
D. Anti-progestogenic

Explanation: **Explanation:** Gestrinone is a synthetic steroid derivative of 19-nortestosterone primarily used in the treatment of endometriosis. To understand its mechanism, it is essential to recognize its **mixed agonist-antagonist profile** on various steroid receptors. **Why "Anti-androgenic" is the correct answer:** Gestrinone possesses significant **androgenic** activity rather than anti-androgenic activity. It binds to androgen receptors and exerts agonist effects, which contributes to its side effect profile (e.g., weight gain, acne, and hirsutism). Therefore, stating it is "anti-androgenic" is pharmacologically incorrect. **Analysis of other options:** * **Androgenic (A):** As a 19-nortestosterone derivative, it has inherent weak androgenic properties. * **Anti-oestrogenic (B):** It acts centrally to suppress the mid-cycle surge of LH and FSH, leading to decreased ovarian estrogen production. It also has direct antagonistic effects at the endometrial level. * **Anti-progestogenic (D):** Gestrinone acts as a selective progesterone receptor modulator (SPRM) with predominant **antagonist** activity on the endometrium, leading to atrophy of ectopic endometrial tissue. **Clinical Pearls for NEET-PG:** * **Primary Indication:** Second-line treatment for **Endometriosis** (similar efficacy to Danazol but with a longer half-life, allowing twice-weekly dosing). * **Mechanism Summary:** It creates a "high-androgen, low-estrogen" environment that induces atrophy of the endometrium. * **Contraindications:** Pregnancy (due to virilization of a female fetus) and severe hepatic/renal impairment. * **Key Side Effects:** Acne, oily skin, hirsutism, and voice changes (due to its androgenic nature).

Question 475: All of the following antidiabetic drugs act by enhancing insulin sensitivity except?

A. Exenatide
B. Sitagliptin
C. Rosiglitazone (Correct Answer)
D. Repaglinide

Explanation: **Explanation:** The question asks for drugs that **do not** act by enhancing insulin sensitivity. However, there is a discrepancy in the provided key: **Rosiglitazone is an insulin sensitizer**, while **Exenatide, Sitagliptin, and Repaglinide are not.** In pharmacological terms, antidiabetic drugs are classified by their primary mechanism: 1. **Insulin Sensitizers:** These drugs improve the body's response to insulin without increasing insulin secretion. [3] * **Biguanides (Metformin):** Activates AMPK. * **Thiazolidinediones (Rosiglitazone, Pioglitazone):** Activate **PPAR-̳** receptors in adipose tissue and muscle. [1] 2. **Insulin Secretagogues:** These drugs stimulate the pancreas to release more insulin. [5] * **Sulfonylureas & Meglitinides (Repaglinide):** Close ATP-sensitive K+ channels. [1], [4] 3. **Incretin-based Therapies:** * **GLP-1 Agonists (Exenatide):** Mimic incretin hormones to increase glucose-dependent insulin secretion. [2] * **DPP-4 Inhibitors (Sitagliptin):** Prevent the breakdown of endogenous GLP-1. **Analysis of Options:** * **Rosiglitazone (Option C):** This is a classic **insulin sensitizer**. If the question asks for a drug that *does* enhance sensitivity, this is the correct answer. If the question asks for an "except," this option is technically incorrect. * **Repaglinide (Option D):** A meglitinide that acts as a secretagogue. [1], [4] * **Exenatide & Sitagliptin (Options A & B):** Act via the incretin pathway to increase insulin secretion. [2], [5] **NEET-PG High-Yield Pearls:** * **PPAR-̳** is the molecular target for "Glitazones." * **Metformin** is the first-line agent for Type 2 DM and is weight-neutral/weight-reducing. * **SGLT-2 Inhibitors (-gliflozins)** are the only class that acts independently of insulin by causing glucosuria. * **Side effect alert:** Pioglitazone is associated with bladder cancer and weight gain, while Metformin can cause Vitamin B12 deficiency.

Question 476: All of the following are effects of estrogen, EXCEPT:

A. Beneficial effect on cognition
B. Reduced osteoclastic activity
C. Increased osteoblastic activity
D. Increased protein C and S levels (Correct Answer)

Explanation: **Explanation:** The correct answer is **D (Increased protein C and S levels)** because estrogen actually **decreases** the levels of Protein C and Protein S (natural anticoagulants) and increases the levels of clotting factors (II, VII, IX, and X). This shift creates a **pro-thrombotic state**, increasing the risk of deep vein thrombosis (DVT) and pulmonary embolism. **Analysis of Options:** * **A. Beneficial effect on cognition:** Estrogen has neuroprotective properties. It enhances synaptic plasticity and cerebral blood flow, which is why postmenopausal estrogen deficiency is often linked to "brain fog" or cognitive decline. * **B & C. Effects on Bone (Osteoclasts/Osteoblastic activity):** Estrogen is vital for bone health. It **reduces osteoclastic activity** (by inducing apoptosis of osteoclasts and inhibiting RANKL) and **increases osteoblastic activity** (by stimulating TGF-β). This dual action prevents bone resorption and maintains bone mineral density. **NEET-PG High-Yield Pearls:** * **Lipid Profile:** Estrogen increases HDL ("good" cholesterol) and decreases LDL, but it also **increases Triglycerides**. * **Biliary System:** It increases cholesterol secretion in bile, leading to a higher risk of **gallstones** (cholelithiasis). * **Cancer Risk:** Unopposed estrogen increases the risk of **endometrial carcinoma**; hence, it is always combined with progestins in women with an intact uterus. * **Metabolism:** Estrogen increases the synthesis of transport proteins in the liver, such as Sex Hormone Binding Globulin (SHBG) and Thyroid Binding Globulin (TBG).

Question 477: Which of the following is NOT a true statement regarding oral hypoglycemic agents?

A. They are effective only after total pancreatectomy. (Correct Answer)
B. Metformin is associated with a risk of lactic acidosis.
C. Some agents stimulate the release of insulin from pancreatic beta-cells.
D. They are useful in obese patients with maturity-onset diabetes.

Explanation: ### Explanation **1. Why Option A is the Correct Answer (The False Statement):** Oral hypoglycemic agents (OHAs), specifically secretagogues like Sulfonylureas and Meglitinides, require **functional pancreatic beta-cells** to exert their effect [1]. A total pancreatectomy results in the absolute loss of all beta-cells, leading to surgical diabetes (similar to Type 1 DM). In the absence of endogenous insulin production, OHAs are completely ineffective. Patients post-pancreatectomy require exogenous insulin therapy for survival. **2. Analysis of Incorrect Options (True Statements):** * **Option B:** Metformin (a Biguanide) inhibits mitochondrial respiration, which can lead to an accumulation of lactate. While rare, **lactic acidosis** is a serious potential side effect, especially in patients with renal impairment or hepatic failure. * **Option C:** Sulfonylureas (e.g., Glipizide) and Meglitinides (e.g., Repaglinide) act by closing ATP-sensitive potassium channels on beta-cells, causing depolarization and subsequent **insulin release** [1], [2]. * **Option D:** **Metformin** is the first-line drug for obese patients with Type 2 Diabetes (maturity-onset) because it promotes modest weight loss and improves insulin sensitivity without causing hypoglycemia [3]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Metformin is the first-line agent for Type 2 DM unless contraindicated (CrCl <30 mL/min) [3]. * **Weight Neutral/Loss:** Metformin and GLP-1 agonists (e.g., Liraglutide) help with weight loss; SGLT-2 inhibitors (e.g., Dapagliflozin) also promote weight loss via glucosuria [3]. * **Weight Gain:** Sulfonylureas and Thiazolidinediones (Pioglitazone) are associated with weight gain. * **Disulfiram-like reaction:** Classically associated with first-generation sulfonylureas like **Chlorpropamide**.

Question 478: Lactic acidosis is a potential side effect of which of the following medications?

A. Chlorothiazide
B. Metformin (Correct Answer)
C. Cyclosporine
D. Pentamidine

Explanation: **Explanation:** **Correct Answer: B. Metformin** Metformin, a Biguanide, is the first-line agent for Type 2 Diabetes Mellitus [1]. Its primary mechanism involves the activation of **AMP-activated protein kinase (AMPK)**, which leads to decreased hepatic gluconeogenesis. A critical metabolic consequence of metformin is the inhibition of **pyruvate carboxylase** and the mitochondrial respiratory chain (Complex I). This inhibition prevents the conversion of lactate back into glucose (gluconeogenesis), leading to an accumulation of lactate in the blood. While rare, **Metformin-Associated Lactic Acidosis (MALA)** is a life-threatening complication, especially in patients with renal impairment (eGFR <30 ml/min), as the drug is excreted unchanged by the kidneys [1]. **Incorrect Options:** * **A. Chlorothiazide:** A thiazide diuretic primarily associated with metabolic alkalosis (due to hypokalemia and H+ loss) and hyperglycemia, but not lactic acidosis. * **C. Cyclosporine:** An immunosuppressant (calcineurin inhibitor) known for nephrotoxicity, hypertension, and hyperkalemia, but it does not typically cause lactic acidosis. * **D. Pentamidine:** Used for *Pneumocystis jirovecii*, it is notorious for causing pancreatic toxicity (hypoglycemia followed by hyperglycemia) and nephrotoxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Metformin side effects:** **L**actic acidosis, **A**norexia, **M**etallic taste, **B**12 deficiency (megaloblastic anemia). * **Contraindication:** Metformin must be temporarily discontinued before **IV contrast** studies to prevent acute kidney injury, which could precipitate lactic acidosis. * **Weight Neutrality:** Unlike sulfonylureas or insulin, Metformin does not cause weight gain and is often associated with modest weight loss [2].

Question 479: Bisphosphonates act by which of the following mechanisms?

A. Increasing osteoid formation
B. Increasing the mineralization of osteoid
C. Decreasing osteoclast-mediated resorption of bone (Correct Answer)
D. Decreasing parathyroid hormone secretion

Explanation: **Explanation:** **Mechanism of Action (Why C is correct):** Bisphosphonates are synthetic analogs of pyrophosphate that have a high affinity for hydroxyapatite crystals in the bone. They primarily act by **inhibiting osteoclast-mediated bone resorption**. * **Simple Bisphosphonates (e.g., Etidronate):** Are metabolized into non-functional ATP analogs that induce osteoclast apoptosis. * **Nitrogen-containing Bisphosphonates (e.g., Alendronate, Zoledronate):** Inhibit the enzyme **farnesyl pyrophosphate (FPP) synthase** in the mevalonate pathway. This prevents the prenylation of GTP-binding proteins (like Rho and Ras) necessary for osteoclast survival and their "ruffled border" formation, leading to reduced bone resorption. **Analysis of Incorrect Options:** * **Options A & B:** Bisphosphonates do not stimulate osteoblasts or increase osteoid formation/mineralization. In fact, high doses of older bisphosphonates (Etidronate) can actually *impair* mineralization. Drugs that increase bone formation (anabolic agents) include Teriparatide. * **Option D:** Bisphosphonates do not directly affect the parathyroid gland. However, by decreasing bone resorption, they may cause a transient compensatory *increase* in PTH due to a slight drop in serum calcium. **High-Yield NEET-PG Pearls:** * **Drug of Choice:** Bisphosphonates are the first-line treatment for **Postmenopausal Osteoporosis** and **Paget’s Disease**. * **Administration:** Oral bisphosphonates (Alendronate) must be taken on an empty stomach with a full glass of water, and the patient must remain upright for 30 minutes to prevent **erosive esophagitis**. * **Adverse Effects:** Osteonecrosis of the Jaw (ONJ) and atypical subtrochanteric fractures (with long-term use). * **Potency:** Zoledronate is the most potent bisphosphonate and is administered intravenously once yearly.

Question 480: Which drug decreases the efficacy of testosterone?

A. Isoniazid
B. Ketoconazole (Correct Answer)
C. Rifampicin
D. None

Explanation: **Explanation** The correct answer is **Ketoconazole**. **Mechanism of Action (Why it is correct):** Ketoconazole is a broad-spectrum imidazole antifungal that acts as a potent inhibitor of steroid synthesis. It inhibits the enzyme **17,20-lyase** (and to a lesser extent, CYP11A1/side-chain cleavage enzyme), which are essential steps in the conversion of cholesterol to androgens. By blocking these enzymes in both the testes and the adrenal glands, it significantly reduces testosterone production. Additionally, at high doses, it can displace testosterone from sex hormone-binding globulin (SHBG), further altering its efficacy. **Analysis of Incorrect Options:** * **Isoniazid (A):** While Isoniazid is a CYP450 inhibitor, it does not have a clinically significant effect on the steroidogenic pathways or the efficacy of testosterone. Its primary side effects are peripheral neuropathy and hepatotoxicity. * **Rifampicin (C):** Rifampicin is a potent **enzyme inducer**. While it can increase the metabolism of many steroid hormones (like oral contraceptives), it does not directly decrease the efficacy of testosterone in the same targeted, inhibitory manner as Ketoconazole. In fact, it often leads to a compensatory rise in LH and testosterone levels. **Clinical Pearls for NEET-PG:** * **Anti-androgenic side effects:** Due to testosterone inhibition, Ketoconazole can cause **gynecomastia**, decreased libido, and erectile dysfunction in men. * **Clinical Use:** Because of its ability to inhibit steroidogenesis, high-dose Ketoconazole is sometimes used off-label to treat **Cushing’s syndrome** and advanced **prostate cancer**. * **Other Drugs causing Gynecomastia (Mnemonic: DISCO):** **D**igoxin, **I**soniazid (rarely), **S**pironolactone, **C**imetidine, **O**estrogens/Ketoconazole.

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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