Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 711: Which Selective Estrogen Receptor Modulator (SERM) is used in the treatment of Dysfunctional Uterine Bleeding (DUB)?

A. Clomiphene
B. Raloxifene
C. Ormiloxifene (Correct Answer)
D. Tamoxifen

Explanation: ***Correct: Ormiloxifene*** - Ormiloxifene is a **selective estrogen receptor modulator (SERM)** specifically approved and used for the management of **dysfunctional uterine bleeding (DUB)**. - It works by acting as an **estrogen antagonist on the endometrium**, which influences the endometrial lining to regulate bleeding patterns and **reduce menstrual blood loss**. - Marketed as **Sevista/Saheli** in India. *Incorrect: Clomiphene* - Clomiphene is primarily used as an **ovulation inducer** in women with infertility due to anovulation [1]. - It acts by blocking estrogen receptors in the hypothalamus, thereby increasing the secretion of gonadotropins [1]. - Not indicated for treatment of DUB. *Incorrect: Raloxifene* - Raloxifene is indicated for the prevention and treatment of **postmenopausal osteoporosis** and the reduction of invasive breast cancer risk in certain high-risk women [1][2]. - It has estrogen-agonist effects on bone and antagonist effects on breast and uterine tissue [1][2]. - Not used for management of DUB. *Incorrect: Tamoxifen* - Tamoxifen is widely used in the treatment of **estrogen receptor-positive breast cancer** in both pre- and postmenopausal women [1][2]. - It acts as an estrogen antagonist in breast tissue but has **estrogen-agonist effects on the endometrium**, which can cause endometrial hyperplasia or cancer [1][2]. - Not indicated for DUB treatment.

Question 712: What is a therapeutic indication for the use of liothyronine?

A. Resistant depression (Correct Answer)
B. Social phobia
C. Cataplexy
D. Alzheimer's disease

Explanation: ***Resistant depression*** - Liothyronine (T3) can be used as an **adjunctive therapy** for patients with major depressive disorder who have not responded adequately to antidepressant monotherapy. - While the exact mechanism is not fully understood, it's thought to improve antidepressant response by modulating **neurotransmitter systems** and receptor sensitivity in the brain. *Social phobia* - **Social phobia**, or social anxiety disorder, is primarily treated with psychotherapy (e.g., CBT) and medications like **SSRIs** or **SNRIs**. - Liothyronine is **not a primary or adjunctive treatment** for social phobia. *Alzheimer's disease* - **Alzheimer's disease** is a neurodegenerative disorder treated with cholinesterase inhibitors (e.g., donepezil) and NMDA receptor antagonists (e.g., memantine). - There is currently **no established role for liothyronine** in the treatment of Alzheimer's disease. *Cataplexy* - **Cataplexy**, a symptom of narcolepsy, is characterized by sudden muscle weakness triggered by strong emotions. - It is typically managed with medications like **sodium oxybate** or certain antidepressants (e.g., venlafaxine), not liothyronine.

Question 713: Which of the following are medical management options for hyperparathyroidism?

A. Bisphosphonates
B. Calcitonin
C. Plicamycin
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Bisphosphonates**, **calcitonin**, and **plicamycin** (mithramycin) are all therapeutic options used in the medical management of hyperparathyroidism, particularly for reducing hypercalcemia. - These agents work through different mechanisms to lower serum calcium levels, which is a primary goal in managing significant hyperparathyroidism. *Bisphosphonates* - **Bisphosphonates** inhibit osteoclast activity, thereby reducing **bone resorption** and subsequently lowering serum calcium levels. - They are particularly useful for long-term management of hypercalcemia associated with hyperparathyroidism. *Calcitonin* - **Calcitonin** directly inhibits osteoclast activity and increases renal calcium excretion, leading to a relatively rapid, but often short-lived, decrease in serum calcium. - It is often used for the **acute management** of severe hypercalcemia due to its quick onset of action. *Plicamycin* - **Plicamycin** (also known as mithramycin) is an antineoplastic antibiotic that inhibits RNA synthesis and has been shown to reduce serum calcium by inhibiting osteoclast-mediated bone resorption. - Due to its potential for significant side effects, including **renal**, **hepatic**, and **hematologic toxicity**, its use is generally reserved for severe, refractory hypercalcemia.

Question 714: Which of the following drugs is known to reduce the risk of both macrovascular and microvascular complications of diabetes mellitus?

A. Metformin (Correct Answer)
B. Acarbose
C. Repaglinide
D. Sitagliptin

Explanation: ***Metformin*** - **Metformin** is the first-line drug for type 2 diabetes with established evidence from the **UKPDS (UK Prospective Diabetes Study)** demonstrating reduction in both **macrovascular** (cardiovascular events, myocardial infarction) and **microvascular** (retinopathy, nephropathy, neuropathy) complications [1] - Particularly effective in **overweight and obese patients**, reducing diabetes-related mortality and all-cause mortality [1] - Mechanisms include decreasing **hepatic glucose production** [3], reducing intestinal glucose absorption, and improving **insulin sensitivity** [1] - Remains the **gold standard** first-line therapy per ADA/EASD guidelines *Acarbose* - Alpha-glucosidase inhibitor that delays carbohydrate absorption in the gut, reducing postprandial glucose excursions [2] - Provides glycemic control but **lacks robust evidence** for significant reduction in both macrovascular and microvascular complications - Primary benefit is in postprandial glucose management, not long-term complication prevention *Repaglinide* - Meglitinide analog that stimulates rapid, short-acting insulin release from pancreatic beta cells [1] - Effective for **postprandial hyperglycemia control** but lacks definitive large-scale trial evidence showing reduction in both macrovascular and microvascular outcomes - No cardiovascular outcome trials demonstrating complication reduction comparable to metformin *Sitagliptin* - DPP-4 inhibitor that enhances incretin hormone activity to improve glycemic control - **TECOS trial** showed cardiovascular safety (non-inferiority) but **not superiority** in reducing macrovascular or microvascular complications - Benefits include weight neutrality and low hypoglycemia risk, but less direct evidence for widespread complication reduction compared to metformin

Question 715: Mechanism of action of Teriparatide?

A. Stimulates lactation and affects reproductive hormones
B. Regulates glucose metabolism and insulin sensitivity
C. Stimulates osteoblast activity and increases bone formation (Correct Answer)
D. Inhibits osteoclast activity and decreases bone resorption

Explanation: ***Stimulates osteoblast activity and increases bone formation*** - **Teriparatide** is a recombinant form of **parathyroid hormone (PTH)**. When administered intermittently, it primarily **stimulates osteoblasts** to form new bone, leading to increased bone density and strength. - This anabolic effect makes it effective in treating **osteoporosis** by promoting bone formation rather than just inhibiting bone breakdown. *Regulates glucose metabolism and insulin sensitivity* - This mechanism describes the action of drugs such as **metformin** or **GLP-1 agonists**, which are used in the treatment of **diabetes mellitus**. - **Teriparatide** is not involved in glucose regulation or insulin sensitivity. *Stimulates lactation and affects reproductive hormones* - This mechanism is characteristic of hormones like **prolactin** or drugs that modulate **gonadotropin-releasing hormone (GnRH)**, which are involved in reproductive health. - **Teriparatide's** primary role is bone metabolism, not lactation or reproductive hormone modulation. *Inhibits osteoclast activity and decreases bone resorption* - This mechanism describes the action of **bisphosphonates** or **calcitonin**, which are anti-resorptive agents used to treat osteoporosis by reducing the breakdown of bone. - **Teriparatide**, in contrast, has an overall **anabolic effect** on bone by stimulating bone formation, even though continuous PTH elevation can cause osteoclast activity.

Question 716: Which of the following drug classes is INCORRECTLY matched with its mechanism of action?

A. Biguanides - AMPK activation (Correct Answer)
B. Alpha-glucosidase inhibitors - Delay carbohydrate absorption
C. Sulfonylureas - Block ATP-sensitive K+ channels
D. DPP-4 inhibitors - Inhibit incretin degradation

Explanation: ***Biguanides - AMPK activation*** - This statement describes an **INCORRECT** mechanism. - While metformin does have effects on cellular metabolism, its primary mechanism is **inhibition of mitochondrial complex I**, leading to decreased hepatic gluconeogenesis. - AMPK activation is a **downstream effect**, not the primary mechanism of action. - This is the incorrectly matched pair. *Alpha-glucosidase inhibitors - Delay carbohydrate absorption* - This statement describes the **correct** mechanism of action for alpha-glucosidase inhibitors. - They work by inhibiting enzymes (alpha-glucosidases) in the small intestine that break down complex carbohydrates into absorbable monosaccharides, thus **delaying glucose absorption**. *Sulfonylureas - Block ATP-sensitive K+ channels* - This statement describes the **correct** mechanism of action for sulfonylureas. - Sulfonylureas bind to and **close ATP-sensitive potassium channels** on pancreatic beta cells, leading to depolarization and increased insulin release. *DPP-4 inhibitors - Inhibit incretin degradation* - This statement describes the **correct** mechanism of action for DPP-4 inhibitors. - They work by inhibiting the enzyme **dipeptidyl peptidase-4 (DPP-4)**, which is responsible for the rapid degradation of **incretin hormones** like GLP-1 and GIP.

Question 717: What is the mechanism of action of sulfonylureas?

A. K ATP channel blocker (Correct Answer)
B. Sodium channel blocker
C. Calcium channel blocker
D. Chloride channel blocker

Explanation: ***K ATP channel blocker*** - Sulfonylureas bind to the **sulfonylurea receptor 1 (SUR1)** subunit of the **ATP-dependent potassium (KATP) channel** on pancreatic beta cells. - This binding leads to the closure of the KATP channels, causing **depolarization of the beta cell membrane** and subsequent **insulin release**. *Sodium channel blocker* - **Sodium channel blockers** are primarily used in conditions like **cardiac arrhythmias** and **epilepsy**, by stabilizing neuron membranes or altering cardiac action potentials. - They do not directly influence **insulin secretion** from pancreatic beta cells. *Calcium channel blocker* - **Calcium channel blockers** primarily inhibit the influx of calcium ions into cells, affecting **vascular smooth muscle** and **cardiac muscle**, which can influence blood pressure and heart rate. - While calcium influx is crucial for insulin release, sulfonylureas do not directly target these channels. *Chloride channel blocker* - **Chloride channel blockers** are not a primary mechanism of action for antidiabetic medications like sulfonylureas. - Their physiological roles are diverse, including involvement in **epithelial transport** and **cellular excitability**.

Question 718: Which drug is used for the medical management of acromegaly due to small pituitary tumors?

A. Vigabatrin
B. Pegvisomant
C. Octreotide (Correct Answer)
D. Cabergoline

Explanation: ***Octreotide*** - **Octreotide** is a **somatostatin analog** and the **first-line medical therapy** for acromegaly. - It effectively suppresses **growth hormone (GH)** and **IGF-1** secretion by binding to somatostatin receptors (especially SSTR2 and SSTR5) on pituitary adenomas. - Normalizes IGF-1 levels in **50-70%** of patients and can reduce tumor size. - Used for small or large tumors when surgery is not feasible, has failed, or as primary medical management. *Cabergoline* - **Cabergoline** is a **dopamine agonist** with limited efficacy in acromegaly. - Controls GH/IGF-1 in only **10-20%** of patients, primarily those with **co-secretion of prolactin** (mixed GH-PRL adenomas). - May be used as **adjunctive therapy** with somatostatin analogs but is not first-line treatment. *Pegvisomant* - **Pegvisomant** is a **GH receptor antagonist** that blocks GH action at the tissue level. - Highly effective at normalizing **IGF-1** levels (**>90%** of patients). - Used as **second-line therapy** when somatostatin analogs fail or are insufficient. - Does not reduce tumor size or GH secretion directly. *Vigabatrin* - **Vigabatrin** is an **antiepileptic drug** that inhibits GABA transaminase. - Has no role in the treatment of acromegaly or pituitary tumors.

Question 719: What is the mechanism of action of Pegvisomant?

A. Somatostatin antagonist
B. Somatotropin antagonist
C. GH receptor antagonist (Correct Answer)
D. GH receptor agonist

Explanation: ***GH receptor antagonist*** - Pegvisomant is a **growth hormone (GH) receptor antagonist** that binds to GH receptors but does not activate them. - This action blocks the binding of endogenous GH to its receptors, thereby inhibiting the downstream production of **insulin-like growth factor 1 (IGF-1)** and reducing the symptoms of **acromegaly**. *Somatostatin antagonist* - **Somatostatin analogues** (e.g., octreotide, lanreotide) are used to treat acromegaly by inhibiting the release of growth hormone from the pituitary gland. - Pegvisomant does not act on somatostatin receptors; it functions at the level of the **GH receptor**. *Somatotropin antagonist* - **Somatotropin** is another name for **growth hormone (GH)**. - While Pegvisomant opposes the action of somatotropin, its mechanism is specifically at the receptor level, making "GH receptor antagonist" a more precise description. *GH receptor agonist* - A **GH receptor agonist** would stimulate the growth hormone receptor, leading to increased IGF-1 production and exacerbating conditions like acromegaly. - Pegvisomant has the opposite effect, blocking GH action rather than promoting it, making it an **antagonist**.

Question 720: Which of the following antithyroid medications had the maximum chances of causing agranulocytosis?

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

Explanation: ***Carbimazole*** - **Carbimazole** has the **highest reported incidence of agranulocytosis** among antithyroid drugs (approximately **0.3-0.5%**) - Although a prodrug of methimazole, **carbimazole itself** appears to confer additional risk beyond its active metabolite - **Agranulocytosis** typically occurs within the **first 2-3 months** of therapy and requires immediate discontinuation - Patients should be counseled to report **sore throat, fever, or mouth ulcers** immediately *Methimazole* - Has a **lower incidence** of agranulocytosis compared to carbimazole (approximately **0.1-0.3%**) - Once carbimazole is metabolized to methimazole, the risk profile changes - Still requires monitoring for this serious adverse effect *Propylthiouracil* - Has **comparable or slightly higher** agranulocytosis risk than methimazole but **lower than carbimazole** - More commonly associated with **hepatotoxicity** (including fulminant hepatic failure) - Preferred in **first trimester of pregnancy** and **thyroid storm** despite its risks *Iodide* - Works by **Wolff-Chaikoff effect** (inhibits thyroid hormone synthesis and release) - Does **not cause agranulocytosis** - Main adverse effects include **iodism**, hypothyroidism, and **Jod-Basedow phenomenon** (iodine-induced hyperthyroidism)

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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