Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 751: Which medication increases insulin secretion from beta cells?

A. Metformin
B. Repaglinide (Correct Answer)
C. Pioglitazone
D. Pramlintide

Explanation: ***Repaglinide*** - This medication is a **meglitinide analog** that stimulates **insulin release** from pancreatic beta cells by closing ATP-sensitive potassium channels. - Its fast onset and short duration of action make it particularly useful for controlling **postprandial glucose** excursions. *Metformin* - This medication primarily works by **decreasing hepatic glucose production** and improving insulin sensitivity in peripheral tissues. - It does **not directly stimulate insulin secretion** from beta cells; thus, it carries a lower risk of hypoglycemia compared to sulfonylureas or meglitinides. *Pramlintide* - This is an **amylin analog** that works by slowing gastric emptying, suppressing postprandial glucagon secretion, and increasing satiety. - It is an **injectable medication** used as an adjunct to insulin therapy and does not directly enhance insulin secretion from beta cells. *Pioglitazone* - This drug is a **thiazolidinedione** that improves insulin sensitivity in target tissues (e.g., muscle, fat, liver) by activating **peroxisome proliferator-activated receptor-gamma (PPAR-γ)**. - While it improves the body's response to insulin, it does **not directly stimulate insulin secretion** from the beta cells.

Question 752: Which of the antithyroid drugs inhibits iodine trapping?

A. Radioactive iodine
B. Iodides
C. Thiocyanates (Correct Answer)
D. Methimazole

Explanation: ***Thiocyanates*** - **Thiocyanates** are competitive inhibitors of the **sodium-iodide symporter (NIS)**, which is responsible for actively transporting iodide into thyroid follicular cells (iodine trapping) [1]. - By blocking NIS, thiocyanates prevent the thyroid gland from accumulating iodide, thereby inhibiting thyroid hormone synthesis [1]. *Radioactive iodine* - **Radioactive iodine (RAI)** primarily works by being taken up by thyroid cells and emitting **beta particles**, which destroy the thyroid tissue [3]. - It does not inhibit iodine trapping, but rather uses the trapping mechanism to concentrate in the thyroid and exert its destructive effect [3]. *Iodides* - **Iodides** (e.g., Lugol's solution) paradoxically inhibit organification and hormone release from the thyroid gland, an effect known as the **Wolff-Chaikoff effect** [2]. - They also decrease the vascularity and size of the thyroid gland, making them useful in preparing patients for thyroidectomy, but do not directly inhibit iodine trapping [2]. *Methimazole* - **Methimazole** is a **thionamide** drug that primarily inhibits the enzyme **thyroid peroxidase**. - This prevents the **organification of iodide** (incorporation of iodine into tyrosine residues) and the **coupling of iodotyrosines** (forming T3 and T4), not the initial trapping of iodine.

Question 753: What is the initial drug of choice for a suspected case of acute adrenal insufficiency?

A. Norepinephrine
B. Hydrocortisone (Correct Answer)
C. Dexamethasone
D. Fludrocortisone

Explanation: ***Hydrocortisone*** - This is the initial drug of choice due to its **combined mineralocorticoid and glucocorticoid activity**, which effectively replaces the deficient hormones in acute adrenal insufficiency. - It also has a **rapid onset of action** crucial for stabilizing patients in an adrenal crisis. *Norepinephrine* - This is a **vasopressor** used to manage **severe hypotension or shock** by increasing peripheral vascular resistance. - While hypotension is a feature of adrenal insufficiency, norepinephrine does not address the underlying hormonal deficiency directly and is not the primary treatment. *Dexamethasone* - Dexamethasone is a **potent glucocorticoid** and can be used in adrenal insufficiency, but it lacks significant **mineralocorticoid activity**. - Its longer half-life might make it less ideal for immediate, titratable replacement compared to hydrocortisone in an acute setting. *Fludrocortisone* - Fludrocortisone is a **pure mineralocorticoid** primarily used for long-term replacement therapy to manage sodium and potassium balance in adrenal insufficiency. - It does not have sufficient glucocorticoid activity to address the immediate, life-threatening aspects of acute adrenal crisis.

Question 754: Which of the following is an intermediate-acting insulin?

A. Insulin lispro
B. NPH insulin (Correct Answer)
C. Insulin glargine
D. Regular insulin

Explanation: ***NPH insulin*** - **NPH (Neutral Protamine Hagedorn) insulin** is characterized by its intermediate duration of action, typically peaking in 4-12 hours and lasting up to 24 hours [1]. - This intermediate profile is achieved by combining insulin with **protamine**, which slows its absorption from the subcutaneous injection site [1]. *Insulin lispro* - **Insulin lispro** is a **rapid-acting insulin** analog, designed to act very quickly after injection, typically within 15-30 minutes [1, 2]. - Its quick onset and short duration make it suitable for dosing **immediately before meals** to control post-prandial glucose levels [1]. *Regular insulin* - **Regular insulin** is a **short-acting insulin**, with an onset of action around 30-60 minutes and a peak effect typically within 2-4 hours. - It is often administered **30 minutes before meals** and can also be used intravenously in acute situations like diabetic ketoacidosis. *Insulin glargine* - **Insulin glargine** is a **long-acting insulin** analog, providing a prolonged and relatively peakless effect over 24 hours [1, 2]. - Its primary role is to provide **basal insulin coverage**, mimicking the body's continuous background insulin production [1, 2].

Question 755: Which of the following drugs acts directly to induce an erection without the need for sexual stimulation?

A. Sildenafil
B. Tadalafil
C. Alprostadil (Correct Answer)
D. Testosterone

Explanation: ***Alprostadil***- **Alprostadil** is a **prostaglandin E1** analog that can directly induce vasodilation in the penile arteries, leading to an erection without sexual stimulation [1].- It is typically administered via **intracavernosal injection** or as a **urethral suppository**.*Sildenafil*- **Sildenafil** is a **PDE5 inhibitor** that works by enhancing the effects of **nitric oxide**, which is released in response to sexual stimulation [2, 3].- It requires **sexual arousal** to be effective, as it doesn't directly initiate the erectile process [2, 3].*Tadalafil*- Similar to sildenafil, **tadalafil** is also a **PDE5 inhibitor** that works by increasing cGMP levels and promoting smooth muscle relaxation [2, 3].- Its action is dependent on the release of **nitric oxide** triggered by sexual stimulation [2, 3].*Testosterone*- **Testosterone** is a hormone involved in sex drive and overall erectile function over time, but it does not directly or acutely induce an erection.- Its primary role in erectile dysfunction is in cases of **hypogonadism**, and it requires sexual stimulation for its effects on erection.

Question 756: Which of the following has the least glucocorticoid activity?

A. Fludrocortisone
B. Cortisone (Correct Answer)
C. Dexamethasone
D. Betamethasone

Explanation: ***Cortisone*** - **Cortisone has the LEAST glucocorticoid activity** among the options listed. - It is a **prodrug** that must be converted to **hydrocortisone (cortisol)** by 11β-hydroxysteroid dehydrogenase in the liver to become active. - Its glucocorticoid potency is approximately **0.8** relative to hydrocortisone (when hydrocortisone = 1). - Due to variable hepatic conversion, it has **lower and less predictable glucocorticoid effects** compared to other agents. *Fludrocortisone* - Primarily used for its **potent mineralocorticoid activity** (125× that of hydrocortisone). - However, it retains **significant glucocorticoid activity** approximately **10-15 times** that of hydrocortisone. - Despite being marketed as a mineralocorticoid, its glucocorticoid potency is **considerably higher than cortisone**. *Dexamethasone* - **Highly potent synthetic glucocorticoid** with negligible mineralocorticoid activity. - Glucocorticoid potency is approximately **25-30 times** that of hydrocortisone. - Long duration of action (36-72 hours) and excellent CNS penetration. *Betamethasone* - **Highly potent synthetic glucocorticoid**, structurally similar to dexamethasone (differs only in stereochemistry at C-16). - Glucocorticoid potency is approximately **25-30 times** that of hydrocortisone. - Minimal mineralocorticoid activity, with similar clinical applications to dexamethasone.

Question 757: Desmopressin is preferred over vasopressin because it:

A. Is more potent and has little vasoconstrictor activity (Correct Answer)
B. Is more potent than vasopressin
C. Has little vasoconstrictor activity
D. Is more selective for V2 receptors than vasopressin

Explanation: **Is more potent and has little vasoconstrictor activity** - **Desmopressin** is a synthetic analog of **vasopressin** (ADH) that is modified to have much higher selectivity for **V2 receptors** in the renal collecting ducts, leading to potent **antidiuretic effects** [1], [3]. - This selective action results in significantly **reduced vasoconstrictor activity** (mediated by V1 receptors) compared to natural vasopressin, making it safer for clinical use to manage water balance without significant cardiovascular side effects [1], [3]. *Is more potent than vasopressin* - While desmopressin is indeed more potent in its **antidiuretic effect** due to increased affinity for **V2 receptors**, this option alone doesn't specify the critical advantage of *reduced vasoconstrictor activity* [3]. - Its superior potency alone doesn't fully explain its preference over vasopressin, as the **side-effect profile** is a major consideration. *Has little vasoconstrictor activity* - This statement is true and highlights a key advantage of desmopressin, but it omits the fact that **desmopressin is also more potent** in its desired antidiuretic effect compared to natural vasopressin [1]. - Both the **potency** and **reduced vasoconstrictor activity** contribute to its superior clinical profile [3]. *Is more selective for V2 receptors than vasopressin* - **Desmopressin's increased selectivity** for **V2 receptors** is the mechanistic basis for its preferred properties, leading to both greater antidiuretic potency and reduced vasoconstriction [1], [4]. - However, the option "Is more potent and has little vasoconstrictor activity" describes the *clinical consequences* of this selectivity, which are the direct reasons for its preferred use [2].

Question 758: Which of the following is a synthetic estrogen?

A. Estrone
B. Estriol
C. Estradiol
D. Diethylstilbestrol (Correct Answer)

Explanation: ***Diethylstilbestrol*** - **Diethylstilbestrol (DES)** is a **synthetic non-steroidal estrogen** that was historically used as a medication, particularly to prevent miscarriage. - Its use was discontinued after being linked to various adverse effects, including **vaginal clear cell adenocarcinoma** in female offspring whose mothers took DES during pregnancy. *Estrone* - **Estrone** is one of the three major **naturally occurring endogenous estrogens** in humans. - It is the primary estrogen during **menopause** and is derived from androstenedione. *Estriol* - **Estriol** is another of the three major **naturally occurring estrogens**, predominantly produced during **pregnancy** by the placenta. - It is often used as a marker for fetal well-being. *Estradiol* - **Estradiol** is the **most potent and abundant naturally occurring estrogen** in women during their reproductive years. - It plays a crucial role in the development and maintenance of female reproductive tissues and secondary sexual characteristics.

Question 759: Which of the following is a selective progesterone receptor modulator?

A. Onapristone
B. Ulipristal (Correct Answer)
C. Nomegestrol
D. Toremifene

Explanation: ***Ulipristal*** - **Ulipristal acetate** is a **selective progesterone receptor modulator (SPRM)** that acts as a progesterone receptor agonist/antagonist. - It is primarily used for **emergency contraception** and for the pre-operative treatment of **uterine fibroids**. *Onapristone* - **Onapristone** is an **antiprogestin** and a **progesterone receptor antagonist**, not a selective modulator. - It has been primarily investigated for its potential role in **breast cancer** treatment but is not approved for general clinical use. *Nomegestrol* - **Nomegestrol** is a **synthetic progestin** used in hormonal contraception. - It functions as a **progesterone receptor agonist** and does not exhibit selective modulation properties. *Toremifene* - **Toremifene** is a **selective estrogen receptor modulator (SERM)**, not a progesterone receptor modulator. - It is used in the treatment of **estrogen receptor-positive metastatic breast cancer** in postmenopausal women.

Question 760: Which steroid has the maximum mineralocorticoid activity?

A. Fludrocortisone (Correct Answer)
B. DOCA
C. Prednisolone
D. Triamcinolone

Explanation: ***Fludrocortisone*** - **Fludrocortisone** is a synthetic corticosteroid specifically designed to have potent **mineralocorticoid activity**, with significant sodium-retaining properties. - Its high affinity for **mineralocorticoid receptors** distinguishes it from other steroids and makes it effective in treating conditions like **Addison's disease** and **postural orthostatic tachycardia syndrome (POTS)** due to its ability to retain sodium and water. *DOCA (Deoxycorticosterone acetate)* - While **DOCA** does possess significant **mineralocorticoid activity** and was historically used for this purpose, **fludrocortisone** is generally considered to have a stronger and more sustained effect in clinical practice. - **DOCA's** mineralocorticoid potency is substantial but slightly less than that of **fludrocortisone** when compared on a weight basis for equivalent sodium retention. *Prednisolone* - **Prednisolone** is primarily a **glucocorticoid** with potent anti-inflammatory and immunosuppressive effects. - It has minimal to negligible **mineralocorticoid activity** and is not used for salt retention purposes. *Triamcinolone* - **Triamcinolone** is a potent **glucocorticoid** with a long duration of action and is known for its strong anti-inflammatory properties. - It has virtually no **mineralocorticoid activity**, making it unsuitable for conditions requiring sodium retention.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

Insulin and Oral Hypoglycemic Agents

Practice Questions

Adrenocorticosteroids

Practice Questions

Sex Hormones: Estrogens and Progestins

Practice Questions

Androgens and Anabolic Steroids

Practice Questions

Hormonal Contraceptives

Practice Questions

Drugs Affecting Calcium Metabolism

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Drugs for Osteoporosis

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Pharmacological Management of Obesity

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