Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 791: Which of the following is the drug of choice for the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)?

A. Vasopressin
B. Thiazide diuretic
C. Chlorpropamide
D. Demeclocycline (Correct Answer)

Explanation: ***Demeclocycline*** - **Demeclocycline** is a **tetracycline antibiotic** that induces **nephrogenic diabetes insipidus**, making the renal tubules less responsive to ADH. - This effect helps in treating SIADH by promoting water excretion and correcting **hyponatremia**. *Vasopressin* - **Vasopressin** (ADH) is the hormone that is excessively secreted in SIADH, leading to water retention. - Administering vasopressin would **aggravate** SIADH symptoms by increasing water reabsorption. *Thiazide diuretic* - **Thiazide diuretics** can worsen hyponatremia in SIADH by causing **sodium loss** and **reducing free water clearance**. - Volume depletion from thiazides can paradoxically enhance ADH activity, making them contraindicated in SIADH. *Chlorpropamide* - **Chlorpropamide** is a **sulfonylurea** that can actually **potentiate ADH action**, thereby worsening SIADH. - It works by increasing the sensitivity of renal tubules to vasopressin, which is counterproductive in SIADH management.

Question 792: Precocious puberty is treated by administering

A. Oestrogen
B. Gonadotropin-Releasing Hormone (GnRH)
C. LHRH analogs (e.g., Leuprolide) (Correct Answer)
D. Testosterone

Explanation: ***LHRH analogs (e.g., Leuprolide)*** - **LHRH analogs** (GnRH agonists) are the standard treatment for central precocious puberty through continuous, non-pulsatile stimulation of the pituitary. - This leads to **downregulation and desensitization** of GnRH receptors, effectively suppressing gonadotropin (LH and FSH) release. - Suppression halts progression of pubertal development, preventing further development of **secondary sexual characteristics** and preserving final adult height potential. *Oestrogen* - Administering **oestrogen** would worsen precocious puberty by accelerating the development of secondary sexual characteristics and advancing bone age. - Oestrogen is a primary hormone responsible for female pubertal changes, so exogenous administration would **exacerbate** the condition. *Gonadotropin-Releasing Hormone (GnRH)* - Native **GnRH** is not used for treatment because it requires **pulsatile administration** to maintain normal function, which would stimulate (not suppress) gonadotropin release. - Without the continuous receptor exposure that causes downregulation, native GnRH would promote rather than suppress pubertal progression. - Treatment requires **GnRH agonists (LHRH analogs)** that provide sustained receptor stimulation leading to desensitization. *Testosterone* - Administering **testosterone** would accelerate precocious puberty, especially in males, leading to early development of male secondary sexual characteristics. - Testosterone would advance bone age prematurely, potentially compromising the child's **final adult height**.

Question 793: What is the primary condition for which calcitriol is used as a treatment?

A. Pemphigus
B. Secondary hyperparathyroidism (Correct Answer)
C. Lichen planus
D. Leprosy

Explanation: Secondary hyperparathyroidism - Calcitriol is the active form of vitamin D (1,25-dihydroxyvitamin D₃), and it is crucial for regulating calcium and phosphate levels in the body [1]. - In secondary hyperparathyroidism, often seen in chronic kidney disease (CKD), the kidneys cannot convert vitamin D to its active form, leading to hypocalcemia and increased PTH secretion [1], [2]. - Calcitriol supplementation helps to increase calcium absorption from the gut and suppress the release of parathyroid hormone (PTH), thereby treating the underlying cause of secondary hyperparathyroidism [1], [2]. - This is the primary therapeutic indication for calcitriol in clinical practice. Lichen planus - This is a chronic inflammatory condition affecting the skin, hair, nails, and mucous membranes - Typically treated with corticosteroids or other immunosuppressants - Calcitriol has no primary role in the treatment of lichen planus; its therapeutic applications are predominantly related to calcium and bone metabolism Pemphigus - Pemphigus is a group of rare autoimmune blistering diseases that affect the skin and mucous membranes - Primary treatment involves immunosuppressants like corticosteroids, often in high doses - Calcitriol is not indicated for the treatment of pemphigus, as its mechanism of action is unrelated to the autoimmune processes characteristic of this disease Leprosy - Leprosy is a chronic infectious disease caused by the bacterium Mycobacterium leprae - Treated with multi-drug therapy (MDT), which includes antibiotics like rifampicin, dapsone, and clofazimine - Calcitriol is not an antibiotic and therefore has no role in treating the bacterial infection responsible for leprosy

Question 794: Which of the following is preferred for infertility treatment of a female with increased prolactin levels?

A. Dopamine
B. Carbidopa
C. Cabergoline (Correct Answer)
D. Bromocriptine

Explanation: ***Cabergoline*** - **Cabergoline** is a **dopamine agonist** that is highly effective in normalizing prolactin levels and restoring fertility in women with hyperprolactinemia. - It has a **longer half-life** and is generally associated with **fewer side effects** compared to other dopamine agonists, allowing for less frequent dosing (once or twice weekly). *Dopamine* - While **dopamine** itself is the natural inhibitor of prolactin secretion, it has a **very short half-life** and cannot be administered orally as a long-term treatment. - It is typically used as an IV pressor agent in critical care and is not suitable for treating chronic hyperprolactinemia. *Carbidopa* - **Carbidopa** is a **decarboxylase inhibitor** used to prevent the peripheral metabolism of levodopa, allowing more levodopa to reach the brain. - It is primarily used in the treatment of **Parkinson's disease** and has no direct role in lowering prolactin levels. *Bromocriptine* - **Bromocriptine** is also a **dopamine agonist** used to treat hyperprolactinemia, but it typically requires **daily dosing** and is associated with a higher incidence of side effects like nausea and dizziness. - While effective, **cabergoline** is generally preferred due to its better tolerability and convenience.

Question 795: Metyrosine is used in the treatment of?

A. Pheochromocytoma (Correct Answer)
B. Cushing syndrome
C. Addison's disease
D. Acromegaly

Explanation: ***Pheochromocytoma*** - **Metyrosine** inhibits **tyrosine hydroxylase**, the rate-limiting enzyme in **catecholamine synthesis**, thus reducing the production of **epinephrine** and **norepinephrine**. - Its primary use is in the preoperative management of **pheochromocytoma** to prevent **hypertensive crises** during surgery, and in patients with inoperable or metastatic disease to control symptoms. *Acromegaly* - **Acromegaly** is characterized by excessive **growth hormone** production. - Treatment typically involves **somatostatin analogs**, **GH receptor antagonists**, or surgery, not metyrosine. *Cushing syndrome* - **Cushing syndrome** results from prolonged exposure to **high cortisol levels**. - Management focuses on reducing **cortisol** production or surgical removal of the underlying cause, not primarily involving metyrosine. *Addison's disease* - **Addison's disease** is caused by **adrenal insufficiency** leading to deficient **cortisol** and **aldosterone**. - Treatment involves **hormone replacement therapy** with glucocorticoids and mineralocorticoids.

Question 796: Which oral drug is effective for the treatment of acromegaly?

A. Bromocriptine
B. Octreotide
C. Cabergoline (Correct Answer)
D. Growth hormone receptor antagonist

Explanation: ***Cabergoline*** - **Cabergoline** is an oral **dopamine agonist** that can effectively suppress growth hormone (GH) secretion in a significant subset of acromegaly patients, particularly those with co-secretion of prolactin [1]. - It works by stimulating **dopamine D2 receptors** on pituitary somatotrophs, leading to a reduction in GH production [1]. *Octreotide* - **Octreotide** is a **somatostatin analog** administered via **injection** (subcutaneously or intramuscularly), not orally [3]. - Although highly effective in treating acromegaly by inhibiting GH release, its parenteral route of administration makes it unsuitable for an oral drug question [3]. *Growth hormone receptor antagonist* - **Growth hormone receptor antagonists** like **pegvisomant** act by blocking the action of GH at its receptor, but they are administered via **subcutaneous injection** [2]. - While effective in normalizing IGF-1 levels, they do not reduce GH secretion and are not available in oral form [2]. *Bromocriptine* - **Bromocriptine** is an older, first-generation **dopamine agonist** that can be taken orally [1]. - While it may lower GH levels in some acromegaly patients, its efficacy is generally **less potent and sustained** compared to cabergoline, making it a less preferred choice for primary treatment [1].

Question 797: What is the drug of choice for central diabetes insipidus?

A. Desmopressin (Correct Answer)
B. Leuprolide
C. Insulin
D. Thiazide diuretics

Explanation: ***Desmopressin*** - **Desmopressin** is a synthetic analog of **vasopressin (ADH)** that selectively acts on V2 receptors in the kidney [1]. - It effectively replaces the deficient ADH in central diabetes insipidus, reducing urine output and increasing urine osmolality [1]. *Leuprolide* - **Leuprolide** is a **GnRH agonist** used to treat conditions like prostate cancer, endometriosis, and precocious puberty. - It has no role in the management of diabetes insipidus as it does not affect ADH production or action. *Thiazide diuretics* - While seemingly counterintuitive, **thiazide diuretics** are sometimes used in **nephrogenic diabetes insipidus** to reduce polyuria. - They are not the drug of choice for central diabetes insipidus because they do not address the primary deficiency of ADH. *Insulin* - **Insulin** is a hormone used to treat **diabetes mellitus**, a condition characterized by high blood glucose levels. - It has no relevance to either central or nephrogenic diabetes insipidus, which are disorders of water balance.

Question 798: Which of the following drugs is contraindicated in patients with diabetes and is used for the treatment of insulinoma?

A. Nicorandil
B. Minoxidil
C. Hydralazine
D. Diazoxide (Correct Answer)

Explanation: ***Diazoxide*** - **Diazoxide** is an **arteriolar vasodilator** that also has a potent **hyperglycemic** effect by **opening K-ATP channels** in pancreatic beta cells, which **inhibits insulin secretion**. - This mechanism makes it the drug of choice for treating **insulinoma** (where excess insulin causes hypoglycemia), but it is **absolutely contraindicated in diabetics** due to its severe hyperglycemic action. - It is the only drug among the options that satisfies both criteria: used for insulinoma AND contraindicated in diabetes. *Nicorandil* - **Nicorandil** is a **potassium channel activator** and nitrate derivative that causes vasodilation, primarily used for **angina pectoris**. - It does not inhibit insulin secretion or cause clinically significant hyperglycemia that would contraindicate its use in diabetes. - Not used for insulinoma treatment. *Minoxidil* - **Minoxidil** is a potent direct **arteriolar vasodilator** primarily used for **severe refractory hypertension** and topically for **alopecia** (hair loss). - While it can occasionally cause minor glucose intolerance, it is not contraindicated in diabetes and has no role in insulinoma treatment. *Hydralazine* - **Hydralazine** is a direct **arteriolar vasodilator** used to treat **hypertension**, particularly in pregnancy (preeclampsia/eclampsia). - It does not have significant effects on glucose metabolism or insulin secretion and is not used for insulinoma treatment.

Question 799: Which of the following is the synthetic form of Triiodothyronine (T3)?

A. Liothyronine sodium (Correct Answer)
B. Levothyroxine sodium
C. Liotrix
D. Propylthiouracil

Explanation: ***Liothyronine sodium*** - This is the **synthetic form of Triiodothyronine (T3)**, the more potent and active form of thyroid hormone. - It has a **rapid onset of action** (within a few hours) and shorter half-life compared to T4. - Used in cases where direct T3 replacement is needed, such as in **myxedema coma** or for suppression testing. *Levothyroxine sodium* - This is the synthetic form of **Thyroxine (T4)**, which is then converted to T3 in peripheral tissues. - It is the **most common preparation** for treating hypothyroidism due to its longer half-life (7 days) and stable serum levels. *Liotrix* - Liotrix is a **combination preparation of synthetic T4 and synthetic T3**, typically in a 4:1 ratio. - It aims to mimic the natural physiological ratio; however, its use is **less common** than levothyroxine monotherapy. *Propylthiouracil* - This is an **antithyroid drug** used to treat hyperthyroidism, not a thyroid hormone replacement. - It works by inhibiting thyroid peroxidase and peripheral conversion of T4 to T3.

Question 800: Which of the following is a testosterone inhibitor?

A. Spironolactone (Correct Answer)
B. Clomiphene
C. Bremelanotide
D. Sildenafil

Explanation: ***Spironolactone*** - Spironolactone is an **androgen receptor antagonist** and also inhibits **testosterone synthesis** by blocking 17α-hydroxylase and 17,20-lyase enzymes. - This dual action reduces the effects and production of testosterone, making it useful in conditions like **hirsutism** and **polycystic ovary syndrome (PCOS)**. *Clomiphene* - Clomiphene is a **selective estrogen receptor modulator (SERM)** that acts as an antagonist in the hypothalamus, thereby increasing the pulsatile release of GnRH. - This leads to increased FSH and LH secretion, stimulating **ovulation in women** and **testosterone production in men**, rather than inhibiting testosterone. *Bremelanotide* - Bremelanotide is a **melanocortin receptor agonist** that acts on the central nervous system to increase sexual desire. - It is used to treat **hypoactive sexual desire disorder (HSDD)** in premenopausal women and has no direct effect on testosterone levels or action. *Sildenafil* - Sildenafil is a **phosphodiesterase-5 (PDE5) inhibitor** that increases blood flow to the penis by enhancing the effects of nitric oxide, leading to an erection. - It is primarily used to treat **erectile dysfunction** and does not directly inhibit testosterone.

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

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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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