Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 801: 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.

Question 802: All of the following are side effects of growth hormone supplementation therapy except

A. Slipped capital femoral epiphysis
B. Pseudotumour cerebri
C. Hypoglycemia (Correct Answer)
D. Arthralgia

Explanation: ***Hypoglycemia*** - Growth hormone (GH) has an **anti-insulin effect**, increasing **insulin resistance** and hepatic glucose production, leading to **hyperglycemia** rather than hypoglycemia. - This diabetogenic effect contributes to a higher risk of developing **impaired glucose tolerance** and **type 2 diabetes mellitus** in individuals receiving long-term GH therapy. - GH is a **counter-regulatory hormone** that opposes insulin action. *Slipped capital femoral epiphysis* - Growth hormone supplementation can accelerate linear growth, which increases the risk of **mechanical stress** on the growth plate. - This rapid growth can lead to **weakening and displacement of the femoral capital epiphysis**, particularly in prepubertal and pubertal children. - This is a recognized orthopedic complication requiring monitoring during GH therapy. *Arthralgia* - Joint pain and stiffness are **common side effects** of GH therapy, affecting up to 25% of patients. - Related to **fluid retention** and **soft tissue swelling** caused by GH's effects on sodium and water retention. - May be accompanied by **myalgia** (muscle pain) and **carpal tunnel syndrome**. *Pseudotumour cerebri* - Also known as **benign intracranial hypertension**, this rare but serious side effect involves increased intracranial pressure without a tumor. - Presents with **headache, visual disturbances**, and **papilledema**. - Mechanism may involve alterations in **cerebrospinal fluid dynamics** and **increased CSF production** induced by GH.

Question 803: Which of the following statements about clomiphene citrate is true?

A. Enclomiphene has antiestrogenic effects. (Correct Answer)
B. The risk of multiple pregnancies is less than 1%.
C. It is contraindicated in male hypogonadism.
D. The chance of pregnancy is modestly increased compared to placebo.

Explanation: ***Enclomiphene has antiestrogenic effects.*** - Clomiphene citrate is a racemic mixture of two stereoisomers, **enclomiphene** (trans-isomer) and **zuclomiphene** (cis-isomer). - **Enclomiphene** is the more potent antiestrogenic isomer, which blocks estrogen receptors in the hypothalamus and pituitary, leading to increased **gonadotropin-releasing hormone (GnRH)** secretion and subsequent **follicle-stimulating hormone (FSH)** and **luteinizing hormone (LH)** release. - This mechanism is responsible for its effectiveness in inducing ovulation. *The chance of pregnancy is modestly increased compared to placebo.* - This is **incorrect** - Clomiphene citrate **significantly** increases the chances of ovulation and pregnancy in anovulatory women, representing much more than a modest increase. - Studies show substantial improvement in ovulation rates (70-80%) and live birth rates (30-40%) with clomiphene compared to placebo in women with anovulatory infertility. *The risk of multiple pregnancies is less than 1%.* - This is **incorrect** - The risk of multiple pregnancies with clomiphene citrate is actually **5-10%**, primarily twins (5-8%), with less than 1% for triplets or higher-order multiples. - This represents a significant increase compared to spontaneous conception rates (~1-2% twins naturally). *It is contraindicated in male hypogonadism.* - This is **incorrect** - Clomiphene citrate is actually used **off-label** in men with **hypogonadism** to stimulate endogenous testosterone production. - In men, it works by blocking estrogen receptors at the hypothalamic-pituitary level, leading to increased GnRH, LH, and FSH secretion, which stimulates **Leydig cells** to produce testosterone and **Sertoli cells** to support spermatogenesis.

Question 804: Which of the following preparations of insulin is long-acting?

A. Lispro
B. Detemir (Correct Answer)
C. NPH
D. Aspart

Explanation: ***Detemir*** - **Detemir** is a **long-acting insulin analog** that provides a relatively peakless and prolonged basal insulin effect, typically lasting **up to 24 hours**. - Its prolonged action is due to fatty acid chain binding to **albumin**, which slows its absorption and degradation. - Classified as true **long-acting insulin** in modern pharmacological classification. *Lispro* - **Lispro** is a **rapid-acting insulin analog** with a quick onset (15-30 minutes) and short duration of action (3-5 hours), typically taken just before meals. - Its rapid action results from a genetic modification that prevents **hexamer formation**, allowing for quicker absorption. *Aspart* - **Aspart** is another **rapid-acting insulin analog**, similar to lispro, with a fast onset (10-20 minutes) and short duration (3-5 hours), making it suitable for bolus dosing with meals. - Its rapid absorption is due to replacing **proline** with **aspartic acid** at position B28, which reduces self-association. *NPH* - **NPH (Neutral Protamine Hagedorn)** is an **intermediate-acting insulin** preparation with an onset of 1-4 hours and a duration of 10-18 hours. - Its extended action is achieved by combining insulin with **protamine** and **zinc**, forming a suspension that slowly dissolves. - Despite its relatively long duration, NPH is **not classified as long-acting** in modern insulin taxonomy—true long-acting insulins (Detemir, Glargine) have longer, more peakless profiles.

Question 805: Which of the following drugs does not cause pharmacological adrenalectomy?

A. Mitotane
B. Methotrexate (Correct Answer)
C. Ketoconazole
D. Aminoglutethimide

Explanation: ***Methotrexate*** - **Methotrexate** is an **antimetabolite** and **folate antagonist** primarily used in chemotherapy and for autoimmune diseases. It does not exert its primary action on the adrenal gland or steroid synthesis. - Its mechanism involves inhibiting **dihydrofolate reductase**, leading to reduced DNA synthesis and cell proliferation, which is unrelated to adrenal function. *Ketoconazole* - **Ketoconazole** is an antifungal agent that inhibits several **cytochrome P450 enzymes** involved in steroidogenesis, including 17α-hydroxylase and 11β-hydroxylase. - This inhibition leads to a decrease in **cortisol and androgen synthesis**, effectively causing a pharmacological adrenalectomy. *Mitotane* - **Mitotane** is a cytotoxic agent that causes **adrenocortical atrophy** and inhibits the synthesis of adrenal steroids. - It is specifically used in the treatment of **adrenocortical carcinoma** due to its direct destructive effect on adrenal cells. *Aminoglutethimide* - **Aminoglutethimide** inhibits the enzymatic conversion of **cholesterol to pregnenolone**, the rate-limiting step in steroid hormone synthesis. - This broad inhibition reduces the production of **all adrenal steroids**, including cortisol, thus inducing a pharmacological adrenalectomy.

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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