Endocrine Pharmacology — MCQs

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

Detemir. ***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.

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

Enclomiphene has antiestrogenic effects. ***Enclomiphene has antiestrogenic effects*** - **Enclomiphene** is the trans-isomer of clomiphene citrate and acts as a **selective estrogen receptor antagonist** at hypothalamic estrogen receptors. - Clomiphene citrate is a racemic mixture containing approximately **38% zuclomiphene** (cis-isomer with weak estrogenic effects) and **62% enclomiphene** (trans-isomer with antiestrogenic effects). - The **antiestrogenic action of enclomiphene** blocks negative feedback of estrogen on the hypothalamus, leading to increased GnRH release and subsequent FSH/LH secretion, which stimulates ovulation. - This statement is **medically accurate and true**. *Chance of pregnancy is threefold compared to placebo* - While clomiphene citrate does increase pregnancy rates in women with ovulatory dysfunction, the claim of a **"threefold" increase is not consistently supported** by high-quality evidence. - Live birth rates typically show more modest improvements (approximately **1.5-2x**) compared to expectant management. - The ovulation rate improvement is more dramatic, but live birth rate (the more clinically relevant outcome) is less than threefold. *Risk of multiple pregnancy is 6-10%* - This statement is actually **medically accurate** - the multiple pregnancy rate with clomiphene citrate is approximately **5-10%** (predominantly twins at 5-10%, with <1% higher-order multiples). - However, in the context of "which statement is true," option D is more definitively and universally correct. *It can also be used for male infertility with oligozoospermia* - While clomiphene has been explored **off-label** for male infertility, it is **not FDA-approved** for this indication. - Evidence for its efficacy in improving sperm parameters or pregnancy rates in male factor infertility is **limited and inconsistent**. - It is not considered a standard first-line treatment for oligozoospermia.

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

Methotrexate. ***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.

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