Conversion of testosterone to dihydrotestosterone by the enzyme 5α-reductase is required for the following actions except:

Correct Answer: D

Rationale: Testosterone is converted to dihydrotestosterone by the enzyme 5α-reductase, which is involved in various physiological processes in males. However, spermatogenesis does not directly depend on dihydrotestosterone. Spermatogenesis is primarily regulated by follicle-stimulating hormone (FSH) and luteinizing hormone (LH). While testosterone plays a role in supporting spermatogenesis, dihydrotestosterone specifically is not required for this process. Therefore, the conversion of testosterone to dihydrotestosterone by 5α-reductase is not directly involved in spermatogenesis.

Correct Answer: C

Rationale: Finasteride is a 5-alpha reductase inhibitor that primarily reduces the static component of urinary obstruction in benign prostatic hyperplasia (BPH) by decreasing the size of the prostate gland. It inhibits the conversion of testosterone to dihydrotestosterone (DHT), which is responsible for prostate growth. Finasteride takes more than 3 months to exert its beneficial effect as it gradually reduces the size of the prostate gland. It is typically prescribed for long-term management of BPH symptoms. Tamsulosin and Terazosin, both alpha-1 blockers, primarily target the dynamic component of urinary obstruction by relaxing smooth muscle in the prostate and bladder neck, providing rapid symptom relief. Amphetamine is not used in the treatment of BPH.

Correct Answer: B

Rationale: Finasteride is a steroid 5α-reductase inhibitor that has been found useful in treating benign prostatic hypertrophy (BPH) and male pattern baldness. By inhibiting the enzyme 5α-reductase, finasteride reduces the conversion of testosterone to dihydrotestosterone (DHT), which is implicated in both conditions. In BPH, DHT contributes to prostate enlargement, while in male pattern baldness, it contributes to the miniaturization of hair follicles. Finasteride helps in reducing DHT levels, leading to improvements in both conditions. It is a well-established and commonly prescribed medication for these purposes.

Correct Answer: A

Rationale: Estrogens are known to have various metabolic actions in the body, but they do not typically promote anabolism. Instead, estrogens have been shown to have effects such as improving insulin sensitivity and promoting a favorable lipid profile by decreasing LDL-cholesterol and increasing HDL-cholesterol levels. Estrogens are also associated with salt and water retention, which can contribute to bloating and weight gain in some individuals. Additionally, estrogens can lead to impaired glucose tolerance, especially at higher doses or in individuals with existing metabolic issues. However, the promotion of anabolism is not a characteristic metabolic action of estrogens.

Correct Answer: B

Rationale: Estrogen replacement therapy in menopausal women has been associated with an increased risk of endometrial carcinoma due to unopposed estrogen stimulation. Adding a progestin for 10-12 days each month helps to counteract this risk by providing progestational support, which protects the endometrium from estrogen-induced hyperplasia and potential malignant transformation. This combination therapy is known as hormone replacement therapy and is commonly recommended to reduce the risk of endometrial carcinoma in menopausal women receiving estrogen therapy.