Finasteride therapy in benign prostatic hyperplasia produces its benefit through which mechanism, and what is its expected effect on serum PSA?
- A Inhibition of 5-alpha reductase type II; lowers PSA by approximately 50 percent ✓
- B Androgen receptor blockade; raises PSA by 50 percent
- C GnRH receptor downregulation; leaves PSA unchanged
- D Inhibition of aromatase; lowers PSA by approximately 90 percent
Correct answer: A. Inhibition of 5-alpha reductase type II; lowers PSA by approximately 50 percent
Explanation
Finasteride selectively inhibits the type II isoenzyme of 5-alpha reductase, blocking conversion of testosterone to dihydrotestosterone, the trophic hormone for prostatic epithelium, leading to shrinkage of the gland. Because DHT drives PSA expression, serum PSA falls by about half after a year of therapy, and measured values must be doubled when screening for prostate cancer during treatment. It is not an androgen receptor antagonist, which distinguishes it from bicalutamide.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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