EFFECT OF FINASTERIDE ON ADRENAL STEROIDOGENESIS IN MEN

Finasteride, a 5 alpha-reductase inhibitor, does not bind to the andro gen receptor and has no other known hormonal activity. To determine wh at effect, if any, it has on adrenal steroidogenesis, 10 healthy men r eceived 5 mg finasteride daily for 28 days. Adrenocorticotropic hormon e (ACTH) stimulation tests were performed before and after 4 weeks of finasteride administration (5 mg daily). Serum levers of 17-hydroxypre gnenotone, 17-hydroxyprogesterone, deoxycorticosterone, corticosterone , aldosterone, cortisol, dehydroepiandrosterone, and androstenedione w ere measured before and 60 minutes after i.v. ACTH. Finasteride decrea sed serum dihydrotestosterone levels from 31 +/- 5 to 4.4 +/- 1.2 ng/d l (P < 0.001). There were no significant changes in basal or ACTH-stim ulated serum levels of adrenal steroids. There was also no significant decrease in the product to precursor ratio for the seven adrenal enzy mes tested. Finasteride increased mean serum androstenedione levels by 17% (P = 0.10) and significantly increased the androstenedione to 17- hydroxyprogesterone ratio (P = 0.02 before ACTH and 0.05 after ACTH). These changes are most likely due to inhibition of androstenedione met abolism by 5 alpha-reductase. In conclusion, finasteride has no detect able effect on adrenal steroidogenesis, other than that which can be e xplained by inhibition of the 5 alpha-reductase enzyme.