Effect of finasteride on serum levels of androstenedione, testosterone and their 5α-reduced metabolites in men at risk for prostate cancer

► Treatment of men with finasteride is used for primary prevention of prostate cancer. ► Finasteride suppresses serum DHT levels. ► Effect of finasteride on DHT precursors/metabolites in men was studied during 1 year. ► DHT sulfate (DHT S) and androstanediol glucuronide were suppressed, similar to DHT. ► DHT S, a novel metabolite, may serve as an important marker of 5α-reductase inhibition.