Case report: finasteride-induced gynecomastia in a 62-year-old man.

The authors describe a case of bilateral (with left prevalence) gynecomastia in a 62-year-old man after finasteride treatment because of benign prostatic hypertrophy. Finasteride is an inhibitor of 5 alpha-reductase, the enzyme responsible for testosterone metabolism to dihydrotestosterone. In this patient, nonspecific endocrine alterations were found, except for a significant decrease in dihydrotestosterone levels. In addition, there were no pathologic conditions affecting other organs or pharmacologic treatments that could be responsible for gynecomastia. Drug withdrawal started a progressive reduction of the lumps until complete their disappearance. It is possible that gynecomastia was caused by alterations of estrogen/androgen ratio because of a finasteride-induced decrease in circulating dihydrotestosterone levels. In this article, the authors confirm finasteride antiandrogenic activity and recommend a close follow-up of long-term treatments with finasteride to find out other possible side effects.