... .Recognized side effects, experienced by around >1% of users, include erectile dysfunction, and less often gynecomastia ... a 5-year study of men with mild to moderate hair loss, 48% of those treated with Propecia ... the placebo group, for all five years of the study. Propecia is effective only for as long ... However, Propecia's supporters respond that the study was on post-menopausal women whose hair loss ...