Recent postmarketing studies and the [FDA] have found that finasteride, 1 mg, for androgenic alopecia has been associated with persistent sexual and nonsexual adverse effects. The present study was designed to assess whether otherwise healthy former users of finasteride with persistent sexual adverse effects have a higher prevalence of low serum androgens and spermatogenic deficits.… 3 of 19 participants (16%) [had] severe oligospermia (<5 million/mL). The mean and median motilities were 50% (23%) and 50%, respectively, with 4 of 9 participants (44%) having 2 confirmed low motility.
Irwig MS. Androgen levels and semen parameters among former users of finasteride with persistent sexual adverse effects. JAMA Dermatol. 2014 Dec;150(12):1361-3. doi: 10.1001/jamadermatol.2014.1830. [PubMed]