BH02 Reversibility of 5-alpha reductase inhibitor effects on semen parameters: a review of human evidence

Abstract

The 5α-reductase inhibitors (5-ARIs), finasteride and dutasteride, are widely prescribed for androgenetic alopecia. Despite their established efficacy, concerns persist regarding potential adverse effects on male reproductive function. Published data on semen parameters and fertility outcomes are heterogeneous, and uncertainty remains regarding the reversibility and clinical significance of reported changes, particularly with long-term use. We aimed to synthesize human evidence evaluating the effects of finasteride and dutasteride on semen parameters and gonadotrophins during treatment and following discontinuation, with particular attention to dose, treatment duration and reversibility. A systematic literature search of PubMed, Scopus and the Cochrane Library was performed to identify human studies reporting semen outcomes in men exposed to 5-ARIs. Eligible studies included randomized controlled trials, cohort studies and case reports evaluating finasteride 1 mg or 5 mg and dutasteride 0.5 mg. Data were extracted on semen volume, sperm concentration, motility, morphology, total sperm number and gonadotrophins (follicle-­stimulating hormone and luteinizing hormone). Due to heterogeneity in study design and reporting, the findings were synthesized narratively. Finasteride consistently produced modest reductions in semen volume, sperm concentration and total sperm number, which were typically reversible following discontinuation. In healthy men, finasteride 1 mg resulted in minimal or no clinically meaningful changes, while higher doses (5 mg) were associated with transient reductions in sperm motility that generally remained within WHO reference ranges. Dutasteride demonstrated more pronounced effects, including greater declines in semen volume, motility and total sperm number, with prospective data suggesting incomplete recovery following treatment durations exceeding approximately 18–20 months. Sperm morphology was largely preserved with both agents. Gonadotrophin levels remained stable across studies, indicating preserved hypothalamic–pituitary function. Case reports frequently described substantial improvement in semen parameters after finasteride cessation, including reversal of severe oligospermia or azoospermia. Finasteride causes mild, reversible semen changes, while prolonged dutasteride use may impair recovery, warranting caution in men planning conception.