5-alpha-reductase inhibitors are associated with increased sexual adverse events in androgenetic alopecia patientsHair loss medications may cause some side effects for men

5α-reductase inhibitors (5-ARIs) are most commonly used to treat benign prostatic hyperplasia (BPH) and androgenetic alopecia (AGA). Preclinical and clinical studies suggest that in patients with AGA treated with 5-ARIs, a subset reports sexual adverse events, including decreased libido, erectile dysfunction, and ejaculatory disorders. This review explores the development of sexual dysfunction in patients with androgenetic alopecia due to the use of 5-ARIs, emphasizing their importance in the clinical diagnosis of health disorders coexisting with hair loss. A systematic review was conducted by searching electronic databases, including MEDLINE, Scopus, Web of Science and Google Scholar, according to the PRISMA guidelines. The search was limited to articles published in English and up to December 2025. Key search terms included “5α-reductase inhibitors” or “5-ARIs” or “finasteride” or “dutasteride” AND “side effects” or “sexual side effects” or “sexual” or “sexual dysfunction” AND “androgenetic alopecia” or “male pattern hair loss” or “female pattern hair loss.” Data synthesis included findings from 41 studies, comprising 33 primary-evidence studies in AGA/MPHL/FPHL populations and 8 supporting-evidence studies providing pharmacokinetic, mixed-indication, or comparative context. 5-ARIs are effective therapies for androgenetic alopecia and are generally well tolerated. Across placebo-controlled RCTs evaluating oral finasteride 1 mg in men with AGA, sexual adverse events were reported in 1.9–6.7% of treated patients compared with 0.9–3.9% in placebo groups, with most events mild and reversible upon discontinuation. Topical finasteride 0.25% was associated with lower rates of sexual adverse events (2.8%) compared with oral finasteride (4.8%). For dutasteride 0.5 mg, sexual adverse events ranged from 4.1 to 12.0% across RCTs, compared with 4.0–5.0% in placebo groups. No sexual adverse effects were consistently reported in women treated with 5-ARIs for AGA. In most reports, the effects were transient and reversible after discontinuation. Overall, clinicians should counsel patients that most sexual side effects reported in controlled AGA studies are infrequent, mild, and reversible, but individual susceptibility varies. Shared decision-making, careful monitoring of sexual function, and further high-quality long-term studies—using standardized definitions of sexual dysfunction and persistence—are needed to quantify risks better and identify vulnerable subgroups.