Impact of 5-alpha reductase inhibitors on male reproductive health: A review of finasteride and dutasteride.

Androgenic alopecia (AGA), commonly known as male pattern baldness (MPB), affects a significant portion of the population, with impacts on self-esteem and quality of life. 5-alpha reductase inhibitors, including finasteride and dutasteride, are widely used treatments that increase hair density by reducing dihydrotestosterone levels. However, their effects on reproductive health remain a concern, particularly in men of reproductive age. This narrative review synthesizes current clinical and experimental evidence on the reproductive effects of 5-alpha reductase inhibitors. Relevant studies were identified through a review of published literature, including randomized controlled trials, observational studies, and mechanistic investigations. Outcomes of interest included sperm parameters, hormonal profiles, sexual function, and potential long-term reproductive effects. Across studies, finasteride and dutasteride were associated with reductions in sperm count (34% with finasteride, 29% with dutasteride), sperm concentration, and motility. Hormonal alterations included, increased testosterone levels, and variable changes in dihydrotestosterone, estradiol, progesterone and androstenedione levels. Findings related to sexual dysfunction were variable, with some demonstrating persistent decreased libido, erectile dysfunction, and reduced penile sensitivity, months to years after discontinuation. Mechanistic studies in rodents revealed significant reductions in the expression of genes critical to spermatogenesis (Dazl, Prm2, Sycp3, Tsga10) and alterations in penile tissue contractility and nitric oxide synthase signaling, providing potential explanations for these reproductive effects. Overall, while 5-alpha reductase inhibitors are effective treatments for AGA, they may adversely affect reproductive parameters in a subset of patients. While current evidence focuses primarily on single drug regimens, the growing use of combination therapies targeting multiple 5-alpha reductase isotypes raises the potential for additive or synergistic reproductive effects. Given the variability in outcomes and limited long-term data, further research is needed to better characterize these risks, particularly in younger populations and with combination therapies.