5α-Reductase Inhibitors (5ARIs) and Male Reproduction

The document from 2017 reviews the effects of 5α-Reductase Inhibitors (5ARIs), specifically finasteride and dutasteride, on male reproduction. These drugs are used to treat benign prostate hyperplasia (BPH) and lower urinary tract symptoms, and at lower doses, they are used to treat male hair loss by inhibiting the conversion of testosterone to dihydrotestosterone (DHT). While testosterone levels remain relatively stable, DHT levels can be reduced by up to 90% in men taking these medications. The document reports that 5ARIs are known to negatively impact libido, erectile function, and ejaculation, with a meta-analysis indicating an odds ratio of ejaculatory dysfunction of 3 for both finasteride and dutasteride. Regarding semen quality, while most men remain within the normal range, some studies have reported a decrease in total sperm count and motility, with a small subset of men experiencing a significant reduction to less than 10% of baseline values. This effect seems to be reversible upon discontinuation of the drug. The lower doses of finasteride used for treating male-pattern baldness appear to have little effect on semen quality in men with normal semen, but there are reports of negative effects on sperm numbers in men with oligozoospermia. The document concludes that while most men taking 5ARIs for BPH will experience only small negative effects on semen quality, some may be profoundly affected, and more studies are needed to assess fertility endpoints in 5ARI-treated men.