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Men using finasteride to treat baldness had a dramatic increase in sperm count following discontinuation of the drug, according to a review of records at male infertility clinic.

Average sperm count increased fourfold (and by as much as 12-fold) when the men stopped using the low-dose finasteride product, according to , of Mount Sinai Hospital and the University of Toronto, and co-authors. None of the patients had a decrease in sperm count after stopping finasteride.

Discontinuation of the drug did not affect hormone parameters, sperm motility, or sperm morphology, they reported online in .

"Our study indicates that finasteride is associated with subfertility in some men and that the adverse effect of finasteride is reversible for most of the men who present with infertility," the authors concluded. "We suggest that in infertile men with oligospermia or azoospermia using finasteride, even at the low dose of 1 mg for androgenic alopecia, the drug should be discontinued.

"The discontinuation of finasteride may not bring the sperm parameters to levels where a spontaneous pregnancy is likely, but it may lead to improvement in semen parameters that will allow for less invasive fertility therapy."

Initially approved for treatment of benign prostatic hyperplasia (BPH), finasteride has been approved for male-pattern baldness for more than 15 years. The newer application has resulted in greater use of the drug, albeit in lower doses, by reproductive-age men.

A member of the , finasteride increases the ratio of testosterone to dihydrotestosterone (DHT). Though androgens are essential to spermatogenesis, the relative contributions of testosterone and DHT are unknown, the authors noted.

Few studies have examined the effects of finasteride on male fertility, and most of those have comprised small patient series. The 5-mg dose of finasteride used to treat BPH has a reversible negative effect on semen parameters. The 1-mg dose has been shown to have no negative effect on healthy men with normal spermatogenesis, but a few case reports have described impaired spermatogenesis, which was reversed after discontinuation of the drug.

To expand the investigation of finasteride and spermatogenesis beyond case reports, Jarvi and colleagues reviewed records of men who underwent fertility evaluations during 2008 to 2012. They excluded men who had obstructive azoospermia or primary testicular failure.

Laboratory studies included serum testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol. Semen samples were obtained at least 48 hours after the last ejaculation but not more than 7 days afterward.

Of 4,400 men seen at the clinic, 27 (0.6%) were taking finasteride 1 mg/d for alopecia areata. The study population had several conditions pertinent to the examination: six had varicoceles, two had seminal infection with Enterococcus, two each had penile warts and an undescended testicle, and one each had Y chromosomal translocation.

Three men were excluded because of maturation arrest and congenital epididymal obstruction. The remaining 24 men had a mean age of 37 (range of 26 to 54), and 20 (83.3%) were evaluated for primary infertility.

All 24 men were taking low-dose finasteride for baldness, and treatment duration averaged 57.4 months. Reported doses ranged from 1.0 to 1.25 mg/d and averaged 1.04 mg/d.

None of the men had hormonal evaluations before and after discontinuation of finasteride. Nine men with pre-finasteride evaluations had mean values of 7.96 IU/L for FSH and 5.6 IU/L for LH. Post-finasteride values in eight men averaged 7.3 IU/L for FSH and 6.3 IU/L for LH.

The authors found that 14 of the 24 men had semen analyses before and after discontinuation of finasteride, and the time between measurements averaged 6.5 months. After stopping finasteride, the men's mean sperm concentration increased (13.2 to 42.25 M/mL, P=0.003), but sperm motility and morphology did not change significantly.

Sperm count increased significantly from 32.34 to 127.62 M/mL (P=0.002). Sperm count increased across the range of values prior to discontinuation of finasteride, including an 11.6-fold increase among nine men who were oligospermic (<15 M/mL) before they stopped finasteride.

"Low-dose finasteride does appear to exert a negative effect on fertility in some men," the authors said in their discussion of the findings. "When we discontinued finasteride treatment in our patients, we found a significant increase in sperm count ... which was more notable in men with severe oligospermia at initial assessment."

Case reports have suggested that sperm counts improve within 3 months after discontinuing finasteride, they added.

"However, because we do not know the mechanism of effect of finasteride, it is difficult to predict a timeline for improvement," they said.

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