DHT blockers namely, Finasteride and  Dutasteride are used in the treatment of Androgentic alopecia or Male Pattern baldness. In fact, DHT blockers are the only medicine that can reverse the miniaturisation effects of genes occurring at the level of your hair follicle and convert the vellus (small and fine baby hair) back into terminal hair (long and thick hair of scalp).

In this article, we have provide you with scientific data regarding effect of DHT blockers on quality of sperms and fertility.

 

What is DHT?

DHT stands Dihydro-testosterone. In males, 4-8% of testosterone is converted to DHT by enzyme 5 alpha reductase. DHT has role in development of male reproductive organs, however, its role in adults is limited to hair and prostate only. This is the reason increase DHT levels are associated with Androgenetic alopecia and Begnin Prostate Hyperplasia.

 

Finasteride versus Dutasteride

Finateride has been approved by FDA for use in AGA in 1997.

Finasteride and Dutasteride, both work by inhibiting 5 alpha reductase enzyme, thus, reducing conversion of testosterone to DHT. However, there are differences in the mechanism of action and its impact of sperms as tabulated below:

 

Finasteride 5 mg (high dose) Dutasteride 0.5 mg
Inhibits type 2 alpha reductase enzyme only Inhibits type 1 and type 2 alpha reductase enzyme
Reduces level of DHT by 70% approximately Reduces level of DHT by 90% approximately
DHT level recover after stopping medicine in 8 weeks DHT level recover after stopping medicine in 12 weeks
Semen volume and count decreased but was not statistically significant. Semen volume and count decreased but was not statistically significant.
Sperm motility decreased in 10%, which persisted in 9% at follow up of 1 year.

However, this change was small, according to author.

Sperm motility decreased in 10%, which persisted in 6% at follow up of 1 year. However, this change was small, according to author.
Sperm morphology was normal. Sperm morphology was normal

Reference : This study. Point to be noted here is that in the above study, 5 mg of Finasteride was used, however, we use much less dose of 1 mg in male pattern hair loss. Therefore, the above changes might be 5 times less.

 

Can Finasteride affect the sperm and result in infertility?

There is no definite answer to this question. Majority of males who have decrease in sperm count after taking finasteride for one year, recover the sperm counts after 3 months of discontinuation. However, there are case reports of males who might have prolonged changes in sperm after taking Finasteride, especially, those who are prone to sub-fertility and have oligospermia in the beginning of therapy.

A case report of  48-year-old man on 1 mg  finasteride for one year was unable to bear children. His DNA fragmentation index (DFI) in semen was decreased by 30 %. After 3 months of stopping finasteride, it the effect on sperms reduced and his DFI improved to 21 % after 3 month and 16.5% after 6 month of stopping Finesteride. To date, there is still no documented full-term pregnancy or live birth. Interestingly, his semen analysis was normal.

On the other hand, in this case report, 2 male with oligospermia due to finasteride 1mg for 1 year, showed significant improvement in sperm parameters after 6 months of stopping the treatment.

In study done in 2013 in infertility clinic, 27 men on 1 mg finasteride daily for average 57.4 months, saw increase in average 11.6-fold increase in sperm counts after finasteride discontinuation. Of the men with severe oligospermia (<5 M/mL), 57% had counts increase to >15 M/mL after finasteride cessation. There was no change in hormone parameters, sperm motility, or sperm morphology. Authors of study concluded that Finasteride, even at low doses, may cause reduced sperm counts in some men. Finasteride should be discontinued in sub-fertile men with oligospermia, and used with caution in men who desire fertility.

A recent study done in 2021 showed that the use of finasteride may affect Ca2+ signalling in human sperm through an interaction with the PGE1-binding site, but to which extend it alters the chances of a successful fertilization needs further investigation.

CONCLUSION: Finasteride does not affect fertility in majority, however, cautious use is recommended in patients prone to oligospermia.

 

Are there studies that report persistent sexual side effects of Finasteride?

Yes, there are studies that show men who developed persistent sexual side effects (≥3 months) despite the discontinuation of finasteride, the sexual dysfunction continued for many months or years.

US Food and Drug Administration also mentions that finasteride, 1 mg, for androgenic alopecia has been associated with persistent sexual and nonsexual adverse effects.

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