It’s the perfect drug for 40 million men in America who are going bald. Take it once a day to keep the hair on your head and shrink the prostate, which also commonly bothers men as they age. It’s a pill that has been used by at least 2 million reproductive age men over the last decade. But is it too good to be true?
The Best Hair Pill Yet
This magic pill is finasteride (trade names; Propecia, Proscar, Avodart). It represents a class of drug called the 5-alpha reductase inhibitors. These pills act as enzyme blockers: they prevent the male hormone testosterone from converting to its metabolite dihydrotestosterone (DHT). Although testosterone is responsible for a lot of our “male” features, DHT is more potent than testosterone for scalp hair and our internal reproductive organs (prostate, seminal vesicle). These drugs work by lowering DHT production and protect the gloriously youthful hair on our heads and the enviable ability to write your name in the snow while urinating.
And these drugs work well. More effective than topical or “rub in” medications, finasteride is great for what’s called “male pattern” hair loss which is due to a receding hairline or balding on the top of the head. In essence, it slows the growth phase of hair in these areas. However, it doesn’t treat hair loss on the sides or temple area.
Finasteride, Sex and Male Fertility
Although it may keep you looking like Clark Kent, many male infertility specialists, including myself, have concerns about finasteride. First, there is a 10% chance of sexual side effects that include erectile and ejaculatory dysfunction and lowering of sex drive. These issues can be subtle while on the pill but become very obvious when men stop it; many of my patients have noted a sexual “curtain being lifted” or “coming alive” after discontinuing the pill.
Second, there is an even more profound concern about finasteride among specialists: male infertility. Before it received FDA approval, the drug trials showed that it lowered ejaculate volume but did not change sperm count or motility on semen analysis testing (actual human fertility studies are not routinely required by the FDA). Now that it has been on the market for 10 years, though, impressive declines in semen quality have been observed and published with finasteride by many of us. This effect is not subtle either, as patients with complete sterility (azoospermia) have had recovery of their sperm counts after stopping finasteride!
There are several clues that this effect on fertility was possible. The rabbit studies done for FDA approval of the drug actually showed this effect. At 3 months, there was no effect on rabbit fertility. But, when followed longer, rabbits showed significant decreases in natural fertility. In addition, while I was writing a recent reproductive physiology chapter for Campbell-Walsh Urology, our leading urology textbook, I researched at what levels the 5-alpha reductase enzyme is found in the human testis and epididymis. Lo and behold, there are gobs of this enzyme in these important organs for sperm production and maturation, implying that the blocking agent finasteride would have an effect. So now what do we do?
At this point, controlled clinical trials are needed to prove this effect on fertility. For the time being, current thinking is that finasteride may not dramatically change sperm production in healthy men, but can impair semen quality in infertile men. Typically, the effects of medications on male infertility are reversible. So, to be proactive men should consider stopping the pill at least 6 months prior to trying to conceive. And, have confidence that she loves you just as much for other reasons. As Telly Savalas once said: “We’re all born bald, baby!”