Thursday, May 19, 2011

Finasteride side effects: a real concern? by Jerry Brainum

Finasteride is sold as Proscar and Propecia, and also is sold in  generic form.As Proscar, finasteride was approved for sale by the FDA in 1992 for the treatment of benign prostatic enlargement, or an enlarged prostate gland. This was based on the fact that the primary cause of enlarged prostate glands is due to stimulation of the gland by dihydrotestosterone (DHT). DHT, in turn, is a metabolite of testosterone. In fact, in most tissues other than muscle, DHT is far more potent then testosterone.While DHT is the arbiter of male sexual characteristics, including sexual organ development, male body hair configuration, and so on, it is also responsible for such undesirable effects as male pattern baldness, prostate enlargement, and acne onset. While Proscar comes in a 5 milligram dose, studies showed that large a dose wasn't required to help prevent and treat male pattern baldess (MPB). As such, the FDA appoved the sale of a 1 milligram dose of finasteride specifically to treat MPB in 1997. That drug was called "Propecia."
    Bodybuilders have used either Proscar or Propecia in conjunction with anabolic steroid stacks because many of the available steroids are based on a DHT structure, and are therefore capable of promoting MPB. One reason why not all steroid users lose their hair is because MPB, while stimulated by DHT, is actually directly caused by certain genes. The genes make the hair follicles more sensitive to the effects of DHT. Recently, however, reports have emerged of serious sexual problems related to the use of Propecia. These effects include impotence and loss of libido, or sex drive, as well as low ejaculate, loss of sexual sensation, and so on. According to the existing medical literature, only 2% of users of Propecia suffer serious sexual side effects, and most regress upon discontinuance of the drug. However, the most recent reports have found that in some cases, the sexual side effects, including impotence, are permanent. I've seen recent blogs that warn that using finasteride will completely destroy your sex life permanently.
     There is no doubt that some users of finasteride will experience sexual side effects from the drug. But to claim that it will happen to every man who uses it just isn't true. These stories say that the sexual effects even persist long after a person stops using finasteride. I have a problem with this for several reasons. First, DHT is not, contrary to blog statements, responsible for libido or sex drive. Testosterone is the primary hormone responsible for sex drive in both sexes, not DHT. Another aspect of the controversy that I find curious is that those who claim that finasteride is causing these side effects say that the drug completely blocks DHT in the body. In fact, finasteride works by blocking type-2, 5-alpha reductase enzyme, which is active in hair follicles and the prostate gland. It has no effect on the other type of 5-alpha reductase enzyme, namely type-1. A newer drug, dutasteride, or Avodart, does affect both enzymes, and is considerably more potent in this regard compared to finasteride. In addition, finasteride does not completely block DHT. It blocks 67% of serum DHT. This means that you still have 33% of normal DHT being produced in your body even when you use finasteride. But the question remains: why do certain men experience serious sexual side effects when using finasteride, while others use it for years with no apparent side effects whatsoever?
     My guess is that in those who experience the side effects, finasteride is somehow creating an androgen insensitivity syndrome. This has to do with a type of genetic pattern that is beyond the scope of this article.But if you don't have this particular gene pattern, you won't experience the sexual side effects, or the effects will be much milder, certainly no impotence or loss of libido. As an alternative explanation, perhaps some men are more sensitive to the neurosteroid characteristics of DHT. A "neurosteroid," means it has activity in the brain. DHT is known to affect memory, sleep onset, anxiety, and other mental effects. Recently, finasteride has been shown to cause depression in some men. This would directly relate to the neurosteroid effects of DHT. It also would explain the loss of libido and perhaps even the impotence experienced by a minority of users of the drug. From a sports perspective, the neurosteroid properties of DHT are thought to increase aggressiveness, and some say this makes for more intense training in the gym, or when participating in sports. I also wonder about the power of suggestion in this instance. If you firmly believe that a drug will cause side effects, it often does. It's sort of a placebo effect. This is the reason why most doctors won't tell male patients that anti-depressant drugs have a 5% incidence of causing impotence. History shows that when such effects are mentioned, some men who use the drug will quickly report the onset of impotence.
     My point in writing all this is that those who say that using finasteride will cause serious sexual side effects in all users of the drug are just spouting nonsense. It's comparable to saying that all those who use anabolic steroid drugs will show signs of "roid rage." Some will, many won't. Recently, some animal studies have shown that  DHT can be directly produced in muscle after exercise, including endurance training. Can this form of DHT affect tissues other than muscle? Only further studies will answer that question.

©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.

Have you been ripped off by supplement makers whose products don’t work as advertised? Want to know the truth about them? Check out Jerry Brainum's book Natural Anabolics, available at


The Applied Ergogenics blog is a collection of articles written and published by Jerry Brainum over the past 20 years. These articles have appeared in Muscle and Fitness, Ironman, and other magazines. Many of the posts on the blog are original articles, having appeared here for the first time. For Jerry’s most recent articles, which are far more in depth than anything that appears on this blog site, please subscribe to his Applied Metabolics Newsletter, at This newsletter, which is more correctly referred to as a monthly e-book, since its average length is 35 to 40 pages, contains the latest findings about nutrition, exercise science, fat-loss, anti-aging, ergogenic aids, food supplements, and other topics. For 33 cents a day you get the benefit of Jerry’s 53 years of writing and intense study of all matters pertaining to fitness,health, bodybuilding, and disease prevention.


See Jerry's book at


Want more evidence-based information on exercise science, nutrition and food supplements, ergogenic aids, and anti-aging research? Check out Applied Metabolics Newsletter at