When browsing through the hair loss forums in the past years, I always noticed that many people were wondering if finasteride has the potential to hurt muscle gains.
Many people like to stay in shape these days (myself included), so I guess that is the reason why this question is so popular for many.
Individuals who are into bodybuilding might also use testosterone so that they can benefit from supraphysiological levels. Or they might use compounds that have a strong affinity to the androgen receptor.
If you are sensitive to androgenetic alopecia (male pattern baldness), doing this could start or speed up your hair loss. The reason for this is that androgens and androgen receptors play a primary role in androgenetic alopecia.
Increased testosterone levels and androgen receptor activity will probably harm your hair follicles if you are susceptible to hair loss.
So if you are doing this, finasteride might be worthful to look at. That is of course if you care about your hair.
Answering the question
Let’s go back to the original question of this post though and see if we can answer the question.
Many people think that finasteride has an effect on muscle gains. After all, finasteride decreases DHT tremendously. DHT is more potent than testosterone. In fact, DHT binds way more strongly to the androgen receptor.
Taken the above, this leads us to think that finasteride does have an impact on muscle hypertrophy of skeletal muscle. It would almost have to affect our muscle gains. Right?
Well, not really.
First of all, DHT as a hormone works primarily in an autocrine/paracrine way. So it is mostly active in the tissue where it is synthesized.
Furthermore, we know that DHT synthesis happens out of testosterone through the enzyme 5-alfa-reductase. There are 3 types of these enzymes (1 , 2 and 3).
Now in skeletal muscle only type 3 is somewhat expressed while type 1 and 2 are virtually not.
Finasteride doesn’t have strong biological activity towards 5-alfa-reductase type 3. So it doesn’t have such an impact on the local synthesis of DHT in skeletal muscle.
But DHT that is available in the bloodstream will reach skeletal muscle and finasteride does massively reduce serum DHT.
In skeletal muscle, however there is a rich abundance of the enzyme 3alpha-hydroxysteroid reductase (3a-HSD). This enzyme quickly deactivates DHT.
(Man, do I wish that this enzyme would be present in hair follicles. Would be lovely if someone can find out how to do this!)
Testosterone is the main active androgen in muscle
So the little DHT that forms in skeletal muscle tissue and the DHT that is present in the blood will get quickly deactivated. It is likely that if there was a way to block 3a-HSD that it would result in DHT playing a bigger role in muscle hypertrophy.
So you can see how testosterone and not DHT is the active androgen in muscle.
A randomized clinical trial from 2012 also confirms this. The conclusion from the study:
Changes in fat-free mass in response to graded testosterone doses did not differ in men in whom DHT was suppressed by dutasteride from those treated with placebo, indicating that conversion of testosterone to DHT is not essential for mediating its anabolic effects on muscle.
Take note that dutasteride is even a stronger compound than finasteride is in suppressing DHT.
Even from the anecdotal reports that I have read, most of the people that use finasteride and are active in the gym don’t seem to be affected at all.
An example is “peapoddy” who is into bodybuilding as you can see here above. He uses finasteride and mentioned that finasteride didn’t hurt him in any way. As you can see he had pretty great results with finasteride in combination with minoxidil.
Now that’s not to say that there aren’t any anecdotal claims of finasteride affecting people their muscle growth. I have certainly seen people report that they felt that finasteride hurt their gains.
Perhaps finasteride can hinder muscle growth through indirect means.
For instance, finasteride could lower your mood or induce fatigue which would result in less activity in the gym. This will of course result in less muscle growth.
The evidence that we have is pretty straight forward and very convincing.
Finasteride shouldn’t have any impact on muscle gains directly. So this shouldn’t be of any concern at all.