Dutasteride doesn’t affect muscle mass in men that introduce exogenous testosterone into bodies

According to a trial, the 5-alpha reductase inhibitor dutasteride (Avodart) doesn’t affect muscle mass in healthy men that use testosterone.
A study connected with this issue was conducted. While fat-free mass was enhanced by 0,6-7,1 kg during 20 weeks in men that used dutasteride and Testosterone Enanthate, fat-free mass was enhanced by 0,8-8,1 kg in those who used placebo and testosterone. As for muscle power, sexual functions and volume of prostate, they didn’t differ in men of these 2 groups.
5-alpha reductase inhibitors are applied clinically for treatment of benign prostatic hyperplasia (BPH) and androgenic alopecia. These are dysfunctions which usually affect middle-aged and old men.
DHT represents the chief metabolite of testosterone. But the role of this metabolite in human development is not clearly understood. It is suggested that DHT has important role in development of prostate and phallus.
Middle-aged and old men with reduced testosterone levels that take testosterone medicines have risks related to reduced muscle mass and sexual problems.
Specialists also put efforts to develop nonsteroidal selective androgen receptor modulators (SARMs). It is confirmed that SARMs and 5-alpha reductase inhibitors are safe because DHT is probably not necessary for effects on fat-free mass, strength and sexual life. It is also doubted whether DHT plays any role for androgen’s effects on hematocrit, hemoglobin, lipids and certain other factors.
Shalender Bhasin and his colleagues at the Boston University have conducted a clinical trial in order to see whether 5?-reduction to DHT is needed in order to mediate androgen’s effects on muscle mass. Furthermore, the specialists evaluated role of 5?-reduction on sexual activity, hematocrit and levels of lipid.
The study conducted by Bhasin and his colleagues enrolled healthy men that were 18- 50 years old and had normal testosterone levels. They used Testosterone Enanthate and dutasteride or placebo. Dosages of Testosterone Enanthate varied from 50 to 600 mg weekly.
Since 5 ?-reductase inhibitors increase testosterone levels, all males were given also gonadotropin-releasing hormone agonist in order to block natural testosterone.
The results of the study showed that fat-free mass was increased due to application of testosterone. It didn’t differ substantially in males of these two groups. Muscle strength that was also increased due to testosterone use didn’t differ between the two groups as well. Sexual activity, volume of prostate, sebum production, hemoglobin, acne, hematocrit didn’t differ essentially between those who used placebo and dutasteride.
The specialists note that effectiveness of 5?-reductase inhibitors may be limited in males that have normal or high levels of testosterone. That’s why it is necessary to measure levels of testosterone in order to set how bodies will respond to 5 ?-reductase inhibitors.
So, the study has demonstrated that muscle mass is not affected by 5?-reductase inhibitors.  Men should know that if they have high levels of testosterone or introduce exogenous testosterone in their bodies, 5?-reductase inhibitors will not lead to shrinkage of prostate.