Dutasteride doesn’t affect on muscle mass and power that are increased by testosterone use

According to a trial, the 5-alpha reductase inhibitor dutasteride (Avodart) doesn’t influence negatively on fat-free mass in healthy men that administer testosterone.
A research connected with this issue was conducted. While fat-free mass was increased by 0,6-7,1 kg during 20 weeks in men that were given dutasteride and Testosterone Enanthate, fat-free mass was enhanced by 0,8-8,1 kg in those that took placebo and testosterone. As for muscle strength, sexual functions and volume of prostate, they didn’t differ in males of these 2 groups.
5-alpha reductase inhibitors are applied clinically to treat benign prostatic hyperplasia (BPH) and androgenic alopecia. These are diseases that commonly appear in middle-aged and old men.
DHT represents the main metabolite of testosterone. But the role of this metabolite in human development is not clearly understood. It is supposed that DHT has relevant role in development of prostate and phallus.
Middle-aged and elder men with reduced testosterone levels that administer testosterone medications have risks related to decreased muscle mass and sexual troubles.
Scientists also study and develop nonsteroidal selective androgen receptor modulators (SARMs). It is affirmed that SARMs and 5-alpha reductase inhibitors are safe because DHT is supposedly not necessary for effects on muscle mass, strength and sexual activity. It is also doubted whether DHT has 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 experts evaluated role of 5?-reduction on sexual functions, hematocrit and levels of lipid.
The study conducted by Bhasin and his colleagues enrolled healthy men who were 18- 50 years old and had normal levels of testosterone. They applied Testosterone Enanthate and dutasteride or placebo. Dosages of Testosterone Enanthate ranged from 50 to 600 mg weekly.
Since 5 ?-reductase inhibitors increase testosterone levels, all men were given also gonadotropin-releasing hormone agonist in order to block natural testosterone.
The results of the study displayed that fat-free mass was enhanced due to administration of testosterone. It didn’t differ essentially in men of these two groups. Muscle strength that was also increased due to administration of testosterone didn’t differ between the two groups too. Sexual activity, prostate volume, sebum production, hemoglobin, acne, hematocrit didn’t differ essentially between those who used placebo and dutasteride.
The scientists conclude that effectiveness of 5?-reductase inhibitors may be limited in men that have normal or increased levels of testosterone. That’s why it is important to measure testosterone levels in order to set how bodies will respond to 5 ?-reductase inhibitors.
So, the research has demonstrated that muscle mass is not affected by 5?-reductase inhibitors.  Males have to know that if they have high levels of testosterone or introduce exogenous testosterone in their bodies, 5?-reductase inhibitors will not cause shrinkage of prostate.