5-alpha reductase inhibitors, testosterone use and fat-free mass

According to a trial, treatment with dutasteride (Avodart), a 5-alpha reductase inhibitor, doesn’t influence negatively on fat-free mass in healthy men who take testosterone.
A study related to this issue was conducted. While fat-free mass was enhanced by 0,6-7,1 kg during 20 weeks in men that administered dutasteride and Testosterone Enanthate, fat-free mass was increased 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 two groups.
5-alpha reductase inhibitors are applied clinically to treat benign prostatic hyperplasia (BPH) and androgenic alopecia. These are disorders which commonly appear in middle-aged and old men.
DHT represents the chief metabolite of testosterone. But the role of DHT in human development is not clearly understood. It is suggested that DHT has relevant role in development of prostate and phallus.
Middle-aged and elder males with low testosterone levels that use testosterone preparations have risks connected with low muscle mass and sexual disorders.
Nonsteroidal selective androgen receptor modulators (SARMs) are also currently studied and developed. It is affirmed 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 some other factors.
Shalender Bhasin and his colleagues at the Boston University have performed a clinical trial in order to define whether 5?-reduction to DHT is needed in order to mediate androgen’s effects on fat-free mass. Furthermore, the scientist evaluated role of 5?-reduction on sexual functions, hematocrit and levels of lipid.
The study conducted by Bhasin and his colleagues implicated healthy men that were 18- 50 years old and had normal testosterone levels. They administered Testosterone Enanthate and dutasteride or placebo. Doses of Testosterone Enanthate varied 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 manifested that fat-free mass was enhanced due to application of testosterone. It didn’t differ significantly in men of these 2 groups. Muscle power which was also increased due to administration of testosterone didn’t differ between the two groups too. Sexual activity, volume of prostate, sebum production, hemoglobin, acne, hematocrit didn’t differ essentially between those who used placebo and dutasteride.
The specialists affirm that effectiveness of 5?-reductase inhibitors may be limited in men that have normal or enhanced levels of testosterone. That’s why it is necessary to check testosterone levels in order to determine how bodies will respond to 5 ?-reductase inhibitors.
So, the research has manifested that muscle mass is not affected by 5?-reductase inhibitors.  Males should know that if they have high testosterone levels or introduce exogenous testosterone in their bodies, 5?-reductase inhibitors will not cause shrunken prostate.