Does dutasteride affect muscle mass increased due to testosterone use?

According to a trial, the 5-alpha reductase inhibitor dutasteride (Avodart) doesn’t affect muscle mass in healthy men who apply testosterone.
A study connected with this issue was conducted. While fat-free mass was increased by 0,6-7,1 kg during 20 weeks in males who applied dutasteride and Testosterone Enanthate, fat-free mass was increased by 0,8-8,1 kg in those that used placebo and testosterone. As for muscle power, sexual functions and volume of prostate, they didn’t differ in males of these 2 groups.
5-alpha reductase inhibitors are utilized clinically to treat benign prostatic hyperplasia (BPH) and androgenic alopecia. These are disorders that commonly occur in middle-aged and elderly males.
DHT represents the main metabolite of testosterone. But the function of DHT in human development is not is not understood. It is suggested that DHT plays vital role in development of prostate and phallus.
Middle-aged and old men with reduced testosterone levels that administer testosterone medications have risks linked with decreased muscle mass and sexual troubles.
Nonsteroidal selective androgen receptor modulators (SARMs) are also currently studied and developed. It is claimed that SARMs and 5-alpha reductase inhibitors are safe because DHT is probably not necessary for effects on fat-free mass, energy and sexual activity. 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 conducted a clinical trial in order to define whether 5?-reduction to DHT is required in order to mediate androgen’s effects on fat-free 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 involved healthy males who were 18- 50 years old and had normal levels of testosterone. They used Testosterone Enanthate and dutasteride or placebo. Quantities of Testosterone Enanthate ranged from 50 to 600 mg per week.
Since 5 ?-reductase inhibitors enhance levels of testosterone, all men were given also gonadotropin-releasing hormone agonist in order to block natural testosterone.
The results of the research showed that fat-free mass was increased due to administration of testosterone. It didn’t differ essentially in men of these two groups. Muscle power which was also enhanced due to application of testosterone didn’t differ between the two groups too. Sexual activity, prostate volume, sebum production, hemoglobin, acne, hematocrit didn’t differ substantially between those who were given placebo and dutasteride.
The specialists affirm that effectiveness of 5?-reductase inhibitors may be limited in males who have normal or high testosterone levels. That’s why it is necessary to measure testosterone levels in order to determine how bodies will respond to 5 ?-reductase inhibitors.
So, the study has manifested that muscle mass is not affected by 5?-reductase inhibitors.  Males have to know that if they have increased levels of testosterone or introduce exogenous testosterone in their bodies, 5?-reductase inhibitors will not lead to shrinkage of prostate.