Do 5-alpha reductase inhibitors affect muscle strength enhanced by exogenous testosterone?

According to a trial, treatment with dutasteride (Avodart), a 5-alpha reductase inhibitor, doesn’t affect fat-free mass in healthy men who use testosterone.
A study connected with this issue was performed. While fat-free mass was increased by 0,6-7,1 kg during 20 weeks in males who administered dutasteride and Testosterone Enanthate, fat-free mass was enhanced by 0,8-8,1 kg in those who applied placebo and testosterone. As for muscle power, sexual functions and volume of prostate, they didn’t differ in males of these two groups.
5-alpha reductase inhibitors are applied clinically to cure benign prostatic hyperplasia (BPH) and androgenic alopecia. These are disorders which commonly appear in middle-aged and old males.
DHT represents the chief metabolite of testosterone. But the role of DHT in human development is not studied well. It is supposed that DHT has important role in development of prostate and phallus.
Middle-aged and old men with reduced testosterone levels who administer testosterone medications have risks linked with reduced muscle size and sexual troubles.
Specialists also put efforts to develop nonsteroidal selective androgen receptor modulators (SARMs). It is claimed that SARMs and 5-alpha reductase inhibitors are safe because DHT is probably not necessary for effects on fat-free mass, strength 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 set 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 enrolled healthy males that were 18- 50 years old and had normal testosterone levels. They were given Testosterone Enanthate and dutasteride or placebo. Doses of Testosterone Enanthate varied from 50 to 600 mg weekly.
Since 5 ?-reductase inhibitors enhance testosterone levels, all men 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 significantly in males of these two groups. Muscle strength that was also enhanced due to administration of testosterone didn’t differ between the two groups as well. Sexual functions, prostate volume, sebum production, hemoglobin, acne, hematocrit didn’t differ substantially between those who administered placebo and dutasteride.
The specialists claim that effectiveness of 5?-reductase inhibitors can be limited in men that have normal or high levels of testosterone. That’s why it is important to measure 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 have to know that if they have high testosterone levels or introduce exogenous testosterone in their bodies, 5?-reductase inhibitors will not cause shrunken prostate.