Masteron is a modified form of Dihydrotestosterone, with a methyl group at the 2nd carbon (carbon alpha) atom. This modification is responsible for the anabolic strength increase. This methyl group makes it harder for the enzyme 3-hydroxysteroid dehydrogenase to metabolize Masteron.
This enzyme is abundantly present in muscle tissue, and is responsible for degrading any DHT into two inactive metabolites: 3-Alpha Androstanediol and 3-Beta Androstanediol. Because of this enzyme DHT is not anabolic in muscle tissue at all. It is believed that if the enzyme 3-hydroxysteroid dehydrogenase was neutralized, DHT would actually be a very powerful anabolic steroid. Drostanolone’s methyl group addition makes it imune to this enzyme.