Masteron is a highly androgenic injectable steroid that is derived from DHT (dihydrotestosterone). DHT does not aromatize to estrogen (and in fact may combat estrogenic sides), and as a result, there was no noted water retention during administration nor gynocomastia. Masteron is almost exclusively used during the last 4-5 weeks before a bodybuilding show at a dose of 100-mg every second day. Additionally, according to available literature, Masteron is not much of a mass drug, and it's always used for cutting, from what I've seen reported. Masteron has a receptor binding ability above that of testosterone, due to it's being DHT-derived, which should impart lypolytic (fat-burning) effects above that of testosterone, and also give it a nice strength building component.
Masteron can bind to Sex-Hormone-Binding-Globulin, which prevents AAS from merging with their receptors. Masteron can stop this from happening. This may mean that it enhances cycles, by letting other steroids work more effectively. Proviron, which is often called "oral masteron" (*correctly) does this very well also.
Usually, Masteron would be stacked with Testosterone Propionate and possibly Trenbolone Acetate, which would be administered all at once, every second or third day in the same injection.
