Masteron is an injectable preparation containing the steroid drostanolone propionate. Drostanolone is a derivative of dihydrotestosterone, most specifically 2alpha-methyldihydrotestosterone. As a result, the structure of Masteron is that of a moderate anabolic/potent androgen which does not aromatize to estrogen. Water retention and gynecomastia therefore do not come into play with Masteron. Masteron may in fact exhibit anti-estrogenic activity in the body, competing with other substrates for binding to aromatase... -- more about MASTERON --