MASTERON® (Drostanolone Propionate) is an injectable anabolic steroid derived from dihydrotestosterone (DHT). It is highly favored for its ability to produce solid increases in lean muscle mass with reductions in body fat level. 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 this steroid 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. This would reduce the conversion rate of other steroids, Masteron acting in the same way as the oral steroid Proviron. Since the propionate ester is used with this compound, injections need to be repeated at least every 3 or 4 days in order to maintain a consistent level of hormone in the blood.