Drostanolone Propionate
Also known as Masteron, Drostanolone or Dromostanolone
There are two different variants of Masteron:
Drostanolone Propionate
Drostanolone Enanthate 
Biochemistry of Masteron / Drostanolone
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.
his 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.
Drostanolone is injected into the body as an ester (bonded to either Propionate or Enanthate). Enzymes cleave off the ester from the Masteron molecule – which takes varying amount of time depending on which ester was used. This process causes the gradual release rate and extended half-life of the steroid. Drostanolone Propionate has a half-life of 2.5 days, while Drostanolone Enanthate has a half-life of 10 days.
Intended use of Drostanolone / Masteron
Masteron was initially marketed as a treatment of female breast cancer. Because it pronounced male characteristics in women and because more effective breast cancer treatments were invented, Drostanolone was gradually phased out.