It's a steroid...
"Superdrol (methasteron) is definitely not a prohormone: it is a very active form of a designer supplement. Superdrol gets its name from the fact that it is a super-saturated, or 2-reduced, form of Anadrol. Anadrol has a =C-OH at the 2nd position, and if this is totally saturated (reduced) with hydrogen, it gives -CH3. Another way to describe it is that it is a 2a-17a-dimethyl of drostanolone (Masteron). Masteron has a single methyl group at the 2nd position. Superdrol is a modification of this structure by adding another methyl group at the 17th position, like M1T or M-Dien. However you may wish to look at it, it is by this simple-looking transformation that Superdrol comes to occupy the sweet spot between the chemical natures of Anadrol and Masteron. "