The great popularity of this injectable steroid in bodybuilder circles is due to the extraordinary characteristics of its included substance. Drostanolone propionate is a synthetic derivative of dihydrotestosterone. This causes the Drostanolone not to aromatize in any dosage and thus, it cannot be converted into estrogens. Since Mastabol is a predominantly androgenic steroid, the athlete can increase his androgen level without also risking an increase in his estrogen level.