So, we see that steroid hormones control many vital functions in your body. Of course, we wouldn't have these or any steroids if we did not have cholesterol. It could be said that the most important steroid molecule in your body is cholesterol , because cholesterol is the parent compound from which steroids are derived. It is basically the precursor for steroid hormones and other steroids. We see by looking at the structure of cholesterol that it is a steroid, because it has the four rings of carbon atoms. Attached to the rings we see a hydrocarbon tail and a hydroxyl group . Cholesterol is a 27-carbon steroid and has a molecular formula of C27H45OH.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine .