HCG is a peptide hormone manufactured by the embryo in the early stages of pregnancy and later by the placenta to help control a pregnant woman’s hormones (can anything really be said to control a pregnant woman’s hormones except ice-cream and chocolate?). Obviously, as you can guess from the name, it is a substance that stimulates the gonads (hence: gonadotropin). It does this by initiating gene transcription that is identical to that of Luetenizing Hormone, thereby causing the Leydig Cells to produce testosterone. Sounds great right? We can stimulate LH and FSH production with our Nolvadex, and then directly stimulate the Leydig Cells as well, to produce tons of testosterone by different routes! Well…it’s not all that simple.
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 .