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 . 
Interestingly, Trenavar and Trenbolone – also known as “Tren” – are so alike that cycling with this prohormone will actually lead to the stimulation of the naturally active trenbolone in the body, leading to greater vascularity, faster loss of fat as well as considerable boosts in size and strength. This is because Trenavar targets the 17b-Hydroxysteroid dehydrogenase type 1 (17b-HSD1) when it gets metabolized by the body. As soon as the compound of Trenavar gets hydrogenated inside the system, its conversion into Trenbolone takes place.