As a non-aromatizing androgen, dihydrotestosterone is extremely potent. Aromatization refers to the conversion of testosterone or anabolic steroids into estrogen. High estrogenic activity causes bloating, acne, water retention and oily skin. As dihydrotestosterone does not aromatize even at high dosages, users do not face the aforementioned side-effects. Lack of water retention also has a hardening effect on muscle tissue, in bodybuilders. Being a powerful androgen, dihydrotestosterone is also responsible for a shift in the estrogen-testosterone ratio in the body. Due to its predominant androgenic component, the steroid has a stimulating effect on the adreno-pituitary functions, and causes neurological excitation in the ‘sexual orientation areas of the brain’. This in turn, spikes sex drive in males.
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 . 
The immediate effects of AAS in the brain are mediated by their binding to androgen (male sex hormone) and estrogen (female sex hormone) receptors on the surface of a cell. This AAS–receptor complex can then shuttle into the cell nucleus to influence patterns of gene expression. Because of this, the acute effects of AAS in the brain are substantially different from those of other drugs of abuse. The most important difference is that AAS are not euphorigenic, meaning they do not trigger rapid increases in the neurotransmitter dopamine , which is responsible for the “high” that often drives substance abuse behaviors. However, long-term use of AAS can eventually have an impact on some of the same brain pathways and chemicals—such as dopamine, serotonin, and opioid systems—that are affected by other drugs of abuse. Considering the combined effect of their complex direct and indirect actions, it is not surprising that AAS can affect mood and behavior in significant ways.