Anabolic androgenic steroids (AAS) were initially created for therapeutic purposes, and synthetic derivatives of the male hormone testosterone. Due its great anabolic effects, these drugs are being used on a large scale, for the improvement of sports performance. In this present study, we aim to show the history of it’ use, present their mechanisms of action, more particularly its use correlate with improved body composition, muscle mass, aerobic capacity and verify their possible side effects, analyzing their use therapeutic and indiscriminate, through direct scientific research with the sports. Sources were reviewed scientific the following search engines: PUBMED, LILACS and SCIELO. The results showed that in presence of a suitable AAS and diet can contribute to increases in body weight, particularly lean body mass and muscle strength gains achieved by high intensity exercise, these effects can be further potentiated, the use of supraphysiological doses, but in the aspect of aerobic power, there are not scientific evidence to support their improvement. Regarding side effects, the use of AAS, is related to several complications in the liver, cardiovascular system, reproductive system and psychological characteristics, always assigned by the non-therapeutic and abuse of AAS. Thus we conclude that the use of AAS, are directly linked to gains muscle mass, strength, as well several side effects, always assigned to abusive and indiscriminate doses, it is noteworthy that the scientific literature, still has a certain lack of studies, mainly randomized, controlled, with supraphysiological doses in human, so many effects are still unknown.
Mesterolone is rumored to have a stimulatory effect on testicular function. This is not true. This rumor is likely attributed to the fact that, when used at therapeutic doses, this steroid will not suppress gonadotropin release (gonadotropins are released by the brain to signal the production of testosterone and sperm). As gonadotropin levels are not suppressed as a result of moderate doses of Proviron®, testicular function will remain at normal levels. While clinical trials have yet to confirm this, some clinicians argue that this drug may stimulate the production of sperm (not testosterone). While it has been shown that Proviron® use at 150mg/day will not significantly decrease testicular function (sperm production/testosterone production), extreme doses of this drug (250mg/day+) will suppress testicular function (which is likely to include the production of sperm).
The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression".   Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.  The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.  Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.