Testosterone enanthate ( USAN , BAN ) (brand names Delatestryl , Testostroval , Testro LA , Andro LA , Durathate , Everone , Testrin , Andropository ), or testosterone heptanoate , is an androgen and anabolic steroid and a testosterone ester .    Along with testosterone cypionate and testosterone propionate , it is one of the most widely used testosterone esters.  Testosterone enanthate was first introduced in 1952.  Administered via intramuscular injection , it is the most widely used form of testosterone in androgen replacement therapy . 
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.     
Most preparations containing testosterone or its salts, esters, or ethers are subject to control under the Federal Controlled Substances Act of 1970, as amended by the Anabolic Steroids Control Act of 1990 and 2004, as schedule III (C-III) drugs. 113 164 However, manufacturers of certain preparations containing androgenic anabolic steroid hormones (principally combinations that also include estrogens) have applied for and obtained for their products(s) an exemption from the record-keeping and other regulatory requirements of the Federal Controlled Substances Act. 121 165 Under provisions of the Act, specific products can be exempted from such control by the Attorney General, in consultation with the Secretary of Health and Human Services, if the product is determined not to possess any significant potential for abuse because of concentration, preparation, combination, and/or delivery system. Because regulatory requirements for a given preparation containing an androgenic anabolic steroid may be subject to change based on these provisions, the manufacturer should be contacted when specific clarification about a preparation’s status is required.