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.     
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Treatment of hypogonadal men with Sustanon 250 results in a clinically significant rise of plasma concentrations of testosterone, dihydrotestosterone, estradiol and androstenedione, as well as decrease of SHBG (Sex hormone binding globulin). Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are restored to the normal range. In hypogonadal men, treatment with Sustanon 250 results in an improvement of testosterone deficiency symptoms. Moreover, treatment increases bone mineral density and lean body mass, and decreases body fat mass. Treatment also improves sexual function, including libido and erectile function. Treatment decreases serum LDL-C, HDL-C and triglycerides and increases haemoglobin and haematocrit, which may lead to polycythaemia. No clinically relevant changes in liver enzymes and PSA have been reported. Testosterone also produces systemic effects, such as increasing the retention of sodium, potassium and chloride leading to an increase in water retention. Treatment may result in an increase in prostate size, and worsening of lower urinary tract symptoms, but no adverse effects on prostate symptoms have been observed. In hypogonadal diabeteic patients, improvement of insulinsensitivity and/or reduction in blood glucose have been reported with the use of androgens. In boys with constitutional delay of growth and puberty, treatment with Sustanon 250 accelerates growth and induces development of secondary sex characteristics. In female-to-male transsexuals, treatment with Sustanon 250 induces masculinisation.