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.     
Endogenous androgens are responsible for the normal growth and development of the male sex organs and for maintenance of secondary sex characteristics. These effects include the growth and maturation of prostate , seminal vesicles , penis , and scrotum ; the development of male hair distribution, such as beard , pubic, chest and axillary hair, laryngeal enlargement, vocal cord thickening, alterations in body musculature, and fat distribution. Drugs in this class also cause retention of nitrogen , sodium, potassium , phosphorus , and decreased urinary excretion of calcium. Androgens have been reported to increase protein anabolism and decrease protein catabolism . Nitrogen balance is improved only when there is sufficient intake of calories and protein. Androgens are responsible for the growth spurt of adolescence and for the eventual termination of linear growth centers. In children, exogenous androgens accelerate linear growth rates, but may cause a disproportionate advancement in bone maturation. Use over long periods may result in fusion of the epiphyseal growth centers and termination of growth process. Androgens have been reported to stimulate the production of red blood cells by enhancing the production of erythropoietic stimulating factor.
Test HD is the first hardcore testosterone booster to include a clinical-strength dose of shilajit, a rare organo-mineral compound obtained from steep rocks of different formations found in the Himalayas and other high mountains. Shilajit in its natural state has no chemical definition. In order to yield a consistent and efficacious form of shilajit, the shilajit is obtained from carefully selected rocks and is put through a patented technology where it is purified and standardized. This form of shilajit is now assured of optimal levels of bioactive components such as fulvic acid and dibenzo-pyrones, and is known as the patented PrimaVie.