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.     
While the adrenal glands still help out with testosterone and progesterone production in later years, the amount supplied is extremely small. The biggest issue that we see is an end to normal estrogen levels when the body converts excess testosterone into estradiol. This causes an imbalance that leads to a condition called estrogen dominance – where estrogen is now unopposed by progesterone and testosterone because their levels have declined. Estrogen dominance leads to weight gain, which further increases testosterone to estrogen conversion.