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.     
Follicle Stimulating Hormone (FSH) - In women FSH is often used as a gauge of ovarian reserve. In general, under 6 is excellent, 6-9 is good, 9-10 fair, 10-13 diminished reserve, 13+ very hard to stimulate. In PCOS testing, the LH:FSH ratio may be used in the diagnosis. The ratio is usually close to 1:1, but if the LH is higher, it is one possible indication of PCOS. Basic hormone testing for males often only includes testosterone and FSH. However, in cases such as Klinefelters Syndrome doctors will usually look at both FSH and LH levels. In males FSH stimulates the Sertoli cells in the testes to produce androgen-binding proteins, testosterone, and a protein called inhibin. Inhibin, in turn, travels in the blood back to the pituitary gland whre it creates a "negative feedback loop" that decreases the output of FSH. Since FSH stimulates testosterone production, and testosterone can be converted to DHT and estradiol, an increase of any or all three can also create a "feedback loop" that decreases FSH secretion.