Testosterone is a hormone that is produced in large amounts by males (and a little bit in females), in the testes and adrenal glands. High testosterone levels are associated with sexual performance, reproductive function, muscle mass, hair growth, aggressive, competitive behaviors, and other such manly things. Testosterone levels tend to peak at the age of 40, and slowly decline from there. Luckily, there are many things you can do to increase testosterone, so if you feel like your T levels could use a boost, you've come to the right place.
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.     
Ok so what’s so cool about this guy? It’s has clinical strength doses of shilajit which is retreived from very special rocks in the Himalaya mountains. They take it through a patented purification process that produces higher levels of of flvic acid and dibenzo-pyrones known as PrimaVie. These bioactive components, along with a powerful dose of boron make it super effective. The boron increases the free testosterone and decreases estradiol within 7 days. This free T is super important in building the lean muscle. You also have the other main ingredients: stinging nettle root, tribulus and velvet bean that you find in other competitive , the decision is really yours as to what extent you want to go with this. You can read more reviews here on amazon about what other customers say about TEST HD results.