For both men and women, an alternative to testosterone replacement is low-dose clomifene treatment, which can stimulate the body to naturally increase hormone levels while avoiding infertility and other side effects that can result from direct hormone replacement therapy.  This therapy has only been shown helpful for men with secondary hypogonadism. Recent studies have shown it can be safe and effective monotherapy for up to 2 years in patients with intact testicular function and impaired function of the HPTA( http:///ijir/journal/v15/n3/full/ ). Clomifene blocks estrogen from binding to some estrogen receptors in the hypothalamus, thereby causing an increased release gNRH and subsequently LH from the pituitary. Clomifene is a Selective Estrogen Reuptake Modulator (SERM). Generally clomifene does not have adverse effects at the doses used for this purpose. Clomifene at much higher doses is used to induce ovulation and has significant adverse effects in such a setting.
There are huge numbers of testosterone creams, pills, and injections as well as ads convincing men they are in need of these products. There are also thousands of lawsuits filed against the manufacturers of the various testosterone therapies claiming the drugs caused several severe cardiovascular side effects including heart attack and stroke. With this knowledge, Men’s Journal published an article describing natural ways men can boost their testosterone through diet so as not to take on unnecessary risks. One suggestion made was to increase vitamin D intake which could increase testosterone level. Men should always use caution and discuss diet changes with their doctor.
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.