In general, Bhasin says, doctors should give more information to patients considering the treatments. For example, he says, "doctors don’t tell you that testosterone supplements may end up a long-term proposition." When men begin using a supplement, he explains, they typically lose the ability to create testosterone on their own. So if a health problem should arise that forces them to stop taking the supplements, it may take months or years to recover the ability to create adequate levels of testosterone naturally, during which time they may experience withdrawal symptoms like poor mood and low vitality.
“I find it very distressing that testosterone is used in middle-aged men — when we don’t know whether it’s even safe — for something that may be a normal physiologic adaptive mechanism to aging," he says.
Both experts agree that men with a history of heart attack or stroke should steer clear of testosterone supplements. They also agree that there are scenarios in which the benefits of testosterone therapy nearly always outweigh the risks, like hypogonadism, a disease in which the body produces little or no hormone due to poorly functioning testes or pituitary or hypothalamus glands.
Because the relationship between long-term androgen use and gynecological health is not yet fully understood, and because many trans men often experience embarrassment and/or access issues over obtaining ongoing gynecological care, some may feel it is appropriate to pursue such surgeries as a preventative measure. Always discuss the latest medical research and the pros and cons of these procedures with your doctor. For more information on hysterectomy, oophorectomy, PCOS, endometrial cancer, and ovarian cancer see the hysterectomy and oophorectomy page on this web site.
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.