It is important to understand each sex hormone in the body so that you realize why testosterone replacement therapy is so effective. Here are just a few of the most important hormones in the body for men and women:
Testosterone. Because this is the male sex hormone it is crucial to the proper functioning of many body systems in men. In women, testosterone is also needed for endocrine system balance.
Estrogen. This is the main female sex hormone needed to develop characteristics in the body. Without proper levels of estrogen, breast development, hip distribution, as well as arm and abdominal muscle definition would not be possible. For this reason, estrogen therapy is common for transgender conversions.
Anti-Androgen. As you may have guessed, this hormone is used to deliver the opposite effects of testosterone. In the body, anti-androgen lowers testosterone production and thus helps to balance sex hormones. Ideal as a hormone therapy for transgender men to women transformations.
Progesterone. There is very little clinical evidence to support progesterone however, it is still used in transgender hormone therapy.