Estrogen is one of the sex hormones secreted by the human body. Female estrogen is mainly responsible for the development of the female body, including pregnancy, and has many manifestations in molecular form, such as estradiol, progesterone and progesterone. In men, the metabolic process also produces part of estrogen, estradiol, and the high or low level of estradiol may be related to male sexual desire, including some physical performance. If estrogen is too high in the male, it will suppress the secondary sexual characteristics of the male, and if it is high, it will also affect the specific functions of the reproductive system, including erectile function and spermatogenesis of the testes. Estrogen is more important for women, but for men it is only a metabolite, which is related to testosterone. The metabolite after testosterone is estradiol, and the level of estradiol shows whether the metabolism of testosterone is normal or not. Estradiol is an observational indicator, but not the main indicator for various male functions.