Estradiol is a type of estrogen. Estrogen is mainly produced by the ovaries of women and can be used to diagnose the disease after an estrogen test in the blood.1. Ovarian function can be monitored and the cause of amenorrhea can be identified by measuring the level of estradiol. If the patient has amenorrhea, an estrogen test can be performed. If the estrogen level is low, the cause of amenorrhea may be caused by primary or secondary ovarian hypofunction, etc. 2. Estradiol can be used to monitor follicular development. The measurement of estradiol in blood can be used as an indicator of follicular development and maturation. 3. To diagnose whether the patient has ovulated or not, there is no cyclical change in estrogen when there is no ovulation. 4. To diagnose precocious puberty in females, if the development of female 2nd sex characteristics occurs before the age of 8, estradiol levels will often be greater than 275 pmol/L and can be diagnosed as precocious puberty.5. Estradiol can also assist in the diagnosis of polycystic ovary syndrome, etc. The above are the most important purposes of estradiol testing.