Estradiol (estradiol), also known as “estrogen”, “couture hormone”. There are two types, alpha and beta, one type of estrogen. The most content and the strongest activity. Secreted by granulosa cells of ovarian follicles. Its metabolites are estrone and estriol. Contains 18 carbon atoms. Its target organs are the uterus, vagina, fallopian tubes and pituitary gland. Can be used as a transdermal estrogen therapy. Supplements the lack of 17-beta estradiol secreted by women’s ovaries, while avoiding side effects caused by oral administration (breast pain, weight gain, high blood pressure, gallstones and abnormal liver function, etc.). Estrogen can induce cells to synthesize DNA, RNA and various proteins in corresponding tissues.