Estrogen is a sex hormone secreted by the ovaries, the role is very large, is an important sex hormone for women, mainly in the following four aspects: First, the reproductive system estrogen in the reproductive system has a very powerful role, mainly in the following eight points, 1, to promote the development of the uterus and cellular hyperplasia and hypertrophy, so that the uterine myometrium thickening, contraction, improve the sensitivity of the uterine smooth muscle to the contraction of uterine hormone. 2, to promote the endometrium Proliferation and repair of mesenchyme and glands, 3, so that the cervical opening dilation and relaxation, cervical mucus secretion increased, thinning the nature, elastic, easy to pull, conducive to the passage of sperm. 4, to promote the development of the base of the fallopian tubes and contraction, so that the luminal epithelial cell secretion increased, cilia growth, to strengthen its incentive to contraction of the amplitude of the contraction. 5, is the development of the labia fullness and deepening of the coloring. 6, to promote the vaginal epithelial basal layer of cell hyperplasia, the Differentiation and maturation, and superficial epithelial cell keratinization, so that the mucosa thickening, and increase intracellular glycogen content, maintain the vaginal acidic environment. 7, synergistic gonadotropins to promote the development of follicles. 8, the hypothalamus and the pituitary gland for the positive and negative return conditions to control the secretion of gonadotropins, estrogen’s role in the reproductive system is mainly the above eight points. Second, the role of estrogen on the mammary gland: it can promote breast stroma and ducts hyperplasia, nipple nipple Yin set up the initial second new development through the world of pituitary lactogen secretion, prompting the production of milk. Third, the role of metabolism: can promote water and sodium retention, promote hepatic high-density lipoprotein synthesis, inhibit low-density lipoprotein synthesis, reduce the level of circulating cholesterol, maintain vascular tone, but also maintain and promote the metabolism of the bone matrix, promote calcium salts and phosphorus salts in the fracture undertakings to maintain a normal fracture of the bone estrogen and parathyroid hormone to work together to maintain balance. With age, estrogen level if low, can appear atherosclerosis as well as osteoporosis and a series of diseases. Fourth, it can increase the elasticity of the skin, increase the epidermal proliferation of the skin and the blood supply of the skin, so estrogen role is very powerful, mainly the above four points of action.