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Facts About Estrogen

    Estrogen is the main sex hormone in women and is essential to the menstrual cycle. The term "estrogen" includes a group of chemically similar hormones: estrone, estradiol and estriol. While estrogens are present in both men and women, they are usually present at significantly higher levels in women of reproductive age. Estrogens are used as part of some oral contraceptives, in estrogen replacement therapy for postmenopausal women, and in hormone replacement therapy for transgender women. They promote the development of female secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle.

    Estrogen is manufactured mostly in the ovaries, by developing egg follicles. In addition, estrogen is produced by the corpus luteum in the ovary, as well as by the placenta. Estrogen controls growth of the uterine lining during the first part of the menstrual cycle, causes changes in the breasts during adolescence and pregnancy and regulates various other metabolic processes, including bone growth and cholesterol levels. Declining or low levels of estrogen can cause physical symptoms including hot flashes, night sweats and vaginal dryness. By the time you reach menopause, you will produce only about one-third the amount of estrogen you produced during your childbearing years. Estrogen therapy may be prescribed for conditions such as delayed onset of puberty, genital atrophy or female hypogonadism (incomplete functioning of the ovaries, creating symptoms such as vaginal dryness, breast atrophy and lower sex drive).

In males, estrogen regulates certain functions of the reproductive system important to the maturation of sperm and may be necessary for a healthy libido.