Estrogens (or oestrogens) are a group of steroid compounds that function as the
primary female sex hormone. They are produced primarily by developing follicles in
the ovaries, the corpus luteum and the placenta. Some estrogens are also produced in
smaller amounts by other tissues such as liver, adrenal glands and the breasts.
These secondary sources of estrogen are especially important in post-menopausal
women.
The three naturally occurring estrogens are estradiol, estriol and estrone. In the
body these are all produced from androgens through enzyme action. Estradiol is
produced from testosterone and estrone from androstenedione. Estrone is weaker than
estradiol, and in post-menopausal women more estrone is present than
estradiol.
While estrogens are present in both men and women, they are found in women in
significantly higher quantities. They promote the development of female secondary
sexual characteristics, such as breasts, and are also involved in controlling the
menstrual cycle, which is why most birth control pills contain estrogens.
The use of estrogen, especially together with progesterone, is a controversial
treatment for the symptoms of menopause which may do as much harm as good.
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