Estrogen

Estrogens (also spelt 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 oestrogens are also produced in the adrenals and the breasts, especially in post-menopausal women.

The three naturally occurring oestrogens are oestradiol, oestriol and oestrone. In the body these are all produced from androgens through enzyme action. Oestradiol is produced from testosterone and oestrone from androstenedione. Oestrone is weaker than oestradiol, and in post-menopausal women more oestrone is present than oestradiol.

While oestrogens are present in both men and women, it is 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 oestrogens.