The estrogens are of a group of hormones synthesized by the reproductive organs and adrenal glands in females and, in lesser quantities, in males. All naturally occurring estrogens, including estradiol, estrone, and estriol, are C₁₈ steroids secreted by the theca interna and granulosa cells of the developing ovarian follicle, corpus luteum, or placenta. Estrogens are also produced by the aromatisation of androgens (male hormones) such as androstenedione and testosterone, in the adipose tissue, liver and skin. The enzyme, aromatase, catalyses the conversion of androstenedione to estrone and testosterone to estradiol. Ovarian cells are stimulated by luteinizing hormone (LH) to increase the conversion of cholesterol to androstenedione. Some of this is then converted to the most potent naturally occurring estrogen, estradiol, which is then released into the circulation. Ovarian granulosa cells are supplied with androstenedione by the thecal cells and that is converted to estradiol, which is primarily secreted...