Estrogen blockers (Tamoxifen) are often used to treat breast cancer with estrogen sensitive tumors in premenopausal women. Yet there are problems such as an increased rate of uterine cancer and clotting problems. In postmenopausal women, most estrogen does not come from the ovary; it comes from estrogen production in fat tissues and from the conversion of testosterone and androstenedione into estrogens. Aromatase inhibitors such as Arimidex, Femara, or Aromasin, block this conversion and lower estrogen levels in postmenopausal women. Xenoestrogens are discussed.
