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Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or inhibiting or suppressing estrogen production .
Aromatase is the enzyme that catalyzes a key aromatization step in the synthesis of estrogen. It converts the enone ring of androgen precursors such as testosterone, to a phenol, completing the synthesis of estrogen. As such, AIs are estrogen synthesis inhibitors. Because hormone-positive breast and ovarian cancers are dependent on estrogen for ...
Gynecomastia is thought to be caused by an altered ratio of estrogens to androgens mediated by an increase in estrogen action, a decrease in androgen action, or a combination of these two factors. [7] Estrogen and androgens have opposing actions on breast tissue: estrogens stimulate proliferation while androgens inhibit proliferation.
It is a mixed agonist and antagonist of the estrogen receptor (ER). Clomifene activates the ERα in the setting of low baseline estrogen levels and partially blocks the receptor in the context of high baseline estrogen levels. [18] Conversely, it is an antagonist of the ERβ. [18] Clomifene has antiestrogenic effects in the uterus. [32]
Those cancers have estrogen receptors (ERs), and are called ER-positive. They may also be called estrogen-responsive, hormonally-responsive, or hormone-receptor-positive. Aromatase is an enzyme that synthesizes estrogen. Aromatase inhibitors block the synthesis of estrogen. This lowers the estrogen level, and slows the growth of cancers.
Anastrozole is used in the treatment and prevention of breast cancer in women. [7] The Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial was of localized breast cancer and women received either anastrozole, the selective estrogen receptor modulator tamoxifen, or both for five years, followed by five years of follow-up. [13]
[82] [107] However, doses of 1 to 5 mg megestrol acetate were previously used in combined birth control pills in combination with the estrogen ethinylestradiol or mestranol. [ 8 ] [ 9 ] [ 32 ] Megestrol acetate is an effective contraceptive by itself at dosages of 0.35 to 0.5 mg/day, but is not effective at a dosage of 0.25 mg/day. [ 7 ]
Benign enlargement of the male breast, whether asymptomatic or painful, is a common condition thought to result from an increased estrogen/testosterone ratio or from heightened estrogenic or reduced androgenic activity via receptor interactions.Tamoxifen is used to prevent and treat gynecomastia.