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. Anti Estrogens Pills are one of three types of sex hormone antagonists, the others being antiandrogens and antiprogestogens. Anti Estrogens Pills are commonly used to stop steroid hormones, estrogen, from binding to the estrogen receptors leading to the decrease of estrogen levels.Decreased levels of estrogen can lead to complications in sexual development. Antiandrogens are sex hormone antagonists which are able to lower the production and the effects that testosterone can have on female bodies.
The anti-estrogenic activity of steroids was tested by subcutaneous and oral administration to estrone stimulated immature mice using the weight change of the uterus as the end-point. Highly active anti-estrogens were found among certain derivatives of progesterone, 17α-acetoxyprogesterone, 19-norprogesterone and testosterone. This activity does not appear to be correlated with other known steroidal biological activities.