ATC code L02BA MeSH D020847 | Biological target Estrogen receptor | |
Synonyms Estrogen antagonists; Estrogen blockers; Estradiol antagonists Use Breast cancer; Infertility; Male hypogonadism; Gynecomastia; transgender men Chemical class Steroidal; Nonsteroidal (triphenylethylene, others) | ||
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. Antiestrogens are one of three types of sex hormone antagonists, the others being antiandrogens and antiprogestogens.
Contents
Types and examples
Antiestrogens include selective estrogen receptor modulators (SERMs) like tamoxifen, clomifene, and raloxifene, the ER silent antagonist and selective estrogen receptor degrader (SERD) fulvestrant, aromatase inhibitors (AIs) like anastrozole, and antigonadotropins including androgens/anabolic steroids, progestogens, and GnRH analogues.
Although aromatase inhibitors and antigonadotropins can be considered antiestrogens by some definitions, they are often treated as distinct classes. Aromatase inhibitors and antigonadotropins reduce the production of estrogen, while the term "antiestrogen" is often reserved for agents reducing the response to estrogen.
Medical uses
Antiestrogens are mainly used as a means of estrogen deprivation therapy in the treatment of ER-positive breast cancer. They are also used to treat infertility, male hypogonadism, and gynecomastia (breast development in men) and are used as a component of hormone replacement therapy for transgender men.
Side effects
Side effects of antiestrogens include hot flashes, osteoporosis, breast atrophy, and vaginal dryness and atrophy.
History
Ethamoxytriphetol (MER-25) was the first antiestrogen to be discovered, followed by clomifene and tamoxifen.