Anti-estrogen

Antiestrogens, also known as estrogen antagonists or estrogen blockers, are drugs capable of preventing or hindering part or all of the actions of estrogens. They usually act as "competitive inhibitors."

They work by blocking the estrogen receptor (ER) and/or by inhibiting or suppressing estrogen production. Antiestrogens are one of three types of sex hormone antagonists, the others being antiandrogens and antiprogestins.

They are currently important for their efficacy as a treatment for breast cancer.

Types and examples

Antiestrogens include selective estrogen receptor modulators (SERMs) such as tamoxifen, clomiphene, and raloxifene, the silent ER antagonist, and the selective estrogen receptor degrader (SERD) fulvestrant, inhibitors of aromatase inhibitors (ISA) such as anastrozole; and antigonadotropins such as androgens/anabolic steroids, progestogens, and GnRH analogues.

Although aromatase inhibitors and antigonadotropins may be considered anti-estrogens by some definitions, they are often treated as separate classes. Aromatase inhibitors and antigonadotropins reduce estrogen production, while the term " antiestrogen" often reserved for agents that reduce the response to estrogen 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 used to:

• Estrogen deprivation therapy in the treatment of ER-positive breast cancer
• Induction of ovulation in infertility by anovulation
• Male hypogonadism
• Ginecomastia (male breast development)
• A component of hormone replacement therapy for transgender men

Side effects

• Side effects of antiestrogens include suffocation, osteoporosis, breast atrophy, vaginal dryness and vaginal atrophy. In addition, they can cause depression and reduction of libido.

History

• Etanoxitriphetol (MER-25) was the first antagonist of the emergency room to be discovered, followed by chloromphene and tamoxifen.