| α-Anordrin; anordrine|
Anordrin (former developmental code name AF-53), also known as 2α,17α-diethynyl-A-nor-5α-androstane-2β,17β-diol dipropionate, is a synthetic, steroid-like estrogen that is used in China as a postcoital contraceptive. It is marketed in a combination formulation with mifepristone under the brand name Zi Yun. Anordrin is a selective estrogen receptor modulator, with both weak estrogenic and antiestrogenic properties. It binds to the estrogen receptor but does not bind to the androgen receptor or the progesterone receptor. In animals, anordrin has antigonadotropic effects, and in male animals, inhibits spermatogenesis and causes atrophy of the epididymis, prostate, and seminal vesicles. It produces a dihydroxylated active metabolite, anordriol, with similar but more potent estrogenic actions. The abortifacient actions of anordrin in animals are blocked by supplemental estradiol, indicating that it is acting as an antiestrogen rather than an estrogen to exert its effects.