17β Dihydroequilenin

17β-Dihydroequilenin, or β-dihydroequilenin, also known as 6,8-didehydro-17β-estradiol, as well as estra-1,3,5(10),6,8-pentaen-3,17β-diol, is a naturally occurring steroidal estrogen found in horses that is closely related to equilin, equilenin, and estradiol, and, as the 3-sulfate ester sodium salt, is a minor constituent (0.5%) of conjugated equine estrogens (Premarin). 17β-Dihydroequilenin has unexpectedly shown a selective estrogen receptor modulator-like profile of estrogenic activity in studies with monkeys, in which beneficial effects on bone and the cardiovascular system were noted but proliferative responses in breast or endometrium were not observed.