[Comparative study of the estrogenic, antifertility and antigonadotropic effects of modified estrogens]

Estrogen (in uterotropic test on sexually immature female rats), antifertile (in experiments on sexually mature pregnant female rats), and antigonadotropic (in a test on sexually immature male rats) properties of some 2- and 4-bromine and silylsubstituted estradiols were compared in oral administration. 4-silylestradiols expressed marked antigonadotropic effects equal by activity to mestranol standard, and reduced as compared with the standard antifertile and estrogenic properties. 2- and 4-bromide and 2-silylestradiols were weakly active or inactive oral estrogens and possessed no antifertile properties.