Ethisterone is a progestational steroid with therapeutic uses similar to those of progesterone—that of treating cases of threatened and habitual abortion and endometriosis. However, it also has estrogenic and androgenic properties, and its usefulness has been recently limited; the drug has largely been replaced in the therapeutic armamentarium. It has been available by prescription under the trade names Pranone®, Ora-Lutin®, Progesteral®, and Lutocylol®, among other names. It has a pregnancy category of D. In laboratory animals, ethisterone caused masculinization of female fetuses in both rats and rabbits. In the human, as with some other progestational agents, virilization of female issue were recorded in 78 cases. Ethisterone is a larger hydrophobic human developmental toxicant. Structurally it differs from norethindrone by the presence of an additional methyl group. Ethisterone is of lower polarity and it can engage in hydrogen bonding.