Ethisterone (INN, USAN, BAN) (brand names Pranone, Progestoral, Lutocylol, Proluton C, many others), also known as 17α-ethinyltestosterone, pregneninolone, and anhydrohydroxyprogesterone, is a steroidal progestin drug and was the first progestin, as well as the first orally active progestogen (it followed injected progesterone (Proluton), which was marketed in 1934), to be introduced.
It was synthesized in 1938 by Hans Herloff Inhoffen, Willy Logemann, Walter Hohlweg, and Arthur Serini at Schering AG in Berlin, derived from testosterone, and was marketed in Germany in 1939 as Proluton C and by Schering in the U.S. in 1945 as Pranone. Ethisterone was also marketed in the U.S. from the 1950s into the 1960s under a variety of trade names by other pharmaceutical companies that had been members of the pre-World War II European hormone cartel (Ciba, Organon, Roussel).; Ethisterone is described as a relatively weak progestogen, similarly to its analogue dimethisterone. It has strong androgenic effects, and this has limited its use. Because of its potent androgenic activity, ethisterone has been associated with the masculinization of female fetuses in women who have taken it during pregnancy.