In 1961, Ciba and Parke-Davis added the reported association of ethisterone and norethisterone with masculinization of external genitalia of the female fetus to the precautions section of their advertisements to physicians and physician prescribing information.
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In general, pregnane derivatives (progesterone, dydrogesterone, 17α-hydroxyprogesterone caproate, medroxyprogesterone acetate, megestrol acetate, etc.) do not virilize even in high dose; testosterone derivatives (ethisterone) and 19-nortestosterone (norethisterone, norethisterone acetate, etc.) generally virilize, but there are exceptions (e.g. norethynodrel) that do not.