 This suggests that ethisterone may not be transformed into ethinylestradiol (17α-ethynylestradiol).5α-Dihydroethisterone (5α-dihydro-17α-ethynyltestosterone), formed by 5α-reductase, is an active metabolite of ethisterone.17α-Ethynyl-3α-androstanediol and 17α-ethynyl-3β-androstanediol, also formed via 5α-reductase, as well as other enzymes, are also potential metabolites of ethisterone.