17α-alkylated anabolic steroid 17α-alkylated anabolic steroid a 17α-alkylated anabolic steroid is a synthetic anabolic–androgenic steroid (aas) that features an alkyl group, specifically a methyl or ethyl group, at the c17α position. unlike many other aas, 17α-alkylated aas are orally active and do not require intramuscular injection. however, they uniquely possess a high potential for hepatotoxicity, which simultaneously limits their use. in addition, some have a high risk of gynecomastia due to uniquely high estrogenic activity, although this does not apply to 17α-alkylated aas that are also 4,5α-reduced or 19-demethylated (i.e., that are also dihydrotestosterone (dht) or nandrolone derivatives, respectively). the prototypical example of a 17α-alkylated aas is methyltestosterone (17α-methyltestosterone). structure-activity relationships extension of the c17α alkyl chain longer than an ethyl group abolishes androgenic activity and converts the drug into an antiandrogen, as in topterone (17α-propyltestosterone) and allylestrenol (17α-allyl-3-deketo-19-nortestosterone) (an extended-chain variant of ethylestrenol). conversely, replacement of the c17α alkyl group with an ethynyl group greatly reduces but does not abolish androgenic activity, as in ethisterone (17α-ethynyltestosterone) and norethisterone (17α-ethynyl-19-nortestosterone). similarly to extension of the c17α alkyl chain, extension of the c17α ethynyl chain abolishes androgenic activity, as with dimethisterone (6α,21-dimethylethisterone). dienogest, which is antiandrogenic, features extension of the c17α chain in the form of a cyanomethyl group at the c17α position. list of 17α-alkylated aas testosterone derivatives marketed bolasterone calusterone chlorodehydromethyltestosterone (cdmt) fluoxymesterone formebolone metandienone (methandrostenolone) methandriol (methylandrostenediol) methyltestosterone oxymesterone penmesterol (penmestrol) tiomesterone never marketed chlorodehydromethylandrostenediol (cdma) chloromethylandrostenediol (cma) enestebol ethyltestosterone hydroxystenozole methylclostebol (chloromethyltestosterone) dihydrotestosterone derivatives marketed androisoxazole furazabol mebolazine (dimethazine, dymethazine) mestanolone (methylandrostanolone) oxandrolone oxymetholone stanozolol never marketed desoxymethyltestosterone (dmt) methasterone (methyldrostanolone) methyl-1-testosterone (methyl-δ1-dht) methylepitiostanol methylstenbolone nandrolone (19-nortestosterone) derivatives marketed ethylestrenol (ethylnandrol) mibolerone norethandrolone (ethylnandrolone, ethylestrenolone) normethandrone (methylestrenolone, normethisterone) propetandrol (propethandrol) never marketed bolenol (ethylnorandrostenol) dimethyltrienolone ethyldienolone methyldienolone methylhydroxynandrolone metribolone (methyltrienolone) norboletone (norbolethone) tetrahydrogestrinone (thg)