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)