From what I understand, changing the methylation of a compound would drastically change how the compound acts in the body.
“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).
[1] 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.”