[1][2][3][4] Norethisterone is a progestin with additional weak androgenic and estrogenic activity.

[1] 5α-DHNET shows higher affinity for the androgen receptor (AR) compared to norethisterone with approximately 27% of the affinity of the potent androgen metribolone (versus 15% for norethisterone).

[2][5] Similar findings were observed for ethisterone (17α-ethynyltestosterone) and its 5α-reduced metabolite, whereas 5α-reduction enhanced both the AR affinity and androgenic potency of testosterone and nandrolone (19-nortestosterone) in rodent bioassays.

[5] As such, it appears that the C17α ethynyl group of norethisterone is responsible for its loss of androgenicity upon 5α-reduction.

[7] However, the concentrations required are probably too high to be clinically relevant at typical dosages of norethisterone.