Norethisterone Androgenic Activity

Norethisterone has about 15% of the affection of the anabolic–androgenic steroid (AAS) metribolone (R-1881) for the AR, and in accordance, is abominably androgenic. In adverse to Norethisterone, 5α-DHNET, the above metabolite of Norethisterone, shows college affection for the AR, with about 27% of the affection of metribolone. However, although 5α-DHNET has college affection for the AR than Norethisterone, it has decidedly beneath and in actuality about abolished androgenic authority in allegory to Norethisterone in rodent bioassays. Similar allegation were empiric for ethisterone (17α-ethynyltestosterone) and its 5α-reduced metabolite, admitting 5α-reduction added both the AR affection and androgenic authority of testosterone and nandrolone (19-nortestosterone) in rodent bioassays. As such, it appears that the ethynyl accumulation of Norethisterone at the C17α position is amenable for its accident of androgenicity aloft 5α-reduction.

Norethisterone (0.5 to 3 mg/day) has been begin to dose-dependently abatement circulating SHBG levels, which is a known acreage of androgens and is due to AR-mediated abolishment of hepatic SHBG production.The biologic aswell has estrogenic activity, and estrogens are known to access SHBG hepatic assembly and circulating levels, so it would arise that the androgenic activity of Norethisterone overpowers its estrogenic activity in this regard.

Norethisterone is apprenticed to a ample admeasurement (36%) to SHBG in circulation. Although it has lower affection for SHBG than autogenous androgens and estrogens,Norethisterone may displace testosterone from SHBG and thereby access chargeless testosterone levels, and this activity may accord to its anemic androgenic effects.