| Description: |
Norethindrone is a synthetic progestin, which mimic the actions of the endogenous ovarian hormone progesterone.Norethisterone, or, is a 19-nortestosterone derivative, that lacks a C19 methyl group and possesses C17 ethinyl substitution, and primarily displays progestational activity rather than androgenic activity and, to a lesser extent, has oestrogenic and anti-oestrogenic activity. Norethisterone (50 nM) induces signi?cant effects on rat osteoblast proliferation, differentiation, and mineralization processes, mimicking the effects of estradiol, which is mediated by estrogen receptor.
Norethisterone displays hormonal properties in vivo. Mean active dose (MAD) of Norethisterone s.c. in progestagenic test (McPhail), androgenic test (Hershberger), estrogenic test (Allen-Doisy), and in a progestagenic and estrogenic test (ovulation inhibition test) is 0.63 mg/kg, 2.5 mg/kg, 4 mg/kg, and 0.235 mg/kg, respectively, and the MAD for orally administration is 0.25 mg/kg, 20 mg/kg, 8 mg/kg, and 12 mg/kg, respectively. Norethisterone shows five- to eight-fold weaker progesterone receptor binding and transactivation activities than the Org 2058 (100%) and two-fold stronger than progesterone. Binding and transactivation activities of Norethisterone for androgen receptor (5α-dihydrotestosterone 100%) are 3.2 and 1.1%, respectively, for estrogen receptor none (estradiol 100%) and for glucocorticoid receptor below 1% (dexamethasone 100%). |
