Norethindrone (Norethisterone) is a synthetic progestational hormone with actions similar to those of PROGESTERONE but functioning as a more potent inhibitor of ovulation. It has weak estrogenic and androgenic properties. The hormone has been used in treating amenorrhea, functional uterine bleeding, endometriosis, and for contraception.

Norethisterone是一种19-nortestosterone衍生物，缺少C19甲基团，具有C17乙炔基取代，主要表现出孕激素活性而非雄激素活性，并在较小程度上具有雌激素和抗雌激素活性。[1] 与Org 2058 (100%)相比，NET在孕激素受体结合和转录激活活性方面弱五到八倍，但比孕酮强两倍。NET对雄激素受体（5α-二氢睾酮100%）的结合和转录激活活性分别为3.2%和1.1%，对雌激素受体无活性（雌二醇100%），对糖皮质激素受体的活性低于1%（地塞米松100%）。[2] Norethisterone（1 nM）能分别抑制血清刺激或雌二醇（0.1 nM）诱导的MCF-7增殖41%和34%。[3] Norethisterone（50 nM）在大鼠成骨细胞的增殖、分化和矿化过程中产生显著效果，模拟了雌二醇的效果，并且是通过雌激素受体介导的。[4]

96 well plates are seeded with approximately 1000 MCF-7 cells per well in assay kit medium. Subsequently, the cells are incubated with medium containing charcoal/dextran treated serum for three days. The Norethisterone is then added alone to the wells and incubated for seven days. To mimic continuous combined HRT the cells are treated with an oestradiol (0.1 nM)/ Norethisterone combination for seven days. After incubation for seven days, cell proliferation is measured by using an ATP-chemosensitivity test. In brief, proliferation is quantified by measuring light emitted during the bioluminescence reaction of luciferine in the presence of ATP and luciferase.(Only for Reference)