Norethindrone tablets are a progestin preparation with strong progesterone-like effects. After taking Norethindrone Tablets, it will act on the uterus and cause a series of changes in the uterus, so that it can be used for contraception or for the treatment of irregular menstruation, endometriosis, dysfunctional uterine bleeding and other diseases. After taking norethindrone tablets, the changes occurring in the uterus mainly include: making the endometrium change from the state of proliferative phase to the secretory phase, and with the metabolism of the drug in the body, the endometrium in the secretory phase undergoes exfoliation and bleeding; it can change the properties of the cervical mucus, making the mucus in the cervical area become sticky, so that sperms are not easy to penetrate, so as to achieve the effect of contraception. It can also be used in the treatment of endometriosis because of its anti-estrogen-like effect and inhibition of endometrial proliferation. The main adverse effects are nausea, dizziness, and weakness, and breakthrough bleeding can occur.