In the female body, progesterone plays a very important role, as it is responsible for the formation of a healthy endometrium, which becomes a kind of breeding ground for the development of the embryo. The body produces progesterone at certain points of the menstrual cycle, and if the formation of a zygote does not take place, its levels rapidly drop, which causes the endometrium to flake. Norethisterone taken to delay menstrual bleeding supplies the body with progesterone, thanks to which hormone levels do not decrease, and there is no bleeding. Therefore Norethisterone can be used as a treatment capable of postponing the period in the event of particularly important occasions such as sporting tournaments or an important journey.
It is also believed that high doses of Norethisterone can be effectively used in the treatment of breast cancer, although the mechanisms of its action in this case have not been established. It most probably blocks the release of hormones from the pituitary gland, which has an inhibitory effect on tumour growth.