Norethisterone contains norethisterone, which belongs to a group of medicines called progestogens, which are female hormones. Norethisterone can be used in several different circumstances: • to treat irregular, painful or heavy periods • to treat endometriosis (where tissue from the lining of the womb is present in places where it is not normally found) • to treat premenstrual syndrome (also known as premenstrual tension)