REGESTRONE TABLET contains Norethisterone, which belongs to a group of medicines called Progestogens. It is used to manage heavy menstrual bleeding or abnormal uterine bleeding (that occurs due to hormonal imbalance), painful periods, irregular periods or periods that are more frequent than normal (polymenorrhoea), premenstrual tension, endometriosis (abnormal growth of endometrial tissue of the uterus that causes pain and menstrual irregularities), metriopatheias haemorrhagia (intermenstrual bleeding) and breast cancer. It is also used to delay the menstrual cycle.