Menstruation is the process of cyclical proliferation and exfoliation of the endometrium under the action of estrogen and progesterone secreted by the ovaries. The normal menstrual cycle is between 21-35 days. To have regular menstruation, the ovaries must be able to secrete estrogen and progesterone normally. In order to have regular menstruation, there must be a certain amount of estrogen, so that the thickness of the endometrium reaches a certain level, otherwise the simple use of progesterone can not achieve the purpose of making menstruation. That is, when the endometrium reaches a certain thickness, progesterone can be used, such as oral dextroprogesterone tablets, progesterone gel pills, or intramuscular injections of progesterone, which can transform the endometrium from the proliferative phase to the secretory phase, which in turn leads to vaginal bleeding. If the lining of the uterus is thin, artificial cycle therapy, i.e., estrogen and progesterone supplementation, may be needed to bring on menstruation. There are many reasons for delayed menstruation, such as premature ovarian failure, polycystic ovary syndrome, etc., and the cause of the problem needs to be clarified and actively treated.