When women reach puberty, they experience their first menstruation. But how much do you know about menstruation so far? Why do women have menstruation? It’s important to answer the question of what menstruation is. Menstruation is formed by the periodic shedding and bleeding of the endometrium in response to estrogen and progesterone, so in addition to the blood component, menstruation also has the endometrium. Estrogen and progesterone are secreted by the ovaries. We all know that the growth and development of follicles and their discharge occur in the ovaries, but you may not know that when follicles are growing, they secrete estrogen but not progesterone; while after the follicles mature and are discharged, the part of the cells left in the ovaries can secrete both estrogen and progesterone, i.e. progesterone is only available after ovulation. So what is the effect of estrogen and progesterone on the endometrium? Simply put, estrogen allows the endometrium to grow thicker and blood flow to increase, while progesterone allows the endometrium to be transformed into a state suitable for embryo implantation. If there is an embryo implantation, the ovaries will continue to produce progesterone and estrogen, and the endometrium will always be suitable for embryo implantation and growth without bleeding. If there is no embryo implanted in the lining, the ovaries will no longer produce progesterone and estrogen, and the lining will peel off and bleed, resulting in menstruation. Menstruation does not occur until adolescence because during adolescence, the hypothalamus and pituitary gland, the superior nervous system that regulates hormone secretion by the ovaries, are not mature enough to issue commands to the ovaries. Menstruation ends again in middle-aged and older women because all the follicles in the ovaries are depleted and there are no more available eggs, no more ovulation there is no more estrogen and progesterone cycle, and the endometrium no longer peels off and bleeds periodically. Is it true that women do not become anemic when they bleed every month? Under normal circumstances, menstruation does not easily cause anemia. But a small number of women do become anemic because of heavy menstruation! A normal menstrual flow is 20-80ml and lasts 3-7 days. Some women have normal menstruation duration, but the volume is so high that a sanitary napkin soaks through every 2 hours or so, which is a clear case of excessive menstruation. Some women have a period that lasts for more than 10 days, which is also abnormal. If you find that you usually have very heavy periods and also have symptoms of chronic anemia, such as pale eyelids and face, dizziness, palpitations, and weakness, you should seek prompt medical examination and treatment.