The first menstrual period is a sign that a woman has reached puberty and the beginning of the cyclical regulation of her reproductive organs. The physiological changes of menstruation are a very complex process, and this cyclical change is described here very briefly. Generally speaking, the menstrual cycle lasts 28-30 days, and it may be normal to advance or postpone it. As long as the corresponding cyclic changes occur in the body, especially in the pituitary gland and ovaries, there is usually no need to adjust a slightly shorter or longer menstrual cycle. The pattern of the menstrual cycle is roughly like this. Starting from the onset of menstruation, along with the gradual development of follicles in the ovaries, estrogen synthesis increases. An important function of estrogen is to repair the endometrium, which is complete, and menstruation stops, after which the amount of estrogen continues to increase and the endometrium continues to thicken. You will feel an increase in vaginal discharge, sometimes it is obvious that the discharge is like egg white, transparent, sticky and can be stretched to a long length, which is a sign that the follicle is well developed and about to mature. In the early stage of follicle development, there are usually more than a dozen follicles competing for development together, and in general, only one has the best chance to develop, called the dominant follicle, and only the dominant follicle has the hope to develop in a menstrual cycle Mature ovulation, ovulation usually occurs 14 days before the next menstrual period and some people who are more sensitive may feel a sore, swollen, falling sensation in their lower abdomen. Sometimes there is a very small amount of vaginal bleeding during ovulation, called ovulatory bleeding, and these are normal. The clear egg-white like discharge disappears immediately after ovulation, when the estrogen level is low. An important change after ovulation is the formation of something called corpus luteum at the rupture left after ovulation on the ovary. The corpus luteum synthesizes estrogen and progesterone, which is a progesterone, and under the influence of these two hormones, the endometrium remains thick and hydrated in preparation for the possible fertilization of the egg, as if the soil should be loosened and fertilized before planting, which facilitates the planting of the pregnant egg. During this period, as hormone levels increase, breast tenderness may occur, because if no conception occurs, the corpus luteum only lasts for about 14 days, and this thick lining needs a lot of hormonal support. Therefore, the onset of menstruation is caused by a decrease in hormone levels. Therefore, prolonged menopause and progesterone treatment is given in response to an endometrial secretion, and a decrease in hormone levels occurs after stopping the medication, simulating hormonal withdrawal bleeding, where vaginal bleeding occurs several days after stopping the medication, not during the period of taking the medication.