Generally progesterone <1ng/ml is normal during menstruation. Progesterone secreted by the ovary will change cyclically with the menstrual cycle. Generally, it is normal when the progesterone level is at its lowest during menstruation and reaches the level of the follicular phase, i.e. <1ng/ml. Thereafter, with the formation of the corpus luteum after ovulation, the secretion of progesterone by the corpus luteum gradually increases, and at the time of maturation of ovulation, the secretion of progesterone reaches a peak value, and then gradually decreases until the onset of menstruation. The interaction between estrogen and progesterone secreted by the ovaries can further promote the development of female reproductive organs and breasts, and prepare for pregnancy. Under the action of estrogen and progesterone, the endometrium in the proliferative phase will undergo changes in the secretory phase, and after the withdrawal of estrogen and progesterone, the endometrium in the secretory phase will be shed and menstruation will be formed, and the appearance of regular menstruation is a sign of the maturity of the reproductive function.