Luteinizing hormone is secreted by the pituitary gland and plays a very important role in promoting ovulation, estrogen and progesterone formation and secretion. 1. Promote ovulation: In the follicular stage, when estrogen is synthesized, luteinizing hormone can provide the substrate (androstenedione) until the follicle develops into the middle or late stage. 2. Promote the formation of estrogen and progesterone: luteinizing hormone can stimulate the expression of progesterone receptor in the dominant follicular granulosa cells, promote follicular luteinization and progesterone production, slowing down the proliferation of granulosa cells, and at this time, progesterone can strengthen the positive feedback effect of estrogen, so that the luteinizing hormone peaks in the middle of menstruation. 3. Promote the secretion of estrogen and progesterone: after ovulation, the normal maintenance of the luteal phase depends on luteinizing hormone, which promotes the synthesis and secretion of progesterone, estradiol and inhibin A. The level of luteinizing hormone is closely related to the level of ovarian luteinizing hormone. Luteinizing hormone level is closely related to ovarian reserve function, therefore, the role of luteinizing hormone is crucial.