The thalamic-pituitary-ovarian axis is a very sophisticated regulatory system in the female body, of which ovarian secretion of estrogen is an important part to ensure female health. When estrogen levels decrease, the system sends signals to the thalamus and pituitary gland to secrete the hormones that cause the ovaries to secrete sex hormones, such as folliculopoietin FSH and LH. When estrogen levels decrease, these two indicators also increase, and if estrogen is restored, these two indicators decrease, and they regulate each other. When estrogen levels decrease, pituitary secretion of FSH increases, and FSH stimulates follicle growth in the ovary, which secretes estrogen to perform its function of protecting human health. In fact, during menopause, estrogen levels do not decline because when estrogen levels decline, the thalamus-pituitary gland secretes large amounts of FSH to force follicles to grow, and the few follicles that do grow and develop at this time continue to secrete estrogen to maintain high levels of estrogen, so during menopause, FSH is elevated while estrogen levels do not Therefore, during menopause, FSH is increased while estrogen levels do not decrease. When FSH and LH continue to increase until they reach their limits and the follicles are depleted and can no longer grow, then the estrogen level drops very low. This is the difference between menopause and amenorrhea, and the difference between menopause and amenorrhea is determined by the very high FSH and LH values rather than by the estrogen values. Amenorrhea is due to a factor that causes the absence of menstruation rather than ovarian failure. If the pituitary gland function is reduced and FSH and LH decrease, it may be amenorrhea. When FSH and LH are high and estrogen levels are also low, the diagnosis is menopause, which is the differential diagnosis and the change in hormones in the body before and after menopause. This is the differential diagnosis, which is the change of hormones in the body before and after menopause. Therefore, clinically, it is necessary to take blood tests to determine whether perimenopause is present.