PIP: The menopause is centered on the ovary and its in-built obsolescence. The events of the menopause start when the active ovary begins to fail and end when the ovary lapses into inactivity. The duration of these events is variable. Stimulated by the pituitary, 1 follicle develops each month as a hormone-producing organ. The life span of the follicle is then 28 days. Follicles continue to develop unt il none respond to the stimulus of the pituitary. The 32-week fetus has about 7 million primordial follicles. At birth, the number has dropped to 2 million. By puberty only 300,000 3008000 remain. During adult life about 400 follicles will have provided the ova and the hormones. The last few capable of funtion may have poor endocrine function. Ovarian activity is controlled by a "biological clock" in the hypothalamus. This controls the pituitary by a gonadotropin-releasing h ormone. In response the pituitary secretes follicle stimulating hormone (FSH) and luteinizing hormone (LH). The creation of the corpus luteum follows in the ovary and secretes progesterone while estrogen secretion continues. A cyclic drop in pituitary gonadotropin secretions causes the corpus luteum to degenerate. The ovary makes estrogen from cholesterol, converting it to pregnenolone, then to progesterone which is androstenedione to andnostenedione and on to estradiol. Estradiol is the estrogen secreted by the ovary, but it can be changed in the liver t o estrone and estriol. The pathways of the steroid hormone synthesis are the same in the adrenal cortex. When estrogen deficiency occurs in the menopause LH levels increase. Later the FSH is raised and remains high for the rest of life. This raised FSH and low estrogen levels appear to cause the characteristic hot flashes. Abrupt deprivation of estrogen causes more symptoms than a slow decline of function. Estrogen therapy may relieve these symptoms. Prevalence of coronary thrombosis rises sharply in the postmenopausal years. Estrogen-containing pills increase the incidence of venous thrombosis. Estrogen therapy reverses the atrophy of the genital tract. Cycles of treatment imitate the normal action of the functioning ovary but usually are not large enough to promote menstruation. Endometrial cancer appears to be increased by estrogen therapy. It may be that the addition of progesterone would protect against this from of cancer. The adjustment of tissues to an altered hormonal environment and the unrelated changes of aging make complicated problem.