Menopause: Learn More

Menopause - the Midlife Transition

The female hormonal cycle is an exquisitely controlled system that includes a number of endocrine organs (i.e., hypothalamus, pituitary, adrenal, thyroid and gonadal tissues); to learn more about this cycle itself, see Normal Menstrual Cycle discussion in the PMS Health Department.

The ovaries in women contain follicles that hold the egg cells. At birth, there are about 500,000 egg cells. By puberty, only about 75,000 eggs are left. Only about 400 to 500 eggs ever reach maturity and get released during adulthood. The rest degenerate over the years.

During the reproductive years, two glands in the brain - called the hypothalamus and the pituitary - work together to generate hormones that cause a new egg to be released from its follicle each month. The follicle then produces the sex hormones estrogen and progesterone, which thicken the lining of the uterus. This enriched lining is prepared to receive and nourish a fertilized egg which could develop into a baby. If fertilization does not occur, estrogen and progesterone levels drop, the lining of the uterus breaks down, and menstruation occurs.

The hormone production in the ovaries begins to decline from the mid-thirties. In the late forties, the process accelerates and hormones fluctuate more, causing irregular menstrual cycles and unpredictable episodes of heavy bleeding - this period of life is known as peri-menopause. By the early to mid-fifties, periods finally end altogether - a transition known as menopause.