THE NONREPRODUCTIVE YEARS

The climacteric, or perimenopause, is that phase of the aging process in which a woman passes from reproductive to nonreproductive capability (generally age 45–55 years). The perimenopause normally lasts 4 years and is marked by altered ovarian function (e.g., cycle length increases or decreases and anovulation is more common). Menopause is defined as permanent cessation of menstruation following the characteristic altered ovarian function. The physiology of the climacteric requires a brief review of ovarian physiology. Primordial germ cells migrate to the genital ridge by 5 weeks of gestation. Successive mitotic cellular divisions form oogonia, which in turn give rise...