Menopause is defined as the cessation of menstrual periods in women that occurs at about age 50 years. It is associated with a marked decline in oocyte number that is attributable to progressive atresia (absence) of the original complement of oocytes, secondary to a genetically programmed loss of ovarian follicles. Unlike the age of menarche (the beginning of the first menstrual period), which is affected by nutritional status and general health, the age of menopause has not changed since ancient times. Genetic variation in the estrogen receptor gene appears to be one determinant of the age of menopause. Among 900 postmenopausal women in the Netherlands, the mean age at menopause varied by 1.1 year among women with different alleles at the same locus of the estrogen receptor gene. Despite the prolongation of human life through the centuries, the outcome of menopause is almost unchanged.

The climacterium is the whole transitional period...