Sex hormones in the aging female.

Aging of the human ovary results in a gradual diminution in ovarian steroid production, followed by an abrupt and almost complete cessation of both estrogen and progesterone production at the menopause. Although carefully controlled quantitative studies have not been published, it appears that the human reproductive axis still retains its ability to respond to steroid action. However, it still remains to be determined if alterations in cycle length and regularity preceding the menopause are due to changes in ovarian function or to subtle changes in the hypothalamic pituitary axis. More experimental evidence is available to describe the etiology of age-related reproductive dysfunction in laboratory rodents. From these studies, it appears that hypothalamic dysfunction is the principal cause for cessation of reproductive cycles. Recent evidence suggests that aging of the hypothalamus is due to cumulative effects of estrogen exposure over the course of the reproductive life span.