The Female Reproductive System

Women undergo the menopause at approximately 51 years of age, and the timing of this dramatic physiological change has remained essentially constant since medical records have been kept. The menopause occurs at the time of the exhaustion of the ovarian follicular

reserve. Because the ovarian follicles are not only the source of germ cells, but also are the primary source of estrogens, plasma estrogen concentrations drop precipitously during the postmenopausal years and remain low for the remainder of a woman’s life, unless she chooses to take hormone replacement therapy. In recent years, we have come to appreciate that estrogens are not only

reproductive hormones, but that they are pleiotropic hormones that play roles in a wide variety of nonreproductive functions as disparate as bone and mineral metabolism, memory and cognition, cardiovascular function, and the immune system. Thus, the end of reproductive life has far-reaching implications for women, because the hypoestrogenic state brings so many physiological repercussions. With the substantial increase in the average life span of humans from approximately 50 to 80 years that has occurred during the last century (Chapter 2), and the relatively fixed age of the menopause, the number of women who will spend over one-third of their lives in the postmenopausal state has increased dramatically. It is not surprising then that an increasing number of clinical and basic science studies have focused on understanding fully the physiological changes that accompany the menopause, the mechanisms that drive reproductive aging, and the impact of these changes on women’s health. It is our hope that a better understanding will be important to gerontologists, because the female reproductive system deteriorates early during the aging process, in the absence of pathological changes that often confound gerontological studies. Therefore, concepts derived from our understanding of the menopause and the aging reproductive system may apply to the process of the biology of aging of other systems.