Nongonadal Estrogen and Endocrine Function During the Menopause
Estrogens are an integral component of a complex array of hormonal signals elaborated by the brain, pituitary, and ovary that direct the reproductive process in all mammalian species. In addition to their essential actions on tissues of the female reproductive tract, however, estrogens have more subtle but important actions on many other organs and tissues such as liver, bone, fat, and the vascular system in both sexes. Together with the knowledge that many tissues other than the gonads and placenta actively synthesize estrogens it is now evident that the traditional views gained by study of reproductive biology must be broadened. Indeed, the great diversity of chemical structures having estrogenic activity in both the animal and plant kingdoms suggests that the estrogenic signal may have arisen very early in evolution. Considering the strong but yet ill-defined association of estrogens with neoplastic transformation of target cells, the redundancy of mechanisms for regulating or negating estrogen action (protein binding, progesterone, androgens, and glucocorticoids) may reflect adaptive responses required to cope with a necessary evil. In order to understand the consequences of menopause and aging on estrogen-responsive tissues it is necessary to consider (1) nonovarian estrogen production in relation to other hormones, particularly androgens, (2) estrogen transport, and (3) the cellular mechanism of estrogen action. Each of these subjects will be addressed in turn. Physiological and psycholofical aspects of estrogen action, or lack therreof, are considered by colleagues elsewhere in this volume.
KeywordsPostmenopausal Woman Endometrial Cancer Estrogen Action Scatchard Plot Estrogen Production
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