Estrogen receptors: physiology and clinical applications.

Abstract

A general survey of estrogen ‘receptors’ in animals and humans is made. (1) Receptors have mainly been described in the immature rat or calf. They are specific estradiol-binding proteins which are present in target organs of the hormone, and characterized by their limited binding capacity, high affinity and very narrow stereo specificity for the ligand. The estradiol ‘receptor’ complex probably stimulates RNA transcription in the nucleus. (2) The regulation of the ‘receptors’ has been approached by measuring the variation of the estradiol ‘receptor’ content of organs, either spontaneously for different periods of life or experimentally following endocrine treatment. The data suggest that estradiol, directly or not, favors the biosynthesis of its own ‘receptor’ in the uterus. In mammary glands, pituitary hormones could also be implied in this regulation. (3) In human beings, similar estrogen ‘receptors’ have been detected in uterus and breast cancer but their physiological variations are practically unknown. These ‘receptors’ are currently used to assay plasma estrogen by radiocompetition and the measure of their concentration in human estrogen dependent tumors might be useful to guide endocrine treatment mainly in breast cancer. In addition, they might be used to test in vitro the efficiency of potential contraceptives or anti-estrogen and to understand the physiopathology of some uterine or mammary ‘receptivity diseases’.