Hormone receptors and target cell responsiveness.

The present article deals with some basic principles in the mechanism of hormone action. All classes of hormones elicit the majority of their physiological effects via specific receptors which are located in three separate compartments of target cells: cell membranes (peptide and glycopeptide hormones), cytoplasm (steroid hormones) and nucleus (thyroid and steroid hormones). These receptors, although distinctively different in their subcellular localizations share some mutual chemical characteristics which play important roles in the regulation of hormone action. Target cell receptor concentration seems to be one variable by which the magnitude and duration of hormone action is regulated, and is subject to both homologous and heterologous hormonal control. In addition, ligand-receptor interaction and occupancy of the receptors by their respective hormones are important factors that are responsible for regulation of hormone action. A major step towards understanding the physiological role of hormone receptors in man are findings that altered receptor function is involved in pathogenesis of and therapeutic approaches to a variety of diseases.