Receptors for peptide hormones. New insights into the pathophysiology of disease states in man.

The first step in the action of polypeptide hormones and many neurotransmitters is binding to receptor sites on the plasma membrane of the cell. These receptors are usually complex, high molecular weight proteins. Using a variety of receptor preparations and radioactively labeled hormones, radioreceptor assays for several hormones have been developed. These have allowed for assay of hormones for which no immunoassay exists. Such assays have shown increased levels of NSILA-s (an insulin-like peptide) in patients with nonpancreatic tumors and hypoglycemia. In disease states, the number or affinity of hormone receptors may be altered, leading to hormone resistant states such as the insulin resistance of obesity. A major factor regulating receptor concentration is the hormone itself. Several hormones seem to accelerate inactivation of their own receptors. Antibodies to membrane receptors are produced in at least three diseases and cause hormone resistance or mimic states of hormone excess.