Review of the influence of polypeptide hormone forms on immunoassay results

Various forms of the polypeptide hormones that occur in blood, fluids, or tissues can differ according to physiologic and pathologic states. Forms include subunits of luteinizing hormone, follicle-stimulating hormone, human chorionic gonadotropin, and thyroid-stimulating hormone. Hormonal isoforms occur for these hormones as well as for prolactin and growth hormone. Variation in hormonal forms appears to contribute significantly to the wide variation in immunoassay results for these polypeptide hormones. Subunits and isoforms of the polypeptide hormones can overreact or underreact in monoclonal antibody assays. The underreaction or overreaction can occur with standards, controls, and patient specimens as well as with the assay label.