[Radioimmunological measurement methods in ambulatory endocrinology]

Measurements of plasma-hormone concentrations can be helpful for differential diagnosis in clinically suspect endocrine disorders. By means of radioimmunological methods a series of hormones can be estimated in small plasma volumes. The assay technique differs from chemical methods routinely used in a clinical laboratory. Reagents and details of immunoassay procedures vary between laboratories, and hence hormone estimations from different institutes cannot be directly compared. The plasma half-life of many hormones is 10-30 minutes. The regulation of hormone secretion is complex. Dynamic tests using a known stimulation or suppression provide a better estimate of the function of an endocrine axis than a single random measurement. Hormone assays should be required and interpreted in close collaboration with the endocrine laboratory, which should provide competent counseling with respect to methodologic and endocrinologic aspects.