9 - Catecholamines

Abstract

This chapter discusses the measurement of catecholamines. The catecholamines (norepinephrine, epinephrine, and dopamine) may be measured in plasma or urine, either unchanged or in the form of major metabolites—usually, vanillylmandellic acid (VMA) or metanephrine and normetanephrine. The commonest indication for catecholamine measurements in clinical medicine is the biochemical diagnosis of pheochromocytoma. In this case, urinary levels of catecholamines, VMA, and total metanephrines (metanephrine and normetanephrine) are commonly used and will detect all but a tiny minority of catecholamine-secreting tumors. The introduction of sensitive radioenzymatic techniques for the measurement of catecholamines in plasma not only allows the detection of patients with pheochromocytoma but also permits the accurate quantitation of the separate catecholamines in a variety of medical conditions, such as essential hypertension and autonomic insufficiency. The analysis of urinary VMA, metanephrines, and catecholamines in most laboratories is based on long-established spectrophotometric or fluorometric methods. Newer radioenzymatic methods for the measurement of urine catecholamines are also used in some centers.