Catecholamine and Metanephrine Testing

Pheochromocytomas arise from adrenal chromaffin cells, while paragangliomas arise from related tissue outside the adrenal gland. Both may produce catecholamines, especially epinephrine and norepinephrine, which can cause episodic or sustained vasoconstriction, tachycardia, sweating, tremor, and severe hypertension. Catecholamines may be released in bursts. Measuring a single catecholamine concentration can therefore miss a tumour between episodes. Metanephrines are the metabolites produced as catecholamines are broken down: epinephrine becomes metanephrine, and norepinephrine becomes normetanephrine. These metabolites are produced more continuously, making them more useful biochemical markers. For suspected pheochromocytoma or paraganglioma, the preferred initial tests are: - plasma free metanephrines, or - 24-hour urinary fractionated metanephrines. Plasma free metanephrines are especially sensitive when testing follows discovery of an adrenal mass or when a person has a known genetic predisposition.