Urinary and Plasma Catecholamines and Urinary Catecholamine Metabolites in Pheochromocytoma: DiagnosticValue in 19 Cases

We review our data on the measurementof catecholamines and theirmetabolites in 19 patients with pheochromocytoma. All the assays were specific high-performance liquid chro-matographic procedureswith electrothemical detection. The assay of fractionated metanephnnes was 100 % sensitive. Normal values for both urinary norepinephnne and epineph-rine were found in two asymptomatic patients with pheochro-mocytoma Normal values for 3-methoxy-4-hydroxymandelic acid (VMA) were found in two patients withpureepinephrine-secretingtumors and in one patient with multipleendocnne neoplasia type II. Plasma catecholamines were usually less increased than their urinary counterparts. We recommend the specificmeasurementof norepinephnneand epinephrine as the initial test for patients with suggestivesymptoms,and specificmeasurement of normetanephnneand metanephnne for patientsin whom an adrenal mass is incidentallyfound. We argue against the use of total metanephnnes, total cate-cholamines, and VMA pecause of their lack of diagnostic sensWvfty. Indexing Tenus: hyptenskn/noinsphine/epinaph,ine/no,meffi-nephrlne/metanephrine/electrochemicai detecti on/chromatography, re-Pheochromocytoma-a catecholamine-secreting tu-mor that arises from the chromaffin cells of the sympa-thoadrenal system-is a rare cause of secondary hyper-tension. Its diagnosis is important because the hypertension is usually curable by resection of the tu-mor, whereas the condition is potentially lethal if unde-tected. Biochemical confirmation of excessive catechol-amine production is a prerequisite to definitive diagnosis. Plasma catecholamines can now be measured quite accurately with highly sensitive and specific ra-dioenzymatic or HPLC methods, and their value in the diagnosis of pheochromocytoma has beeti demonstrated (1). The mainstay of the evaluation of hypertensive patients has always been-and stifi is-the measure-ment of the 24-h urinary excretion of catecholamines and catecholamine metabolites (2-6). The most fre-quently used tests are those that measure catechol-aniines, total metanephrines (free plus conjugated), and 3-methoxy-4-hydroxymandelic acid (VMA).