THE DIAGNOSIS OF PHEOCHROMOCYTOMA BY DETERMINATION OF URINARY 3-METHOXY,4-HYDROXYMANDELIC ACID*†

Abstract

Recent studies clarified the metabolic pathways for degradation of epinephrine (E) and norepinephrine (NE). They suggested that the diagnosis of pheochromocytoma could be facilitated by analysis for the phenolic metabolite, 3-methoxy,4-hydroxymandelic acid (VMA). A chromatographic technique for measuring VMA was used to study urine samples from 15 normal subjects, 36 patients with primary hypertension, and 30 subjects with pheochromocytoma. Correlative E and NE determinations were performed on most of these samples. VMA analysis was performed as follows: a volume of urine equivalent to 0.5 mg creatinine was acid hydrolyzed, extracted with ethyl acetate, concentrated, and spotted on the corner of a one foot square of filter paper; bidirectional chromatography using isopropanol: water: NH4OH (40:9:1) and benzene: propionic and: water (20:14:1) was followed by color development with diazotized p-nitroaniline. VMA appeared as a purple spot with an Rf of 0.27 (isopropanol system) and 0.15 (benzene system). As little as 0.2-0.3 [mu]g of VMA could be determined. Comparison of the unknown with VMA standards simultaneously spotted on each chromatogram yielded a reproducible quantitative accuracy of [plus or minus] 10%. Normal subjects excreted 0.8-2.0 [mu]g VMA/mg creatinine (mean= 1.4), and those with primary hypertension, 0.7-3.0 [mu]g VMA/mg creatinine (mean= 1.4). Patients with pheochromocytomata excreted 6-40 [mu]g VMA/mg creatinine (mean = 17.6). The ratio of VMA of E and NE was 100:1 in the first 2 groups, and about 10:1 in the last group. The relative ease and reproducibility of VMA urinary analysis along with its diagnostic accuracy make it a useful procedure for the diagnosis of pheochromocytoma.