Laura M. Bertani

The biochemical techniques for detecting and establishing the presence of a pheochromocytoma. A review of ten years' experience.

Abstract Pheochromocytoma, fatal if undetected, is a rare cause of hypertension, paroxysmal symptoms and a hypermetabolic state. The clinical signs and symptoms associated with this tumor rarely result in its detection. Advances in knowledge of catecholamine metabolism have markedly improved the diagnostic reliability for tumors of the neural crest. Large numbers of patients must be screened and the diagnosis ultimately proved by biochemical assays for the catecholamines and their catabolites, vanillylmandelic acid, total metanephrines, 3-methoxy-4-hydroxyphenylethyleneglycol and homovanillic acid. Many assay procedures are nonspecific, and therefore do not reliably differentiate the rare patient with pheochromocytoma from patients with more common maladies. We reviewed laboratory screening procedures in 92 subjects with proved pheochromocytoma and 9,500 control subjects. Excretion of the total metanephrines, although uniformly increased in the presence of a pheochromocytoma, was occasionally increased in its absence. Vanillylmandelic acid excretion, rarely increased in the absence of a neural crest tumor, was within normal limits in about 3 percent of patients with pheochromocytomas. Nonspecific techniques for colorimetric assay of vanillylmandelic acid, now widely used, had little diagnostic value in over 30 percent of cases of pheochromocytoma. Familiarity with the various biochemical procedures for assay of the catecholamines and their catabolites is essential in establishing a diagnosis of sufficient reliability to warrant surgical exploration.

Diagnosis of neuroblastoma by qualitative and quantitative determination of catecholamine metabolites in urine

Neuroblastoma, one of the most common solid malignant tumors of childhood, has been frequently confused with other malignancies as well as nonneoplastic diseases. The observation that neural crest tumors resulted in excretion of elevated quantities of the catecholamines and their by‐products opened the way for development of biochemical techniques for their detection. Vanillylmandelic acid, metanephrines, homovanillic acid, and 3‐methoxy‐4‐hydroxy‐phenylethyleneglycol excretions of 180 normal children were compared with those of 62 subjects suffering from illnesses commonly confused with neuroblastoma as well as 41 patients with neural crest lesions. A simple, bedside chemical technique for detecting a neuroblastoma resulted in no false positive and 91% reliability among those patients with this tumor. Although quantitative assay for 3‐methoxy‐4‐hydroxyphenylethyleneglycol appeared to offer the greatest reliability for biochemical diagnosis of neuroblastoma, broad application of the screening test might significantly improve the ease of detection and differential diagnosis of neuroblastoma.

A gas-liquid chromatographic method for the separation and quantitation of normetanephrine and metanephrine in human urine

Abstract A gas-liquid Chromatographic method for the separation and quantitation of urinary normetanephrine and metanephrine as their trifluoroacetyl derivatives is presented. After a preliminary column separation of basic from neutral and acidic compounds in hydrolyzed urine, the trifluoroacetylated amines (normetanephrine, metanephrine, octopamine, tyramine, 3-methoxytyramine, tryptamine and serotonin) were separated on a 1:1 w/w (3% QF-1: 2% XF-1105) column. An electron capture detection system was employed for maximal sensitivity. Normal human urinary values for normetanephrine ranged from 0.086 to 0.177 μg/mg creatinine (mean = 0.116 ± 0.029) and for metanephrine ranged from 0.059 to 0.145 μg/mg creatinine (mean = 0.093 ± 0.027). Patients with pheochromocytoma and neuroblastoma had elevated urinary excretions of normetanephrine and/or metanephrine.

Human norepinephrine metabolism: Its evaluation by administration of tritiated norepinephrine

It has become increasingly apparent that evaluation of human norepinephrine metabolism simply by assay of catecholamines in urine is inadequate for differentiation of many physiological or pathological states. In an attempt to examine norepinepherine metabolism in the human subject, tritium-labeled d,l-norepinephrine was administered to 11 normal adults and the definitive turnover rates and relative specific activities of norepinephrine and its major catabolites, vanillylmandelic acid, 3-methoxy-4-hydroxyphenylethyleneglycol, and normetanephrine, as well as the cumulative 24 hr isotope excretion were determined. The major endogenous norepinephrine catabolites were also quantitatively assayed. In order to verify the reliability of the isotope label, parallel studies were carried out in two patients to whom norepinephrine-(14)C was administered. Metabolic studies were repeated after the administration of reserpine to gain further insight into the distribution of the label.All studies demonstrated a consistent difference between the relative specific activities of the amines and their deaminated congeners, thereby indicating an uneven distribution of the labeled material. The marked decrease in the relative specific activities of the deaminated catabolites after the administration of reserpine showed that the present experimental technique succeeded in labeling, though to a limited extent, the storage or reserpine-releasable pool. A dose of reserpine known to interfere with sympathetic activity but failing to elicit a change in excretion of endogenous catecholamine catabolites, nonetheless resulted in a marked abnormality in the metabolic handling of labeled norepinephrine. It is anticipated that such studies may not only be of value in measuring sympathetic activity in the intact human subject during physiologic variations and pathologic states associated with abnormalities in catecholamine metabolism, but may serve as a technique whereby drugs that affect human norepinephrine metabolism may undergo precise pharmacologic evaluation.

Benign pheochromocytoma associated with elevated excretion of homovanillic acid

The excretion of catecholamine metabolites was determined in nine children prior to and following resection of one or more well-encapsulated, benign pheochromocytomas. One third of these subjects presented with increased excretion of homovanillic acid as well as markedly increased excretion of vanillylmandelic acid and total metanephrines: biochemical evidence opposed to the presence of a benign pheochromocytoma. No significant difference in age, sex, clinical presentation, course, or postoperative biochemical evaluation could be detected between this group and the six remaining subjects. Elevated homovanillic acid excretion, indicative of the presence of a malignant pheochromocytoma in the adult, does not carry this serious prognostic import in childhood. In childhood, elevated homovanillic acid and markedly increased excration of vanillylmandelic acid and total metanephrines, usually associated with neuroblastoma, do not rule out the diagnostic possibility of a benign pheochromocytoma.

Modification of the taniguchi method for the determination of normetanephrine and metanephrine

Abstract Using tritium-labeled normetanephrine enables one to determine the exact point at which this substance is completely eluted from the adsorbing resin into borate buffer. With this refinement the Taniguchi method gave good results for the determination of normetanephrine and metanephrine.