Measurement of urine vanillyl mandelic acid can help in diagnosis of-

Excessive secretion of catecholamines can be confirmed by measuring metabolites in plasma and/or urine (metanephrine and normetanephrine). There is a high 'false-positive' rate, as misleading metanephrine concentrations may be seen in stressed patients (during acute illness, following vigorous exercise or severe pain) and following ingestion of some drugs such as tricyclic antidepressants. For this reason, a repeat sample should usually be requested if elevated levels are found, although, as a rule, the higher the concentration of metanephrines, the more likely the diagnosis of phaeochromocytoma/paraganglioma. Serum chromogranin A is often elevated and may be a useful tumour marker in patients with non-secretory tumours and/or metastatic disease. Genetic testing should be considered in individuals with other features of a genetic syndrome, in those with a family history of phaeochromocytoma/paraganglioma, and in those presenting under the age of 50 years Ref Harrison 20th edition pg 590