Endocrine Abstracts

Phaeochromocytomas (PCC) are rare tumours of chromaffin cells that are generally characterised by autonomous production of catecholamines. PCC vary considerably in the relative and total amounts of catecholamines produced and stored, in the overall rates of synthesis and in individual-to-individual differences in sensitivities to catecholamines. It is these differences that contribute to the diversity of signs and symptoms. Thus diagnosis depends on a high index of clinical suspicion along with the biochemical confirmation of excessive catecholamine production. Biochemical diagnosis of PCC is straightforward when the urinary levels of the methylated metabolites of catecholamines (normetanephrine, metanephrine) are well above the levels for patients with essential hypertension. However, problems arise in differentiating the presence of PCC in patients with only moderate biosynthetic activity of the tumour from patients with non-specific stimulated nervous system activity. This becomes particularly relevant when trying to detect PCC in individuals with inherited conditions such as VHL, MEN and NF1. Recent developments in the biochemical diagnosis of PCC include the measurement of plasma free-metanephrines, which exhibit a higher level of diagnostic sensitivity than existing urine tests, particularly in patients with a familial predisposition to PCC. Selection of the most appropriate biochemical tests for PCC should consider a critical appraisal of which patients would benefit from which tests.