Session: MON 37-82-Pheochromocytoma & Paraganglioma
Poster Board MON-46
Design and Method: We compared urinary metanephrines and catecholamines collected separately during day and overnight in subjects with and without pheochromocytoma. Levels were determined by liquid chromatography tandem mass spectrometry and expressed as μmol per mol of creatinine
Results: Excretion of normetanephrine (NMN) was 43% higher for daytime than overnight urine collections in 138 healthy normotensive and hypertensive volunteers (10.9±3.7 vs 7.6±2.7, p≤0.0001) and 48% higher in 68 patients in whom pheochromocytoma was tested and excluded (13.5±5.4 vs 9.1±3.4 p≤0.001). For metanephrine (MN), daytime excretion was 10% higher than nighttime excretion in volunteers (9.6±3.3 vs 8.7±3.0, p<0.0001) and patients with exclusion of pheochromocytoma (7.4±3.6 vs 6.7±3.1, p≤0.001). Urinary excretion of norepinephrine (NE) was 73% higher for daytime than overnight collections in volunteers (17.2±7.9 and 9.9±5.3) and 85% higher in patients with exclusion of pheochromocytoma (19.8±7.5 vs 10.7±44.6, p<0.0001). Epinephrine (EPI) excretion was 167% higher for daytime than overnight collection in volunteers (1.8±1.6 vs 0.6±0.05, p<0.0001) and 210% higher in patients in whom pheochromocytoma was excluded (2.8±1.8 vs 0.9±0.6, p< 0.001). In contrast, for 7 patients with pheochromocytoma, there were no differences between day to night urinary excretion of NMN (78.8±91.4 vs 74.9±102.0), MN (43.1±101.4 vs 41.1±97.7), NE (49.5±28.0 vs 41.4±32.2) and EPI (14.4±33.7 vs 16.9±43.0).
Conclusions: The lower nocturnal excretion of NMN, MN, NE and EPI in subjects without pheochromocytoma may reduce false positive test results related to daytime stress and activity associated with standard 24-hour collections. Further, since excretion of the analytes in patients with pheochromocytoma shows little difference between day to night collections, lowered upper cut-offs for overnight collections may provide improved diagnostic sensitivity. These potential advantages, coupled with the simplicity of nocturnal urine collections, provide justification for further studies to explore utility of overnight versus 24-hour urine collections for biochemical diagnosis of pheochromocytoma.
Nothing to Disclose: MP, MB, RD, DP, SG, GE
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