Endocrine Abstracts

Chronic kidney disease (CKD), with or without dialysis, often prompt biochemical tests for pheochromocytoma diagnosis due to high blood pressure, hemodynamic instability or association with certain genetic syndromes. Our objective was to assess plasma free metanephrine and normetanephrine in CKD disease patients, with or without dialysis.

Methods: Plasma free metanephrine and normetanephrine were measured by an enzyme-linked immunosorbent assay in 42 patients with CKD (23 on hemodialysis, six on peritoneal dialysis and 13 with stage 3–5 CKD but without dialysis), 30 patients with histologicaly proven pheochromocytoma and 43 control hypertensive patients. An adrenal mass was ruled out by an abdominal CT scan in all CKD and control hypertensive patients. As the upper limit of normal for both metanephrine and normetanephrine we used the manufacturer provided values. Values are presented as median (25, 75 percentile). Mann Whitney U test was used for group comparisons. For multiple testing Bonferroni correction was used.

Results: Both free metanephrine and normetanephrine levels were significantly higher in hemodialysis (90 (52, 162) and 303 (154, 356) pg/ml), peritoneal dialysis (69 (32, 100) and 312 (1940, 370) pg/ml) and CKD patients without dialysis (41 (22, 52) and 129 (68, 171) pg/ml) than in control hypertensive group (18 (13, 26) and 54 (25, 74) pg/ml) and significantly lower than in pheochromocytoma group (247 (91, 548) and 1329 (698, 1972) pg/ml). Dialysis patients (hemodialysis plus peritoneal dialysis) have higher plasma metanehprine and normetanephrine than CKD patients without dialysis. 48 and 65% of hemodialysis patients had plasma values of metanephrine and normetanephrine respectively over the manufacturer provided upper limit of normal.

Conclusion: Plasma free metanephrine and normetanephrine levels are frequently elevated in CKD patients, particularly in those on dialysis. Plasma free metanephrine levels rise well in the pheochromocytoma range.