Aims and background: The aim of our study was to investigate the plasma chromogranin A (CgA) and adrenomedullin (AM) levels in patients with pheochromocytomas.
Methods and study design: We collected blood samples for measurement of plasma CgA and AM in 21 patients with pheochromocytomas, 43 healthy subjects and 26 patients with solid non-functioning adrenocortical adenomas. In 11 patients with pheochromocytomas plasma CgA and AM were measured again four weeks after tumor removal. CgA and AM were measured by means of a novel solid-phase two-site immunoradiometric assay based on monoclonal antibodies (CgA-RIA CT, CIS bio international) and by a specific radioimmunoassay (RIA, Phoenix Pharm. Inc.), respectively.
Results: The mean plasma CgA level (+/- SD) in patients with pheochromocytomas (204 +/- 147.9 ng/mL) was significantly higher (P < 0.001) than that in healthy subjects (41.6 +/- 10.7 ng/mL) and in patients with non-functioning adrenocortical adenomas (47.3 +/- 17.6 ng/mL). The mean plasma AM concentration (+/- SD) in patients with pheochromocytomas (27.5 +/- 10.4 pg/mL) was significantly higher (P < 0.001) than that in HS (13.8 +/- 4.5 pg/mL) and in patients with non-functioning adrenocortical adenomas (16.6 +/- 7.3 pg/mL). Plasma CgA levels correlated with plasma AM levels (r = 0.501; P < 0.02) and with plasma metanephrine levels (r = 0.738; P < 0.0001) in patients with pheochromocytomas. In 11 patients with pheochromocytomas plasma CgA and AM concentrations significantly decreased after tumor removal (P < 0.001 for both). Circulating CgA and AM had a sensitivity of 76.2% and 81%, a specificity of 97.7% and 90.7%, and an accuracy of 91% and 88%, respectively.
Conclusion: This study demonstrates that circulating CgA and AM levels are increased in pheochromocytoma patients compared with healthy subjects and patients with non-functioning adrenocortical adenomas. Moreover, at the time of diagnosis plasma CgA levels correlated with plasma AM levels and with plasma metanephrine levels in all patients with pheochromocytomas. In conclusion, plasma CgA and AM concentrations may represent additional biochemical parameters for clinical monitoring of patients with pheochromocytomas.