Case report: extreme CgA elevation under PPI confounding assessment of adrenal mass.

Measurement of chromogranin A (CgA) level in blood can be used to monitor neuroendocrine tumours. However CgA level may also be elevated in several other endocrine and non-endocrine diseases. Here, we report on a patient with an incidental left-sided adrenal tumour and elevated CgA level. Adrenalectomy did not confirm clinically suspected diagnosis of pheochromocytoma. Postoperative follow-up was remarkable for a persistently elevated CgA level suspecting another neuroendocrine tumour which could not be detected despite extensive investigations. Finally, it was discovered that continuous proton-pump inhibitor administration for gastro-oesophageal reflux disease had caused a falsely elevated CgA level.