Objective: Proton pump inhibitors (PPIs) are used primarily to treat gastroesophageal reflux disease. Proton pump inhibitor-induced achlorhydria increases circulating gastrin and chromogranin A (CGA). Chromogranin is a widely used biomarker for the diagnosis and follow-up for gut-based neuroendocrine tumors (NETs). Proton pump inhibitor-induced increases in CGA or gastrin may falsely suggest the presence of a NET when none exists. Pancreastatin, a fragment of CGA, is also commonly used to diagnose and follow NETs. We hypothesized that chronic PPI use would increase circulating plasma gastrin, CGA, and pancreastatin levels.
Methods: Thirty patients who used PPIs for 6 months or more (mean ± SD duration, 3.1 ± 2.5 years) and a separate control group of 30 patients who never used antacid medications were prospectively evaluated with plasma gastrin, CGA, and pancreastatin determinations.
Results: Chronic PPI use resulted in significant increases in CGA (15.1 ± 11 vs 131 ± 207 ng/mL; P = 0.005) and significant increases in gastrin (34.8 ± 22.3 vs 167.8 ± 136.2 pg/mL; P = 0.001) compared to controls. In contrast, pancreastatin level in nonusers and chronic PPI users were identical (81.6 ± 36.4 vs 89.4 ± 43.4 pg/mL; P = 0.46).
Conclusions: Pancreastatin levels do not change with chronic PPI use and normal pancreastatin levels may be used to distinguish between drug-induced changes in biomarkers and tumor-related increases in circulating biomarkers.