Effect of short-term treatment with low dosages of the proton-pump inhibitor omeprazole on serum chromogranin A levels in man

Background: Measurement of chromogranin A (CgA) levels in blood can be used to monitor neuroendocrine tumors (NETs). CgA levels may also be elevated in several other endocrine and non-endocrine diseases. It is well known that drugs affecting acid gastric secretion can increase gastrin. Protonpump inhibitors are extensively used but only a few data have been reported on their effects on CgA secretion. Design: The aim of the study was to evaluate the short-term effect of low dosages of omeprazole (OM) on CgA levels and to sensitize endocrinologists to possible false positive values of CgA in order to prevent expensive diagnostic work-up in searching for NETs. Subjects and methods: Thirty-five female and nine mate in-patients (18-81 years) were studied. Mild or severe hypertension in 20 patients needed therapy Endocrine and metabolic diseases were diagnosed in the majority of patients. CgA levels were evaluated before and during OM therapy (10 mg/day, orally). Results: Without OM therapy, CgA levels were 64 +/- 6 mug/l. Elevated baseline CgA levels were found in nine subjects. CgA levels were significantly related to age (P < 0.001), creatinine levels (P = 0.03) and the severity of hypertension (P = 0.002). On short-term OM therapy (n = 42; 18.8 +/- 2.4 days: range 5-90 days) a significant (P<0.001) increase in CgA (145+/- 22mug/l) from baseline (63+/-7mug/l) levels was found. The average net CgA increase on short-term OM therapy was 93+/-20mug/l. There was a significant correlation between baseline CgA levels and CgA increase on short-term OM therapy (P = 0.004) but not between the increase in CgA and the duration of the therapy. Conclusions: An increase in CgA levels quickly follows the start of low dosages of OM. This release is more pronounced when the baseline CgA levels are already increased by slight renal insufficiency or severe hypertension. In this common clinical situation an intensive work-up for NETs is not justified before reassessment of CgA after the withdrawal of OM.