Endocrine Abstracts

BACKGROUND: Patients with dyspepsia are treated with proton pump inhibitors (PPIs) which reduce acid secretion and therefore give rise to a secondary hypergastrinaemia. Gastrinomas are a rare cause of dyspepsia diagnosed on the basis of a raised fasting gastrin measurement. Therefore, when screening patients with dyspepsia for a gastrinoma, PPIs must be withdrawn for 2 weeks, prior to the measurement of fasting gastrin levels to ensure that fasting gastrin levels are back to basal levels. In patients in whom a gastrinoma is confirmed the risks of gastrointestinal perforation when stopping antisecretory medication in order to measure fasting gastrin levels is high.

AIM: To investigate if a gastrinoma can be diagnosed by measurement of fasting plasma gastrin in patients who remain on PPI therapy.

METHODS: Plasma gastrin results were analysed in four groups of patients: controls taking no antisecretory medication (n=46), patients without a gastrinoma on PPIs (n=14), patients with a gastrinoma on no medication (n=14) and patients with a gastrinoma on PPIs (n=10).

RESULTS: Patients without a gastrinoma taking PPIs had a significantly higher fasting plasma gastrin level compared to patients without gastrinomas taking no medication (mean plus/minus SEM, 204 plus/minus 31pmol/l, vs. 12 plus/minus 2pmol/l, p <0.0001). There was no significant difference between patients without gastrinomas taking PPIs and patients with a gastrinoma taking no medication (mean plus/minus SEM, 203 plus/minus 31pmol/l vs. 193 plus/minus 31pmol/l, p = 0.745). Patients with a gastrinoma on PPI therapy had a significantly higher fasting plasma gastrin concentration (mean plus/minus SEM, 298 plus/minus 35pmol/l) than patients without a gastrinoma on PPI therapy but there was an overlap between these two groups.

CONCLUSIONS: Our data confirms that gastrinomas cannot be diagnosed on the basis of a fasting plasma gastrin measurement whilst patients remain on PPI therapy.