The assessment of fasting serum
gastrin (FSG) is essential for the diagnosis and management of patients with the
Zollinger-Ellison syndrome (ZES). Although many studies have analyzed FSG levels in patients with
gastrinoma, limited information has resulted from these studies because of their small size, different methodologies, and lack of correlations of FSG levels with clinical, laboratory, or
tumor features in ZES patients. To address this issue, we report the results of a prospective National Institutes of Health (NIH) study of 309 patients with ZES and compare our results with those of 2229 ZES patients in 513 small series and case reports in the literature. In the NIH and literature ZES patients, normal FSG values were uncommon (0.3%-3%), as were very high FSG levels >100-fold normal (4.9%-9%). Two-thirds of
gastrinoma patients had FSG values <10-fold normal that overlap with
gastrin levels seen in more common conditions, like Helicobacter pylori
infection or
antral G-cell
hyperplasia/hyperfunction. In these patients, FSG levels are not diagnostic of ZES, and
gastrin provocative tests are needed to establish the diagnosis. Most clinical variables (
multiple endocrine neoplasia type 1 status, presence or absence of the most common symptoms, prior medical treatment) are not correlated with FSG levels, while a good correlation of FSG values was found with other clinical features (prior gastric surgery,
diarrhea, duration from onset to diagnosis). Increasing basal
acid output, but not maximal
acid output correlated closely with increasing FSG. Numerous tumoral features correlated with the magnitude of FSG in our study, including
tumor location (pancreatic > duodenal), primary size (larger > smaller) and extent (liver
metastases > local disease). In conclusion, this detailed analysis of FSG in a large number of patients with ZES allowed us to identify important clinical guidelines that should contribute to improved diagnosis and management of patients with ZES.