Gastrin is a major gastrointestinal hormone. It serves to stimulate gastric acid secretion and exists in a number of molecular forms, differing from one another in the length of the polypeptide backbone and in derivatizations of individual amino acids. The three principal forms — G-17, G-34 and G-14 — are named for the number of amino acids which they contain.
Immunoassays for gastrin play an essential role in the identification of Zollinger-Ellison tumors (gastrinomas). These tumors are typically, but not invariably, associated with elevated gastrin levels, gastric acid hypersecretion and peptic ulcer disease.
In fasting subjects, gastrin normally circulates at levels of less than 100 pg/mL, with some day-to-day variability. (A survey of the literature indicates that the upper reference limit is to a considerable extent method-dependent, being as high as 200 or 300 pg/mL for some RIA systems.) Fasting gastrin levels in patients with Zollinger-Ellison syndrome are typically very high, well above the reference range for healthy individuals.
Elevated values are also encountered in other conditions. Where gastric acid secretion is impaired, for example in pernicious anemia, gastrin levels are characteristically (and appropriately) increased. Hypergastrinemia and hypersecretion of gastric acid are also encountered in the absence of pancreatic or duodenal tumors. Thus, hypergastrinemia without gastrinoma may be found in pyloric obstruction with antrum distension, after vagotomy, in the "retained antrum" syndrome, and in some patients with ordinary peptic ulcer disease.
Since roughly half of all patients with Zollinger-Ellison tumors have fasting gastrin levels less than 500 pg/mL, the range for gastrinoma overlaps significantly with the range for other forms of hypergastrinemia. A confirmation procedure is therefore often necessary. This usually involves analysis of gastrin levels following secretin injection, calcium infusion or a test meal. The literature suggests that the secretin test is the most reliable of these follow-up procedures.
The molecular heterogeneity of gastrin has important implications for the design of gastrin immunoassays. Since some gastrinomas secrete only G-17, and others secrete only G-34, it is advantageous to use antibodies that will recognize multiple forms. Use of an overly specific immunoassay carries the risk of missing a tumor.
Expected Values: 13 to 115 pg/mL
Lab units Conversion Calculator. Convert Gastrin level to pmol/L, ng/L, ng/dL, ng/100mL, ng%, pg/mL, mU/L. Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for Gastrin.