GASTRIN ASSAY - Gastrin is a hormone that is produced by specialized cells in the stomach. When there is food in the stomach, these cells secrete gastrin. Gastrin then stimulates the stomach parietal cells to produce hydrochloric acid. Normally, as stomach pH lowers, gastrin secretion decreases. Gastrin blood levels can be determined to be elevated in conditions such as Zollinger-Ellison syndrome and pernicious anemia.