Gastrin testing can be used to investigate patients with achlorhydria or pernicious anaemia and for patients suspected of having Zollinger-Ellison syndrome. Gastrin testing can also be used to diagnose gastrinoma.
Intraluminal stomach pH is the main factor regulating gastrin production and secretion. Rising gastric pH levels result in increasing serum gastrin levels, while falling pH levels are associated with mounting somatostatin production in gastric D cells. Somatostatin, down regulates gastrin synthesis and release. Other, weaker factors that stimulate gastrin secretion are gastric distention, protein-rich foods, and elevated secretin or serum calcium levels. Serum gastrin levels may also be elevated in gastric distention due to gastric outlet obstruction, and in a variety of conditions that lead to real or functional gastric hypo- or achlorhydria (gastrin is secreted in an attempted compensatory response to achlorhydria). These include atrophic gastritis with or without pernicious anaemia; a disorder characterized by destruction of acid-secreting (parietal) cells of the stomach, gastric dumping syndrome, and surgically excluded gastric antrum. In atrophic gastritis, the chronic cell-proliferative stimulus of the secondary hypergastrinemia may contribute to the increased gastric cancer risk observed in this condition.
Gastrin levels are pathologically increased in gastrinoma, a type of neuroendocrine tumour that can occur in the pancreas (20%-40%) or in the duodenum (50%-70%). The triad of non beta islet cell tumour of the pancreas (gastrinoma), hypergastrinemia, and severe ulcer disease is referred to as the Zollinger-Ellison syndrome. Over 50% of gastrinomas are malignant and can metastasise to regional lymph nodes and the liver. About 25% of gastrinomas occur as part of the multiple endocrine neoplasia type 1 (MEN 1) syndrome and are associated with hyperparathyroidism and pituitary adenomas. These MEN 1-associated tumours have been observed to occur at an earlier age than sporadic tumours and often follow a more benign course.
1.0 – 100 ng/L
For suspected gastrinomas: patient off proton pump inhibitors (Omeprazole) for 2 weeks; [off H2 antagonists (ranitidine etc) for 3 days]
Plasma – EDTA
May be requested as part of the following tumour screens:- MEN (Multiple Endocrine Neoplasia); NET (neuro-endocrine tumour).