Test Background In the gastrointestinal tract, somatostatin occurs as a 14 and 28 amino acid peptide. Somatostatin is secreted by the pancreatic islet and the endocrine D-cells in the gastric and intestinal mucosa. It is also found in the extrinsic and intrinsic myenteric and submucosal plexuses. Somatostatin-14 predominates in the gastric and pancreatic D-cells. Somatostatin is generally considered to be a universal inhibitor of gut hormones. In the rare pancreatic neuroendocrine tumour (NET) called somatostatinoma, somatostatin is secreted in excess. Therefore, plasma somatostatin measurements can be used in the biochemical diagnosis of somatostatinomas.
Clinical Indications Suspected gastrinoma/somatostatinoma or Zollinger-Ellison syndrome: hypergastrinaemia, dyspepsia, diarrhoea, steatorrhoea, mixed endocrinopathy VIPoma: watery diarrhoea, hypokalaemia, achlorhydria, hypotension and flushing/vasodilation Glucagonoma: hyperglycaemia refractory to insulin, skin lesions, diarrhoea and stomatitis