<prompt> For which one of the following tumors Gastrin is a biochemical marker :Medullary carcinoma of thyroidPancreatic neuroendocrine tumourPheochromocytomaGastrointestinal stromal tumor  <response>: Ans. is b i.e., Pancreatic neuroendocrine tumor Gastrin is secreted by Gastrinomas.Gastrinomas are neuroendocrine tumors found in the duodenum 50 to 70 pancreas 20 to 40 andOther intraabdominal sites mesentery, lymph nodes, biliary tract, liver, stomach, ovaryExcess gastrin secretion leads to Zollinger Ellison SyndromeAlso, knowVerner-Morrison syndrome caused by secretion ofVasoactive intestinal polypeptide VIP Verner-Morris on syndrome is also known as pancreatic cholera or WDHA syndrome excessive watery diarrhea, hypokalemia achlorhydria 