GAST and gastrin-producing neuroendocrine tumor: The four major F-panNENs causing specific syndromes are insulinomas (secretion of insulin leading to hypoglycemia), gastrinomas causing Zollinger Ellison syndrome (gastrin leading to recurrent ulcer disease), glucagonomas (glucagon causing necrotic migratory erythema, undernutrition and diabetes mellitus) and VIPomas causing Werner Morrison syndrome (vasoactive intestinal peptide leading to water diarrhea, hypokalemia and achlorhydria) [17].