Recently, hypoglycemia with endogenous hyperinsulinemia has been described after undergoing bariatric surgery because of morbid obesity. It has been theorized that after a gastric bypass surgery, some trophic factors affecting pancreatic beta cells could emerge. The authors present a case of morbidly obese patient with severe hypoglycemia 3 months after bariatric surgery. An abdominal helicoidally computed tomography scan showed a 1.7 cm tumor in the tail of the pancreas. Histopathology revealed an insulinoma with well-defined contours surrounded by pancreatic tissue with atrophic signs and with hyperplasia and hypertrophic phenomena compatible with nesidioblastosis in adjacent islets of the pancreatic duct. Authors hypothesize that maintenance of the stimulus produces hyperplasia/hypertrophy of the pancreatic islets and reemphasizes the dynamic qualities of pancreatic beta cells and the possibility of producing hyperplasia from the extreme resistance to insulin present in morbidly obese patients.