Summary

Although insulinoma commonly presents as fasting hypoglycaemia it can rarely present as postprandial hypoglycaemia. We describe a case of insulinoma presenting as postprandial hypoglycaemia and type 2 diabetes mellitus (T2DM). A 60-year-old man presented with a 6 year history of postprandial hypoglycaemic symptoms. A diagnosis of T2DM was made using a standard oral glucose tolerance test to which patient’s postprandial hypoglycaemia was attributed. He was given dietetic advice for postprandial hypoglycaemia and was followed up routinely. After 2 years, hypoglycaemic symptoms worsened by exercise and delayed meals. A number of supervised fasting glucose measurements failed to demonstrate biochemical hypoglycaemia. His insulin, c-peptide and pro-insulin levels were mildly elevated but plasma glucose levels were normal. A CT scan showed 20 mm lesion in the pancreas which was confirmed as insulinoma with pancreatic arterial calcium stimulation studies. Laparoscopic resection confirmed benign insulinoma and hypoglycaemia resolved. Our case illustrates the importance of considering insulinoma as a cause of postprandial hypoglycaemia.