Investigation Result (reference range) Plasma insulin* >100 (0-16) Plasma C-peptide* 2617 (140-1390) Chromogranin A 156 (0-56) Gut hormones**, short synacthen test, liver, bone and renal profiles Within reference range CA 199 and CEA Within reference range Ultrasound and CT abdomen 2.5cm diameter low density lesion in head of pancreas; isolated 2cm hypodense lesion in right lobe of liver *plasma glucose 1.8 mmol/l; ** gastrin, glucagon, pancreatic polypeptide, somatostatin, vasoactive intestinal polypeptide

Table 2: Inappropriately elevated serum insulin and C peptide levels during significant hypoglycaemia and chromogranin A levels suggested an insulin secreting pancreatic neuroendocrine tumour, which was confirmed by CT scanning of the abdomen.