Endocrine Abstracts

Insulin autoimmune syndrome is a rare cause of spontaneous hypoglycemia caused by insulin antibodies directed against endogenous insulin. A woman in her 70s presented with subacute onset of recurrent episodes of fasting and postprandial hypoglycemia fulfilling Whipple’s triad with no weight gain. There was no history of gastric bypass surgery. Initially, insulinoma was considered. During spontaneous hypoglycemia of 2.4 mmol/l, insulin and C-peptide levels were markedly elevated with a negative sulfonylurea screen ruling out exogenous insulin administration and factitious hypoglycemia. A 72-hour supervised fast and mixed meal test showed early-onset hypoglycemia with high insulin and C-peptide levels. Imaging including MRI and DOTATATE PET-CT revealed no evidence of neuroendocrine tumors. Insulin IgG antibodies were found to be significantly high. Considering rarity of condition, MDT decided to repeat supervised fast and PEG precipitation showed insulin antibodies interference confirming diagnosis of insulin autoimmune syndrome.