Endocrine Abstracts

Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycemia and characterized with autoantibodies to insulin in a patient without prior exposure to exogenous insulin. Medications with sulfydryl group and autoimmune diseases are known to be associated with this syndrome. Nearly 90% of the cases were reported in Japanese patients. We presented a Turkish patient with insülin autoimmune syndrome possibly caused by α-lipoic acid. A 62-year-old woman was admitted to our clinic recurrent episodes of sweating, weariness, heart palpitations and anxiety occurring both fasting and postprandial. The first episode was two weeks before admission and the capillary glucose was measured as 40 mg/dl during episode. She had been diagnosed with hypertension and hyperlipidemia for ten years and treated with indapamid, nebivolol and atorvastatin. She had never been diagnosed as diabetes mellitus and never injected insulin before. She had no family history of diabetes or autoimmune disease. She had been taken multivitamin preparation which contained α-lipoic acid until three weeks prior to her hospitalization. Laboratory investigations revealed normal renal and liver functions. During hypoglycemic event, serum glucose was 46 mg/dl; serum insulin was 1890 μIU/ml (normal: 1.9-23) and C-peptide was 11.9 ng/mL (normal value 0.9–7.1). Proinsulin levels was 33.8 pmol/l (normal: <8). An oral glucose tolerance test showed hypoglycemia with inappropriately high insulin levels at 300 min. The 72-h fasting test, abdominal computed tomography (CT) and magnetic resonance imaging (MRI) were normal. Insulin recovery was 6.6% after polyethylene glycol precipitation. No interference was detected with heterophile blocking tubes. Insulin antibodies was measured as 79% (normal: <8.2) and the patient was diagnosed as insulin autoimmune syndrome. Patient was instructed not to use the suspected medication again. Diet with low carbonhydrate and frequent small meals was planned. Her symptoms resolved and no hypoglycemic event was recorded. Insulin levels have decreased from 1890 μIU/ml to 76 μIU/ml (normal: 1.9-23) during follow-up. In all hyperinsulinemic hypoglycemic cases, especially in patients taking medications known to be associated with the syndrome and having very high insulin levels, the diagnosis of insülin autoimmun syndrome should be kept in mind.