Endocrine Abstracts

A 58-year-old non-diabetic Caucasian man was admitted with a capillary glucose of 1.9 mmol/l following an episode of confusion and disorientation. During his admission he had frequent episodes of nocturnal and early morning hypoglycaemia with capillary glucose <3.0 mmol/l. After 21 h of supervised fasting he was symptomatic with plasma glucose 2.3 mmol/l, insulin >1000 mU/l and C-peptide 19.6 μg/l. Sulphonylurea screen was negative. Given the magnitude of serum insulin, insulin antibodies were measured and were positive. Serum insulin was corrected for the presence of antibodies using PEG precipitation yet remained elevated.

CT imaging of pancreas was normal. Endoscopic ultrasound demonstrated a hyper-echoic abnormality in the tail of the pancreas measuring 13×11 mm. He subsequently attended for calcium stimulated venous sampling which demonstrated high insulin production throughout the gland with no localisation. The patient started carbohydrate supplementation and 5 mg daily prednisolone with resolution of hypoglycaemia over 8 weeks.

Insulin autoimmune hypoglycaemia is a rare condition characterised by extremely high levels of insulin in the presence of anti-insulin antibodies. It is the third leading cause of hypoglycemia in Japan but has rarely been described in the non-Asian population. Making the correct diagnosis is important to avoid an unnecessary pancreatic surgical procedure on a hypoglycemic patient.