A 53 year old male nurse presents with drowsiness and confusion for several hours. Prior to becoming drowsy, he complained of palpitations and sweating. He was previously well, with an unremarkable medical history. He does not drink or use recreational drugs. His full blood count and electrolytes are normal, but his capillary blood sugar is 40 mg/dl. Following administration of IV dextrose, he recovers completely.
The sulfonylurea screen is negative
The patient becomes symptomatic after 16 hours of fasting. Investigations show: RBS: 39 mg/dl (low) S. Insulin: 16 uU/ml (high) S. C-peptide: 2.9 ng/ml (high) No ketone bodies
No antibodies to insulin or insulin receptors are detected
The contrast CT scan of the abdomen shows an enhancing lesion in the pancreatic body which is 1.1cm in diameter. No other abnormalities are noted.