We report here the case of an 83-year-old man who was treated for unconsciousness and hypoglycemia (39 mg/dL) accompanied by marked elevation of serum immunoreactive insulin (IRI) (4,760 μIU/mL). We diagnosed his condition as insulin autoimmune syndrome (IAS, Hirata disease) because of a high insulin autoantibody (IAA) titer (>90%: bound/total) and no history of exogenous insulin administration. Reactive hypoglycemia occurred due to immediate association followed by dissociation between insulin and insulin autoantibodies after glucose or food intake. An α-glucosidase inhibitor in combination with frequent small meals reduced the postprandial hyperglycemia (glucose spike) and ameliorated the reactive hypoglycemia.

Congenital portal systemic encephalopathy without liver cirrhosis and/or portal hypertension is rare. An 86-year-old man with senile dementia was admitted due to disturbance of consciousness. His serum ammonia level was high, but there was no evidence of liver cirrhosis or portal hypertension on laboratory tests and upper abdominal enhanced computed tomography (CT). However, on lower abdominal enhanced CT, a meso-caval shunt was found in the right lower abdomen. Superior mesenteric arteriography revealed a shunt flowing into the inferior vena cava via the right gonadal vein. The shunt was closed by balloon occluded retrograde transvenous obliteration, and dementia-like symptoms improved.

Objective The measurement of C-peptide immunoreactivity (CPR) is essential for evaluating the pancreatic β-cell function and selecting appropriate therapeutic agents in patients with diabetes mellitus. The meal tolerance test (MTT) is simple to administer physiological insulin-stimulating test. Previous studies have reported that several CPR-related indices are useful markers for predicting insulin requirement in type 2 diabetes. In the present study, we investigated the serum CPR response during the MTT in hospitalized patients with type 2 diabetes mellitus in order to clarify the clinical utility of the MTT. Methods We performed the MTT using a test meal with timed measurements of the serum CPR level based on the oral glucose tolerance test over 180 minutes and tested the correlation of various CPR-related indices and clinical factors in patients with type 2 diabetes mellitus. Patients The subjects were patients with type 2 diabetes mellitus who had been admitted to our hospital for diabetes management and education. The final study population consisted of 68 patients. Results The fasting CPR level was correlated with the 24-hour urinary CPR excretion and body mass index. The serum CPR level at 120 minutes in the MTT was strongly correlated with the area under the curve of CPR during the MTT. The patients who needed insulin therapy at 6 months after hospitalization showed a significant lower incremental CPR value from 0 to 120 minutes in the MTT than those who did not need insulin therapy. Conclusion The plasma C-peptide levels at 0 and 120 minutes in the MTT provide essential information for the clinical management of patients with type 2 diabetes mellitus.