Concurrent insulinoma and impaired glucose tolerance suspected as owing to obesity

Abstract

An obese 68-year-old woman was admitted for examination of fasting hypoglycaemia. A prolonged 18 h fast reduced her plasma glucose without suppressing insulin secretion, while plasma β-hydroxybutyrate levels were suppressed. Despite the prolonged fast, the glucose response to glucagon was increased by 25 mg/dL (1.39 mM) glucose, which is compatible with insulinoma. A 75 g oral glucose tolerance test (75 g OGTT) showed impaired glucose tolerance. An abdominal CT scan revealed a mass lesion in the uncinate process of the pancreas, a finding consistent with the results of angiography and selective artery calcium injection test. The patient then underwent a pancreaticoduodenectomy; the pancreatic mass was histologically diagnosed as benign insulinoma. After surgery, a prolonged 24 h fast caused no hypoglycaemia and the glucose tolerance capacity in 75 g OGTT improved. Eight months after surgery, the patient's body weight had reduced by 10 kg. This is therefore a case of concurrent insulinoma and impaired glucose tolerance.

Impaired glucose tolerance with neurological manifestations in insulinoma

“…Few reports have established the relation between insulinoma and glucose intolerance and/or diabetes. 9 , 10 , 11 …”

“…Few reports have established the relation between insulinoma and glucose intolerance and/or diabetes. [9][10][11] Insulin to C-peptide ratio is used to distinguish between hypoglycemia caused by exogenous insulin and that caused by insulinoma, because C-peptide only forms when endogenous insulin is activated. With exception of patients receiving exogenous insulin and patients with liver cirrhosis, insulin to C-peptide ratio in a normal healthy living person never exceeds 1.0.…”