Abstract
We report an elderly patient with insulinoma in whom severe hyperglycemia was induced by octreotide, and who was finally treated with a minimal dose of the agent. An 89-year-old woman found to be hypoglycemic (20 mg/dl) experienced morning faintness. Her plasma insulin was 12 μg/ml and C-peptide 3.3 mg/dl during hypoglycemia. We diagnosed insulinoma as her counter-regulatory hormones responded normally, chromogranin A was markedly elevated, and a tumor was detected at the pancreas head. In consideration of her age and a dissecting aneurysm, we selected octreotide treatment. Upon the administration of 50 μg of octreotide, her plasma glucose rose to 555 mg/dl, which finally recovered 36 hours later. After titration, we found that a dose of 10 μg/day was optimal to control plasma glucose and to avoid hypoglycemic faintness. Octreotide is often used for insulinoma treatment; however, a dose as low as 10 μg/day is unusual. The reaction may have been due to the tumor expression of hypersensitive subtype receptor(s) of somatostatin or its analogs. This mechanism, together with insulin resistance as an adaptation phenomenon against prolonged hyperinsulinemia, could also explain why octreotide, which usually does not induce hyperglycemia in any situation, caused hyperglycemia in this patient.
