Abstract
A 73-year-old female was admitted to our hospital in a coma in December 2011. The laboratory analyses upon admission revealed hypoglycemia, with a serum glucose level of 29 mg/dl and a serum immunoreactive insulin level of 23.3 μIU/ml, which rapidly improved after glucose injections. Abdominal computed tomography (CT) demonstrated a large tumor (6×10×12 cm) in the body and tail region of the pancreas. Distal pancreatectomy was performed in February 2012. The histological diagnosis was a low grade (G1) neuroendocrine tumor (NET), made on the basis of the current WHO classification. Immunohistochemically, the tumor cells were positive for insulin and chromogranin A. After the operation, the serum C-peptide and urinary C-peptide levels decreased from 7.3 to 1.6 ng/ml and from 51.8 to 10.1 μg/day, respectively. The HOMA-β was 27.3 %and the CPR index was 0.8. Hyperglycemia persisted after surgery because of the decreased endogenous insulin. Therefore, insulin therapy was initiated. The present case suggests that a large insulinoma in the body and tail region of the pancreas can cause a significant decrease in endogenous insulin and a postoperative requirement for insulin therapy.
