Glucose-responsive and octreotide-sensitive insulinoma

Lesson of the month 2: An unusual presentation of hyperinsulinaemic hypoglycaemia with possible underlying diagnosis of glucose-sensitive insulinoma or islet cell hyperplasia

Postprandial hypoglycaemia can occur in islet cell hyperplasia and in reactive hypoglycaemia. Less commonly, it can occur with insulinoma. A case is described where the differential diagnosis was glucose-sensitive insulinoma or islet cell hyperplasia. Typical provocation was prolonged exertion or fasting followed by ingestion of sugary snacks resulting in hypoglycaemic seizures and collapse. Biochemistry and computerised tomography imaging were consistent with an insulinoma in the pancreatic tail, but this was not confirmed on endoscopic ultrasound. Selective intra-arterial calcium stimulation with hepatic venous sampling results suggested a diagnosis of islet cell hyperplasia. Ten years later, repeat imaging was consistent with a neuroendocrine tumour. Surgical resection has resulted in remission of symptoms. The patient will be monitored long term to ensure no recurrence.

Glucose-responsive insulinoma in a patient with postprandial hypoglycemia in the morning

We report the case of an obese 79-year-old woman who experienced postprandial hypoglycemia in the morning. The serum immunoreactive insulin (IRI) and C-peptide levels responded in parallel with her serum glucose level during a 75-g oral glucose tolerance test. A prolonged fast test lowered her serum glucose level to 30 mg/dL, but serum IRI was not fully suppressed. Abdominal computed tomography revealed a tumor in the uncinate process of the pancreas. The tumor was histologically diagnosed as benign insulinoma after surgery. Therefore, glucose-responsive insulinoma as well as reactive hypoglycemia should be considered in patients who exhibit postprandial hypoglycemia.

Short- and long-term somatostatin analogue treatment in patients with hypoglycaemia related to endogenous hyperinsulinism

BACKGROUND

The long-term efficacy of somatostatin analogues on insulinomas has not been studied.

DESIGN

A prospective study to evaluate the response of octreotide in 21 patients with hypoglycaemia related to endogenous hyperinsulinism who were not treated by surgery.

RESULTS

Reasons for not undergoing surgery were: refusal (n = 3), old age with multiple diseases (n = 5), unlocalized insulinomas (n = 2), malignant unresectable insulinomas (n = 5), multiple insulinomas (n = 3) and diffuse beta-cell disease (n = 3). Hypoglycaemia was responsive to octreotide in 14 of the 21 patients. A short 100-microg octreotide test correctly predicted the efficacy of treatment in six patients with benign insulinomas. Octreoscan scintigraphy was positive in 6 of the 16 patients of whom three were responsive and three unresponsive to octreotide. Octreoscan scintigraphy was negative in 10 of the 16 patients, eight of whom were responsive to octreotide. Subcutaneous octreotide treatment was prolonged for > 6 months (7-144 months, 67 +/- 47 months) in 11 responsive patients. No tachyphylaxis was observed. However, the octreotide dose had to be increased in two patients after 3 and 18 months, respectively. Only one patient suffered from symptomatic biliary lithiasis after 3 years of treatment.

CONCLUSION

Long-term octreotide treatment can be used to control hypoglycaemia in patients with endogenous hyperinsulinism who are not eligible for surgery; octreotide efficacy on hypoglycaemia could be predicted by a short 100 microg-octreotide test in patients with benign insulinomas, but was not correctly predicted by Octreoscan scintigraphy.