Endocrine Abstracts

Insulinomas are rare neuroendocrine tumours with an estimated incidence of up to four new cases per mill./p.a. Most tumours are benign, <2 cm and arise from the islets of Langerhans.

Typically patients present with Whipple’s triad: symptoms of hypoglycaemia, caused by fasting or exercise, low plasma glucose and symptoms relieved by Food. The diagnosis is confirmed by high insulin and c-peptide levels, inappropriately high for prevailing glucose.

Here we report a case of an insulinoma which presented initially with recurrent unexplained episodes of confusion and disorientation. No medical advice was sought until he presented with Severe hypoglycaemia with a plasma glucose of 1.6 mmol/l. Subsequent investigations showed that he became promptly hypoglycaemic during OGTT.

During a 72 h fast, the patient became hypoglycaemic after 16 h. High levels of C-peptide and insulin were evident. The pancreatic CT-scan showed a 2 cm mass in the uncinate process which was of higher attenuation in both arterial and PV phase. The octreotide scan showed uptake in the corresponding area as seen on the CT. Initial treatment with octreotide given subcutaneously was started and ameliorated his recurrent hypoglycaemia. He subsequently underwent successful laparoscopic enucleation of the insulinoma. The patient remains asymptomatic but follow-up CT-scans are indicated as histological findings showed adverse prognostic features with tumour cell nests and vascular and peri-neural invasion.

This is an unusual presentation in that no fasting hypoglycaemia was reported and most episodes were late in the postprandial phase. This case reports shows that the diagnosis of insulinoma can often be delayed due to lack of classic presentation. They can also be falsely attributed to psychiatric or neurological disorders. Not seeking medical advice could potentially be fatal. We suggest that patients with history of postprandial hypoglycaemia in the absence of dumping syndrome should be investigated with a prolonged fast to rule out insulinoma.