Endocrine Abstracts

The localization of biochemically proven insulinoma remains a challenge despite the advent of more sensitive methods for radiological detection. We report a case with conflicting cross-sectional, angiographic and scintigraphic findings, in which selective angiography combined with intra-arterial calcium stimulation and hepatic venous sampling (ASVS) proved to be the most accurate localizing investigation.

A 17-year-old female with cerebral palsy and learning difficulty, but no prior endocrinopathy, presented with a 6-month history of seizures typically occurring prior to breakfast. She was admitted to hospital for a 72-hour fast, but developed symptomatic hypoglycaemia almost immediately, with biochemical profiling confirming the diagnosis of insulinoma [plasma glucose 1.9 mmol/l, insulin 67 pmol/l (NR 0–60), proinsulin 131 pmol/l (NR 0–7), 32–33 split proinsulin 100 pmol/l (NR 0–13), sulphonylurea screen negative]. Serum corrected calcium (2.3 mmol/l, NR 2.1–2.5) and prolactin (142 mU/l, NR 59–619) levels were normal. High dose diazoxide therapy and a continuous 10% dextrose infusion were required to maintain euglycaemia pre-operatively. CT of the abdomen demonstrated a bulky pancreatic head, but failed to reveal a discrete mass. Two small lesions were also identified within the liver, with appearances suggestive of possible metastases. Endoscopic ultrasound by an experienced radiologist confirmed an enlarged/lobulated pancreatic head, but no other abnormality. Whole body octreotide scintigraphy failed to demonstrate any abnormal uptake. Selective angiography with ASVS revealed a tumour blush and insulin secretory response only in relation to the splenic artery, suggesting functional tumour within the pancreatic body/tail.

At operation, direct visualization and palpation of the pancreas, coupled with intra-operative ultrasound, identified a 11 mm mass within the body. The head of the pancreas was normal. Frozen section biopsy of the liver lesions revealed focal nodular hyperplasia. Accordingly, surgical resection was limited to a distal pancreatectomy. Histology confirmed the presence of a single insulinoma. The patient has suffered no further hypoglycaemic episodes post-operatively.