Endocrine Abstracts

Section 1: Case history: Persistent hyperinsulinemic hypoglycaemia may be caused by either a solitary tumour of the pancreas secreting excessive insulin, i.e. an insulinoma or, rarely by nesidioblastosis. A 70-year-old man was referred with symptoms of hypoglycemia. He had a positive 72-hour-fast with episodes of hypoglycemia and high insulin levels.

Section 2: Investigations: EUS showed a small 3 x 4mm hyperechoic lesion in the body of the pancreas. His Octreotide scan and calcium stimulation test failed to locate any other discreet lesions. He was started on trial of Diazoxide and somatostatin analogue but didn’t tolerate them due to GI side effects. Routine genetic screening for causes of congenital hyperinsulinism did not identify a pathogenic variant.

Section 3: Results and treatment: Following NET MDT, he had a laparotomy and underwent a distal pancreatectomy for the treatment of suspected insulinoma. The histopathology showed a 3mm well differentiated NET grade 1, consistent with an Insulinoma. Mitotic activity was 1 per 20 HPF and the Ki67 was <2%. The remaining pancreas showed focal prominent islets and ductuloinsular complexes. On screening, 3 other family members had positive 72-hour-fasts. They all had octreotide scans, MRI Pancreas and 68Ga-DOTA-exendin-4 PET/CT localisation scans, that reported no insulinoma. Following NET MDT, they all had either distal or subtotal pancreatectomies. Their symptoms have now improved but not fully resolved. The histopathology on these patients revealed 3 of 4 major criteria and 1 of 4 minor criteria for a histopathological diagnosis of diffuse adult nesidioblastosis.

Section 4: Conclusions and points for discussion: We describe a unique case series of a family who presented with symptoms of hyperinsulinemic hypoglycemia. Insulin mediated hypoglycemia can be difficult to characterise and the source difficult to localise. However, when no discrete abnormality is found, other diagnoses should be considered. In our family, an insulinoma was found in only one of the patients while findings consistent with neisidioblastosis, were found in the others. Whole genome sequencing is ongoing on affected family members.