Endocrine Abstracts

Introduction: Apart from occurring sporadically, insulinoma within the framework of multiple endocrine neoplasia 1 (MEN-1) is well known. The rare presence of multifocal insulinomas has recently been assigned a separate entity (insulinomatosis). The difficulty of localising insulinomas may be improved by GLP1-receptor imaging.

Case report A 48-year-old woman had been treated for suspected epileptic seizures for 2 years (lamotrigine). During another such episode low blood glucose (BG) was detected. During fasting she was unaware of hypoglycaemia (BG 2.3 mmol/l), endogenous hyperinsulinism was established. With a history of treated prolactinoma (operation, quinagolid) – and slightly elevated calcium levels MEN-1 was considered. ⁶⁸Ga-DOTA-Exendin-4 PET/CT and MRI revealed a major lesion located directly left to the pancreatic head (8×13 mm) and smaller lesions in the tail (max. 5 mm). After pretreatment with diazoxid/prednisolone surgery was proposed. Intraoperatively, granular pancreatic tissue was palpated mainly located in the left side up to the head of the pancreas – matching with the increased uptake in GLP-1R imaging. As intraoperative ultrasound did not confirm a focal lesion, left-sided pancreatectomy was performed. Histologically the major lesion proved to be insulin-positive, however 37 more small adenoma, mainly with insulin staining were detected establishing the diagnosis of insulinomatosis. The postoperative course was complicated by a peripancreatic abscess and recurrence of asymptomatic mildly low BG levels. Genetic testing (MEN-1) is pending.

Conclusions: i) GLP-R imaging is useful in benign insulinomas and might be useful in the context of MEN-1 in order to separate insulin secreting neuroendocrine tumours (NET) from other secreting and non-secreting NETs, ii) GLP-1R imaging showed positive lesions in the case of insulinomatosis. However, most of the lesions were too small to be detected by ⁶⁸Ga-DOTA-Exendin-4 PET/CT. iii) Clinical and biochemical work-up of this patient suggests that insulinomatosis occurred in the context of MEN-1 that – if confirmed – would be a new association.