Endocrine Abstracts

Insulinomas are neuro-endocrine tumours of the pancreas with an incidence of 0.7-4 cases per 1,000,000 population per year. Type 1 diabetes has an incidence of >20 cases per 100,000 per population per year. Cases of insulinoma with diabetes are lower than in the general population with a type 2 preponderance. This report is the seventh of insulinoma with type 1 diabetes suggesting the latter inhibits the development of the former. A 31 year old female with a 20 year history of type 1 diabetes presented with increased frequency and severity of hypoglycaemic episodes over 6 months. For 1 month daily pre-breakfast hypoglycaemic episodes had occurred despite nocturnal consumption of carbohydrate and withdrawal of insulin. The nature of the hypoglycaemic episodes and Covid restrictions necessitated a day case investigation protocol commencing non-fasted at 09:00 hours. Basal investigations confirmed glucose 3.9 mmol/l, insulin 19.6 mU/l, proinsulin 48 pmol/l, c-peptide 1097 pmol/l and cortisol 270 nmol/l. At 2 hours glucose 2.3 mmol/l, insulin 15.2 mU/l, proinsulin 51 pmol/l, c-peptide 1161 pmol/l and cortisol 528 nmol/l coincidental with neuroglycopenic and autonomic nervous system symptoms. IV dextrose corrected the hypoglycaemia with resolution of symptoms fulfilling Whipple’s triad. CT imaging confirmed a 2.5 cm diameter head of pancreas mass. Treatment with diazoxide, prednisolone and octreotide was ineffective and a hypoglycaemic seizure necessitated urgent surgical intervention in the form of pylorus sparing pancreaticoduodenectomy. Insulin treatment was necessary post-surgery. Histology confirmed a well differentiated neuro-endocrine tumour grade 1 (Ki 67 index 1%). C-peptide was <50 pmol/l. The development of insulinomas in beta cell deplete type 1 diabetes remains an enigma. Benign and malignant insulinomas have occurred in the 7 cases now described suggesting the cells of both escape the immune processes that affected normal beta cells.