Introduction: Symptomatic hypoglycaemia unrelated to the treatment of diabetes is rare. As symptoms of hypoglycaemia are non-specific, investigation should only be instigated if Whipples triad can be fulfilled- signs and symptoms of hypoglycaemia, a recorded low plasma glucose and resolution of symptoms after treatment.
Case history: A 37 year-old woman presented to the emergency department with fatigue and lightheadedness. She has modified her diet to alleviate her symptoms and gained over a stone. She has a daughter and family history of Type 1 and Type 2 diabetes but has no access to diabetes medications or insulin. She has no family history of Multiple Endocrine Neoplasia (MEN). Blood glucose recorded during admission was 1.6 mmol/l. After treatment, her symptoms resolved rapidly. Two fasting samples of glucose done by her own GP were 3.6 mmol/l and 1.8 mmol/l. Further investigations showed early morning cortisol of 465 nmol/l, calcium 2.71 mmol/l (2.22.6), parathyroid hormone of 13.2 pmol/l (1.36.85), IGF-1 48.9 nmol/l (1437), normal prolactin and thyroid function. She was admitted for a 72-h fast and developed hypoglycaemia just after 12 h with blood glucose of 2.1 mmol/l. Insulin and c-peptide at the time were inappropriately elevated, 3.3 mu/l (<3) and 0.36 nmol/l (<0.2) respectively. Although insulin was only mildly elevated, proinsulin was markedly elevated at 72 pmol/l (<5). Serum sulfonylurea screen and insulin antibodies were negative. CT scan revealed well-defined low attenuation lesion in the superior aspect of the head of pancreas measuring 5×3 cm and incidental left adrenal adenoma. MRI pancreas showed multi-focal pancreatic lesion and PET scan showed metabolically active pancreatic lesion with no metastases. Further testing showed negative urinary metadrenalines, elevated chromogranin A 71 pmol/l (059) and chromogranin B 173 pmol/l (0149) which is consistent with neuroendocrine tumour. She has multiple conditions compatible with a diagnosis of MEN-1 and genetic testing for MEN-1 was positive. She is currently awaiting total pancreatectomy and further work up of her primary hyperparathyroidism and pituitary imaging will be required.
Discussion: An insulinoma is the commonest endogenous cause of hyperinsulinaemic hypoglycaemia and second most common pancreatic islet cell tumour associated with MEN-1. Patients with insulinoma should receive counselling for potential lifelong requirement for insulin after pancreatectomy. MEN-1 is autosomal dominant with high penetrance and the finding of this mutation has implications on the patient and family members who will require screening for associated tumours.
16 - 18 Apr 2018
Society for Endocrinology