The diagnosis and management of hyperinsulinaemic hypoglycaemia

Abstract

Hyperinsulinaemic hypoglycaemia (HH) is an uncommon but important differential to consider in patients without diabetes mellitus (DM) presenting with abnormal neurological and autonomic symptoms. Insulinomas are the most common cause of HH in adults. However, insulinomas themselves are rare and are therefore often missed. We herein report on a 72-year-old non-diabetic Pākehā male with an insulinoma, presenting with recurrent bouts of hypoglycemia and syncope. Imaging revealed a lesion in the pancreatic head, which was successfully medicated and resected soon after. This case demonstrates the appropriate diagnostic evaluation and management of patients with HH, particularly for those with insulinomas. Due to its rarity, HH remains a confusing clinical presentation in patients without DM and can prove to be a diagnostic challenge for many clinicians. CaseA 72-year-old non-diabetic Pākehā male presented to Middlemore Hospital following an episode of transient confusion and hypoglycaemia. The patient had eaten lunch at 1200, and spent the afternoon building outside, before sitting down for a rest at 1530. The next thing the patient remembers is being in an ambulance. His family reported difficulty rousing him from his chair and that he "appeared drunk" with slurred words and an unsteady gait. The patient's capillary blood glucose level recorded in the ambulance at 1550 was 2.6mmol/L; his symptoms promptly resolved following glucose administration. There was no history of urinary or faecal incontinence, tongue biting, or limb jerking. No known fever, chest pain, shortness of breath, palpitations, headache, limb weakness or loss of sensation. The patient reported no history of early morning sweats, fainting, nausea, or unintentional weight loss.The patient had previously been admitted twice for two similar episodes in October 2019 and November 2020. Both times he presented with similar symptoms in the setting of hypoglycaemia (<2.8mmol/L), both of which resolved following glucose administration. The patient also reported experiencing two brief episodes of confusion, light-headedness and diplopia over the last two months, which resolved after eating food. He does not monitor his blood sugar levels at home.His past medical history includes osteoporosis and osteoarthritis, for which he takes Risedronate sodium 35mg PO once weekly and paracetamol 1g PO QID PRN, respectively. He also has benign prostatic hyperplasia, for which he takes Terazosin 5mg PO OD. There is no personal or family history of type 1 or type 2 diabetes mellitus (DM). The patient has no access to any diabetic medications. His family history is significant for a malignant pancreatic neuroendocrine tumour (pNET), Ki-67 8.6%, pT2N1 with lymphatic spread, for which his sister recently underwent surgical resection. No genetic testing has been performed. The patient is independent with mobilisation and with all activities of daily living, except driving. He has no allergies, has never smoked, and drinks ~1 beer per week. PHYSICAL EXAMINATIONThe patient was ale...