Endocrine Abstracts

Insulinomas are rare, functional neuroendocrine tumours (NETs) that secrete excessive insulin. They are often diagnosed late due to their variable presentation and rarity. While predominantly solitary and benign, a minority of insulinomas can present as malignant. Insulinomas typically carry a hallmark clinical presentation characterised by Whipple’s triad; symptoms of hypoglycaemia (e.g., sweating, palpitations, headaches, confusion), documented low blood glucose levels and resolution of symptoms following glucose administration. However, this is not a specific syndrome and the intersection of NETs and insulinomas further contribute to deviation between textbook and real-world presentation. Furthermore, even with a multitude of imaging modalities, localisation is not always possible in some cases, further complicating management. The following cases explore four patients initially diagnosed with non-functional or mixed-hormone secreting NETs, who later developed hypoglycaemic episodes, and were eventually diagnosed with insulinomas. In each case, patients first presented with non-specific symptoms typical of NETs, such as abdominal pain, flushing, or diarrhoea. These symptoms dominated the clinical picture, overshadowing early signs of hypoglycaemia. For example, Patient A, initially diagnosed with a well-differentiated NET of the pancreas, had reported sweating and dizziness at presentation, signs only later attributed to an insulinoma-induced hypoglycaemia. Similarly, Patient B experienced hypoglycaemic episodes months before his neuroendocrine tumour diagnosis, which were overlooked, culminating in a severe hypoglycaemic episode leading to a road traffic accident over two years later. Patient C experienced low blood sugars years after his initial diagnosis. Patient D had longstanding episodic fatigue and dizziness, initially dismissed until home readings revealed frequent low glucose episodes, leading to his insulinoma diagnosis. These cases highlight the diagnostic complexity of NETs and, more specifically, insulinomas. Consistently, hypoglycaemia in patients with neuroendocrine tumours is often late-presenting, missed or considered a secondary issue until it becomes severe or recurrent. The complexity of NET symptoms, combined with the overshadowing presence of primary tumour-related manifestation, contributes to delayed diagnosis. Clinicians must remain vigilant for hypoglycaemia in NET patients, as early detection and treatment of insulinomas can improve overall mortality and morbidity, namely complications of recurrent hypoglycaemia, including long-term neurological sequelae and critical incidents, such as motor vehicle collisions.