Endocrine Abstracts

Introduction: Insulinomas are rare neuroendocrine tumours that cause excessive insulin secretion and lead to hypoglycemia. Diagnosing these tumours can be challenging, with around 20% of patients initially misdiagnosed with neurological or psychiatric disorders. Moreover, locating the tumour is often difficult. This report discusses a 33-year-old man who experienced neuroglycopenic episodes for a year before being diagnosed with an insulinoma, highlighting the localization challenges faced in his case.

Case Report: A 33-year-old male with no significant medical history was referred for evaluation of non-diabetic hypoglycaemia on April 12, 2024, due to symptoms of light-headedness, confusion upon waking, fatigue, irritability, and difficulty concentrating that began in July 2023. Observations indicated that his symptoms improved with food intake, prompting the couple to purchase a glucose monitor, which recorded readings as low as 1.9 mmol/L. Following a reluctant admission to the hospital on April 21, 2024, he underwent a 72-hour fast revealing a plasma glucose level of 2.2 mmol/L, elevated insulin and C-peptide levels, while tests for sulphonylurea were negative, indicating probable insulinoma. Dietary interventions were initially attempted, but due to recurrent hypoglycaemia, the patient was prescribed diazoxide. Subsequent imaging investigations, including CT and MRI, failed to locate the tumour, leading to a referral for a 68 Ga-Dota-Tate-PET-CT which also yielded no results. However, an endoscopic ultrasound on July 24, 2024, identified a subtle 13.1 x 4.8 mm isoechoic lesion in the pancreas, which upon biopsy confirmed a grade 2 neuroendocrine tumour. Post-biopsy, the frequency of hypoglycaemic episodes decreased, and the patient was successfully weaned off diazoxide. He was subsequently referred for endoscopic ultrasound and enucleation of the tumour.

Conclusion: Insulinomas can present diagnostic and management challenges and smaller tumours can be difficult to locate. Our case outlines the importance of pursuing investigations and the utility of endoscopic ultrasound in tumour localization.