Unspecific clinical manifestations of insulinoma found in preoperative testing: a case report and narrative review.

Background: Insulinoma is a rare endocrine tumor that is clinically characterized by the Whipple's triad and can be part of multiple endocrine neoplasia syndrome type 1 (MEN1). Most insulinomas are less than 2 cm, but the smaller the tumor diameter, the lower the imaging sensitivity. Here we present a case of recurrent asymptomatic hypoglycemia with unremarkable contrast-enhanced CT and MRI imaging that led to the delayed identification of an insulinoma. The tumor was localized with the invasive selective arterial calcium stimulation test (SACST). Case presentation: A 59-year-old female presented with asymptomatic hypoglycemia detected in preoperative screening on two occasions over the past year. She had no classic symptoms of hypoglycemia such as dizziness, weakness, blackouts, anxiety, palpitations, tremors, or profuse sweating. Detailed history taking revealed that she has had two episodes of sudden irritability, personality changes, and abnormal violent behavior that were relieved with food. After extensive endocrine hormone testing and imaging to exclude the possibility of MEN1, she was diagnosed with a 1.5-cm insulinoma in the pancreatic tail. Her blood glucose, insulin and C-peptide levels returned to normal after tumor excision. Conclusion: Hypoglycemia unawareness develops after recurring episodes of hypoglycemia and increases the risk of life-threatening hypoglycemia. This case highlights the importance of identifying the underlying cause of hypoglycemia and implementing timely intervention.