insulinom

An insulinoma is a rare pancreatic neuroendocrine tumor that secretes insulin. Most insulinomas are solitary and benign; malignant forms occur less often. They arise from pancreatic beta cells and represent the most common cause of endogenous hyperinsulinemic hypoglycemia. The incidence is about 1–4 per million people per year. Insulinomas can occur sporadically or as part of multiple endocrine neoplasia type 1 (MEN1).

Clinical presentation is dominated by recurrent hypoglycemia due to excessive insulin secretion. Symptoms include neuroglycopenia (confusion, visual changes, seizures) and autonomic signs (tremor, palpitations, sweating). Whipple's triad describes the classic syndrome: hypoglycemic symptoms, low plasma glucose, and relief with glucose. Diagnosis relies on a supervised 72-hour fast showing hypoglycemia with inappropriately elevated insulin, C-peptide, and proinsulin, while sulfonylurea exposure is excluded.

Localization is achieved with imaging such as contrast-enhanced CT or MRI, endoscopic ultrasound, and functional imaging like Ga-68 DOTATATE PET/CT. Intraoperative ultrasound can aid resection. Management is primarily surgical: enucleation for small, benign tumors distant from the main pancreatic duct; segmental or more extensive pancreatic resection for other cases or MEN1-associated disease. Medical therapies include diazoxide to suppress insulin release and somatostatin analogs; everolimus or cytotoxic chemotherapy for metastatic disease.

Prognosis is favorable after complete resection for sporadic benign tumors, with low recurrence. Recurrence and progression are more likely in MEN1-associated insulinomas or malignant cases. Follow-up includes clinical evaluation and periodic testing of glucose, insulin, and C-peptide.