• Neoplasm of the pancreatic β cells of the islets of Langerhans leading to hyperinsulinemia. Pancreatic β cells manufacture proinsulin, which is then cleaved into insulin and C-peptide before secretion.
  • Most common functional (insulin producing) tumor of the pancreas
  • 90% are located within the pancreas.
  • Usually small with 90% <2 cm; suspect malignant insulinoma if tumor is >4 cm.
  • Symptoms due to hypoglycemia and concomitant cerebral glucose deprivation
  • Diagnosis of insulinoma is often delayed due to vague and unusual presentation of neuroglycopenic symptoms.
  • Hypoglycemic episodes are irregular, recurrent, and tend to increase in frequency and severity over time.
  • Definitive management consists of surgical resection.
  • Synonym(s): β-cell tumor; β-cell adenoma; nesidioblastoma



  • 3 to 4 cases per 1 million person-years
  • 10% malignant, 10% multiple tumors (1)
  • Two major categories: sporadic (>90%) and multiple endocrine neoplasia type 1 (MEN1) syndrome (5–10%); etiology dictates treatment approach (2).
    • Sporadic type tends to be solitary and benign; sporadic type associated with slight female predominance (3)
    • When insulinoma associated with MEN1, usually accompanied by multiple lesions; patients typically present in the 3rd decade of life without significant gender-specific incidence (2).

The prevalence of insulinoma is 0.4% (4).


  • Mutations in DAXX and ATRX have been identified in 43% of pancreatic endocrine tumors (4).
  • MEN syndrome associated with approximately 10% of cases; result of mutation in menin gene on long arm of chromosome 11 (2,5)

Risk Factors

MEN1 syndrome only known risk factor (1)

Commonly Associated Conditions

MEN1 syndrome (1)

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