Insulinoma

Insulinoma

 

Insulinomas are functional islet cell neoplasms which may be associated with Multiple Endocrine Neoplasias type 1 (MEN 1).

Epidemiology

  • Incidence – 1-3/million yearly
  • Age – median age of onset is 40-50 years
  • Sex – slightly higher incidence in females
  • Occurrence – sporadic most of the time

Risk Factors

  • Genetic – around 10% associated with the MEN 1 Syndrome

Pathophysiology

  • Insulinomas
    • 5-10% are malignant – tend to be associated with familial disease
    • Most common functioning endocrine tumor of the pancreas
    • Second most common functioning pancreatic tumor in MEN 1 syndrome
  • Diffuse islet cell hyperplasia, adenomas and carcinomas are typically present
  • Islet cells can develop into macroadenomas, microadenomas or malignant adenocarcinomas
    • Frequently multiple tumors are present
  • Cause of symptoms is excess hormonal secretion of insulin

Clinical Presentation

  • Hypoglycemia, confusion, headache, sweating, tremor
  • Other manifestations associated with MEN 1 tumors may occur
    • Pituitary, pancreatic and parathyroid tumors

Diagnosis

  • Laboratory testing
    • Fasting blood sugar ≤45 mg/dL, serum insulin >6 µIU/mL and/or proinsulin levels ≥5 pmol/L when glucose is ≤45 mg/dL, C-peptide levels ≥0.6 ng/mL
    • Urine/serum sulfonylurea screen to rule out factitious hypoglycemia
  • Imaging studies
    • CT/MRI
  • Histological studies
    • Final confirmation of tumor type – special stains may be required

Differential Diagnosis

  • Diabetes mellitus
  • Hypoglycemia from other causes including factitious
  • Factitious use of sulfonylureas or insulin
  • Nesidioblastoses

See Also