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Insulinoma

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Insulinoma, Pancreatic Islet Cell Tumor

  • See Also
  1. Fasting Hypoglycemia
  2. Hypoglycemia
  3. Paraneoplastic Syndrome
  • Epidemiology
  1. Incidence: 1 to 32 cases per million person years
  • Pathophysiology
  1. Primary neuroendocrine tumor of the islet cell that secretes Insulin
    1. Associated with unregulated hyperinsulinemia due to excessive Insulin secretion from the islet cells
    2. Sporadic in most cases
      1. Associated with Multiple Endocrine Neoplasia Type 1 (MEN 1) in 6-7%
  2. Extrapancreatic tumors may also cause similar effects as a pareneoplastic syndrome
    1. Non-Islet cell tumors (NICTH) synthesize IGF-2 (or Insulin)
    2. Associated with Lung Cancer (including Mesothelioma), Sarcomas and gastrointestinal tumors
  • Findings
  • Symptoms and Signs
  1. See Hypoglycemia
  2. Fasting Hypoglycemia
  3. Palpitations
  4. Neurologic changes
    1. Tremor
    2. Altered Level of Consciousness (Confusion to coma)
    3. Seizure
  • Diagnosis
  • Lab findings consistent with Insulinoma
  1. Serum Glucose <55 mg/dl
  2. Insulin >=3 uU/ml
  3. C-Peptide >= 0.6 ng/ml
  4. Proinsulin >=5 pmol/L
  5. Beta Hydroxybutyrate <=2.7 mmol/L
  6. Negative Sulfonylurea screen
  • Differential Diagnosis
  1. See Fasting Hypoglycemia
  • Imaging
  1. Localize tumor
    1. CT Abdomen
    2. MRI Abdomen
    3. Endoscopic Ultrasound
  2. Also consider the less common extrapancreatic source if islet tumor not identified
    1. Non-Islet cell tumors or NICTH (Paraneoplastic Syndrome cases
  • Management
  1. See Hypoglycemia
  2. Surgical excision
    1. Most primary islet cell tumors are benign and surgery is curative
  3. Medical Therapy (If surgery delayed or ineffective)
    1. Diazoxide 300-1200 mg/day IV/PO PLUS a Diuretic
    2. Octreotide 150-150 ug/day divided doses SC
  • Resources
  1. Insulinoma (StatPearls)
    1. https://www.ncbi.nlm.nih.gov/books/NBK544299/
  • References
  1. Hofland (2024) J Clin Endocrinol Metab 109(4):1109-18 +PMID: 37925662 [PubMed]
  2. Okabayashi (2013) World J Gastroenterol 19(6):829-37 +PMID: 23430217 [PubMed]