Updated: 12/26/2021

Insulinoma

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  • Snapshot
    • A 54-year old woman presents to her primary care physician complaining of recurrent episodes of diaphoresis, palpitations, and blurry vision. The patient has another episode while in the office. Temperature is 98.6°F (37.0°C), blood pressure is 148/90, pulse is 110/min, and respirations are 20/min. You draw labs at the time, which reveals a serum glucose of 50 mg/dL. Her symptoms are relieved after administration of glucose. A week later, the remainder of the labs come back revealing a high insulin level and high C-peptide.
  • Introduction
    • Overview
      • an insulinoma is a neuroendocrine tumor of the beta cells of the pancreas that results in inappropriate insulin secretion
      • classically presents with the Whipple triad
        • signs and symptoms of hypoglycemia
        • serum glucose < 55 mg/dL
        • reversibility of symptoms upon glucose administration
      • cases are usually benign and are managed surgically
  • Epidemiology
    • Incidence
      • rare, 1-4 cases per 100,000,000 annually
      • most common islet cell tumor
    • Risk factors
      • family history of multiple endocrine neoplasia (MEN) type 1
      • > 50 years of age
      • female
  • ETIOLOGY
    • Pathogenesis
      • mechanism
        • solitary adenoma or hyperplasia of islet cells of the pancreas results in inappropriate production and secretion of insulin
  • Presentation
    • Symptoms
      • hypoglycemic symptoms
        • diaphoresis
        • palpitations
        • headache
        • dizziness
        • confusion
        • change in vision
    • Physical exam
      • tachycardia
      • tremor
  • Imaging
    • Computerized tomography of abdomen
      • indications
        • common first imaging study for the evaluation of insulinoma after a laboratory diagnosis is made
      • findings
        • hyperdense lesion usually located within the pancreas
    • Ultrasonography
      • indications
        • alternative study for the evaluation of insulinoma
    • Magnetic resonance imaging of abdomen
      • indications
        • alternative study for the evaluation of insulinoma
  • Studies
    • Diagnostic approach
      • laboratory evidence of inappropriate insulin secretion establishes a diagnosis of insulinoma and precedes further workup with imaging
      • evaluation under fasting or postprandial conditions may be pursued depending on when the symptoms usually occur
    • Serum labs
      • insulin to glucose ratio > 0.4
      • pro-insulin
      • C-peptide
      • sulfonylurea and meglitnide
  • Differential
    • Factitious hypoglycemia
      • key distinguishing features
        • may arise from inappropriate administration of insulin or other medications that alter insulin secretion (e.g., sulfonylureas)
  • Treatment
    • Surgical
      • resection of tumor
        • indication
          • initial treatment of insulinoma
  • Complications
    • Metastasis to other organs
    • Diabetes
  • Prognosis
    • Most cases are benign adenomas (80-90%) and respond well to treatment

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