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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(M2.OMB.1) A 44-year-old nurse presents to the emergency department with confusion. This has happened to her several times this past month with increasing frequency. Each time, her symptoms improved with eating, but the episodes continue to recur. She is otherwise healthy. She lives with her mother who has diabetes whose medications include metformin, insulin, lisinopril, amlodipine, and glyburide. Her temperature is 98.0°F (36.7°C), blood pressure is 132/81 mmHg, pulse is 85/min, respirations are 16/min, and oxygen saturation is 98% on room air. Physical exam reveals a confused woman. She is moving all her extremities but follows commands poorly. Laboratory studies are ordered as seen below.

Hemoglobin: 14 g/dL
Hematocrit: 41%
Leukocyte count: 7,500/mm^3 with normal differential
Platelet count: 199,000/mm^3

Serum:
Na+: 140 mEq/L
Cl-: 102 mEq/L
K+: 4.0 mEq/L
HCO3-: 23 mEq/L
BUN: 30 mg/dL
Glucose: 29 mg/dL
Creatinine: 1.4 mg/dL
Ca2+: 10.2 mg/dL
Sulfonylurea level: undetectable
C-peptide level: 55 ng/mL (normal < 5 ng/mL)

Which of the following is the most likely etiology of this patient’s symptoms?

QID: 216610

Alpha cell tumor

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Beta cell destruction

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Beta cell tumor

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Insulin overdose

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Sulfonylurea overdose

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M 10

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