What are the diagnostic guidelines for insulinoma?

Updated: May 31, 2020
  • Author: Zonera Ashraf Ali, MBBS; Chief Editor: Neetu Radhakrishnan, MD  more...
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Answer

For the evaluation of insulinoma, National Comprehensive Cancer Network guidelines recommend abdominal multiphasic CT or MRI and measurement of serum insulin, pro-insulin, and C-peptide levels during concurrent hypoglycemia. The following studies may also be performed, as appropriate [39] :

  • Endoscopic ultrasound (EUS)
  • Other biochemical evaluation as clinically indicated 
  • Somatostatin receptor–based imaging;  68Ga-dotatate imaging preferred (PET/CT or PET/MRI) or somatostatin receptor scintigraphy
  • Chest CT ± contrast
  • Consider testing for inherited genetic syndromes

European Neuroendocrine Tumor Society guidelines note that "the exact criteria for the diagnosis of insulinoma continue to evolve and vary in different consensus documents and reviews", but cite proposed diagnostic criteria from a consensus report from the US Endocrine Society, which include endogenous hyperinsulinism documented by symptoms, signs, or both, and plasma findings as follows [61] :

  • Glucose < 55 mg/dl (3.0 mmol/L)
  • Insulin ≥3.0 μU/ml (18 pmol/L)
  • C-peptide ≥0.6 ng/ml (0.2 nmol/L)
  • Proinsulin ≥5.0 pmol/L

Evaluation of serum chromogranin A (CgA) levels are frequently not helpful for diagnosing insulinoma, as an elevated CgA value has only a 73% specificity, compared with 92% specificity for non-insulinoma pancreatic NETs. [61]


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