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Soru

Zorluk: OrtaEndocrinology and Metabolism

Match each of the following fasting laboratory profiles, obtained during a symptomatic hypoglycemic episode, to the most likely underlying etiology. Assume normal renal and hepatic function.

  • InsulinomaLow glucose, elevated serum insulin, elevated C-peptide, and a negative oral hypoglycemic agent screen
  • Surreptitious exogenous insulin administrationLow glucose, elevated serum insulin, low/suppressed C-peptide, and a negative oral hypoglycemic agent screen
  • Sulfonylurea or meglitinide ingestionLow glucose, elevated serum insulin, elevated C-peptide, and a positive oral hypoglycemic agent screen
  • Non-islet cell tumor hypoglycemia (NICTH)Low glucose, low/suppressed serum insulin, low/suppressed C-peptide, and elevated IGF-II

Cevap

The correct pairings differentiate the etiologies of hypoglycemia based on the relationship between insulin, C-peptide, and secretagogue screens. Insulinomas and sulfonylureas show high C-peptide (distinguished by the drug screen), exogenous insulin shows low C-peptide despite high insulin, and non-islet cell tumors show suppression of both.
Each etiology of hypoglycemia has a distinct biochemical signature. Endogenous hyperinsulinemia (insulinoma and sulfonylurea) elevates C-peptide, requiring a drug screen to separate the two. Exogenous insulin causes hyperinsulinemia without C-peptide elevation. Non-islet tumors suppress both.

Adım Adım Çözüm

1
Analyze insulin and C-peptide levels simultaneously during the hypoglycemic episode.
Determines if the hyperinsulinemia is from an endogenous or exogenous source.
Endogenous insulin is always co-secreted in equimolar amounts with C-peptide. Exogenous insulin administration causes hyperinsulinemia but lacks C-peptide, and the resulting hypoglycemia suppresses endogenous production.
2
Evaluate the oral hypoglycemic agent screen if both insulin and C-peptide are elevated.
Differentiates an autonomous insulin-secreting tumor (insulinoma) from drug-induced endogenous secretion (sulfonylurea).
Both conditions cause endogenous hyperinsulinemia, making toxicological screening the only definitive way to distinguish them biochemically.
3
Assess for IGF-II or other extrapancreatic causes if both insulin and C-peptide are suppressed during severe hypoglycemia.
Identifies non-islet cell tumor hypoglycemia (NICTH).
Tumor-produced IGF-II activates insulin receptors directly, causing profound hypoglycemia which then appropriately suppresses the endogenous HPA and pancreatic hormone axes.

Anahtar Kavram

Differentiation of adult hypoglycemia utilizing fasting laboratory profiles of insulin, C-peptide, and toxicological screens.
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Konular

Endocrinology and Metabolism

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