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Zorluk: ZorEndocrinology and Metabolism

A clinician is evaluating four non-diabetic adult patients who presented with recurrent episodes of neuroglycopenia. A 72-hour fasting test was performed for each patient. Match each patient's laboratory profile obtained during the symptomatic hypoglycemic episode (glucose <55 mg/dL<55\text{ mg/dL}) to the most likely underlying etiology.

  • Glucose 35 mg/dL35\text{ mg/dL}; Insulin 18 \muU/mL18\text{ \mu U/mL} (High); C-peptide 2.5 ng/mL2.5\text{ ng/mL} (High); Elevated proinsulin; Negative secretagogue screen.Insulinoma (pancreatic neuroendocrine tumor)
  • Glucose 40 mg/dL40\text{ mg/dL}; Insulin 22 \muU/mL22\text{ \mu U/mL} (High); C-peptide 0.05 ng/mL0.05\text{ ng/mL} (Low); Suppressed proinsulin; Negative secretagogue screen.Factitious exogenous insulin administration
  • Glucose 38 mg/dL38\text{ mg/dL}; Insulin 15 \muU/mL15\text{ \mu U/mL} (High); C-peptide 2.8 ng/mL2.8\text{ ng/mL} (High); Normal proinsulin; Positive sulfonylurea screen.Unintentional or factitious secretagogue ingestion
  • Glucose 32 mg/dL32\text{ mg/dL}; Insulin 1 \muU/mL1\text{ \mu U/mL} (Low); C-peptide 0.04 ng/mL0.04\text{ ng/mL} (Low); Suppressed proinsulin; Elevated IGF-II to IGF-I ratio.Non-islet cell tumor hypoglycemia (NICTH)

Cevap

Profile 1 matches Insulinoma; Profile 2 matches Exogenous insulin; Profile 3 matches Secretagogue ingestion; Profile 4 matches Non-islet cell tumor hypoglycemia.
Each patient's hypoglycemia etiology is systematically determined by evaluating the presence of endogenous insulin production (C-peptide), precursor processing (proinsulin), and exogenous secretagogues.

Adım Adım Çözüm

1
Evaluate serum insulin levels during the hypoglycemic episode.
Profiles 1, 2, and 3 show high insulin (insulin-mediated). Profile 4 shows low insulin (non-insulin-mediated).
This differentiates hyperinsulinemic states from causes like severe liver failure, adrenal insufficiency, or NICTH where insulin is appropriately suppressed.
2
Analyze C-peptide levels in the hyperinsulinemic profiles.
Profile 1 and 3 have high C-peptide. Profile 2 has low C-peptide.
C-peptide is co-secreted with endogenous insulin. High insulin with low C-peptide proves the insulin came from an exogenous source.
3
Check the secretagogue screen and proinsulin levels for profiles with high C-peptide.
Profile 1 has a negative screen and high proinsulin. Profile 3 has a positive screen.
This step distinguishes between autonomous tumoral secretion of insulin (insulinoma) and pharmacologically stimulated endogenous secretion (sulfonylureas/meglitinides).

Anahtar Kavram

Diagnostic evaluation of fasting hypoglycemia using the insulin, C-peptide, and oral hypoglycemic agent screen axis.
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Konular

Endocrinology and Metabolism

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