C-Peptide Suppression

C-Peptide Suppression

Rationale: This test has been used in cases in which the 72-hour diagnostic fast is inconclusive.1,2 Production of C-peptide by normal subjects is generally suppressed during hypoglycemia. The degree of C-peptide suppression is diminished in patients with insulinoma. Normative data, based on age and body mass index (BMI), are calculated as weight (kg) divided by the square of height in meters.2 The extent of suppression (as a percentage) of the 60-minute C-peptide concentration relative to the baseline sample should be ≥ the values tabulated as follows.

 

Age (y)

BMI (kg/m2)

20-24

25-29

30-34

20-29

67%

66%

65%

30-39

65%

64%

62%

40-49

63%

61%

59%

50-59

61%

59%

57%

60-69

59%

57%

54%

70-79

57%

54%

51%

Protocol: After an overnight fast, insulin (0.125 units/kg) should be infused over a period of 60 minutes. Blood should be collected for glucose and C-peptide measurements at baseline and 60 minutes.2

Orderable Tests: 143302 C-Peptide x2 (baseline, one-hour)

Note: Intravenous access should be maintained, and glucose should be available for infusion.

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