RD - Commission on Dietetic Registration (CDR) Practice Test

Which compound is used as a clinical indicator of endogenous insulin production?

1. Glucose

2. C-peptide

3. Glutamic acid

4. Cortisol

The correct answer is: C-peptide

C-peptide is the correct compound used as a clinical indicator of endogenous insulin production. When proinsulin is cleaved into insulin, C-peptide is released as a byproduct. Measuring the levels of C-peptide in the blood provides insight into how much insulin the pancreas is producing. This is particularly important for differentiating between type 1 and type 2 diabetes, as well as assessing insulinoma (a tumor of the pancreas that produces insulin). The other compounds listed do not serve as reliable indicators of endogenous insulin production. Glucose levels can be influenced by various factors, including dietary intake and genetic predispositions, making it less specific for assessing insulin production. Glutamic acid, while important in various metabolic processes, is not directly related to endogenous insulin secretion. Cortisol, a stress hormone, can affect blood sugar levels but is not a direct indicator of insulin production. Thus, C-peptide stands out as the most accurate and clinically relevant marker for measuring endogenous insulin levels.