‘C’ peptide reflects:
**Core Concept**
The 'C' peptide is a byproduct of insulin degradation and reflects the level of insulin secretion. It is a peptide fragment that remains attached to the insulin molecule during its synthesis and is cleaved off during storage and release.
**Why the Correct Answer is Right**
The 'C' peptide is a reliable indicator of endogenous insulin production, as it is produced in equimolar amounts to insulin. The presence of 'C' peptide in the blood suggests that the insulin is of endogenous origin, whereas the absence of 'C' peptide may indicate exogenous insulin administration. This is particularly useful in diagnosing factitious hypoglycemia or insulinoma.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as the 'C' peptide is not a marker of glucose metabolism or insulin resistance.
**Option B:** Incorrect, as the 'C' peptide is not a byproduct of glucagon degradation.
**Option C:** Incorrect, as the 'C' peptide is not a direct indicator of pancreatic beta-cell function.
**Clinical Pearl / High-Yield Fact**
In patients with suspected insulinoma or factitious hypoglycemia, measuring 'C' peptide levels can help differentiate between endogenous and exogenous insulin production. This is a crucial step in diagnosis and management.
**Correct Answer: C. A byproduct of insulin degradation and reflects the level of insulin secretion.**