C- peptide is secreted by –
**Core Concept**
C-peptide is a peptide hormone that is secreted by the pancreas, serving as a marker for endogenous insulin production. It is co-secreted with insulin from the beta cells of the islets of Langerhans in the pancreas. The measurement of C-peptide levels is used to assess pancreatic insulin secretion and reserve.
**Why the Correct Answer is Right**
C-peptide is secreted by the beta cells of the pancreas, which are responsible for producing and secreting insulin. The synthesis of insulin involves the precursor molecule proinsulin, which is split into insulin and C-peptide during processing. As a result, the ratio of insulin to C-peptide is typically constant, making C-peptide a reliable marker for endogenous insulin production. The co-secretion of C-peptide and insulin is a key aspect of normal pancreatic function.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because C-peptide is not secreted by the alpha cells of the pancreas, which primarily produce glucagon.
**Option B:** This option is incorrect because C-peptide is not secreted by the delta cells of the pancreas, which produce somatostatin.
**Option C:** This option is incorrect because C-peptide is not secreted by the pancreatic polypeptide-producing cells, which produce pancreatic polypeptide.
**Clinical Pearl / High-Yield Fact**
C-peptide levels are often measured in conjunction with insulin levels to assess pancreatic reserve and insulin production. A low C-peptide-to-insulin ratio may indicate exogenous insulin use or insulin resistance.
**Correct Answer: D. The pancreas. C-peptide is secreted by the pancreas.**