C-peptide in serum

Reference values ​​of concentration of C-peptide in serum in adults - 0,78-1,89 ng / ml.

The C-peptide is a fragment of the proinsulin molecule, resulting in the cleavage of which insulin is formed. Insulin and C-peptide are secreted into the blood in equimolar amounts. The half-life of the C-peptide in the blood is higher than that of insulin, so the C-peptide / insulin ratio is 5: 1.Determination of the concentration of C-peptide in the blood allows us to characterize the residual synthetic function of p-cells in patients with diabetes mellitus. C-peptide, unlike insulin, does not cross-react with insulin AT, which allows its level to determine the content of endogenous insulin in patients with diabetes mellitus. Given that the insulin medications do not contain the C-peptide, its determination in the blood serum makes it possible to evaluate the function of the pancreatic p-cells in patients with diabetes who are receiving insulin. In a patient with diabetes mellitus, the value of basal C-peptide level and especially its concentration after loading with glucose( during PTTG) allows to determine the presence of resistance or sensitivity to insulin, to determine the phases of remission and thereby adjust the therapeutic measures. When exacerbation of diabetes, especially type 1, the concentration of C-peptide in the blood decreases, which indicates the insufficiency of endogenous insulin.

In clinical practice, the determination of the C-peptide in the blood is used to establish the cause of the resulting hypoglycemia. In patients with insulinoma, there is a significant increase in the concentration of C-peptide in the blood. To confirm the diagnosis, a test is performed to suppress the formation of the C-peptide. In the morning, the patient is taken blood to determine C-peptides. Then, for 1 hour, insulin is injected intravenously from 0.1 U / kg and blood is taken again. If the C-peptide level decreases less than 50% after insulin administration, it can be assumed with confidence that an insulin secretant tumor exists.

Monitoring the C-peptide content is especially important in patients after the operative treatment of insulinoma, the detection of an elevated C-peptide in the blood indicates a metastasis or a relapse of the tumor.

The main diseases in which the concentration of C-peptide in the blood can vary is shown in the table.

Table Changes in serum C-peptide concentrations for various diseases and conditions

Table Changes in C-peptide concentrations in serum for various diseases and conditions

Increased concentration of	Decreased concentration of
Insulinoma	Introduction of exogenous insulin
CRF	Diabetes mellitus type 1
Diabetes mellitus type 2