C- Peptide Test
Patients with diabetes may get a C-peptide test as a means of distinguishing type 1 diabetes from type 2 diabetes or Maturity onset diabetes of the young (MODY). Measuring C-peptide can help to determine how much of their own natural insulin a person is producing as C-peptide is secreted in equimolar amounts to insulin. C-peptide levels are measured instead of insulin levels because C-peptide can assess a person's own insulin secretion even if they receive insulin injections, and because the liver metabolizes a large and variable amount of insulin secreted into the portal vein but does not metabolize C-peptide, meaning blood C-peptide may be a better measure of portal insulin secretion than insulin itself.
C-Peptide Test - Everything You Should Know
C-Peptide is useful in the evaluation of pancreatic beta cell function (e.g., helping distinguish type 1 from type 2 diabetes mellitus, or monitoring patients who have received islet cell or pancreatic transplants) and for determining the source of insulin in patients with hyperinsulinemic hypoglycemia (e.g., distinguishing insulin-secreting tumors from exogenous insulin administration). It is also sometimes measured as an additional means (more resistant to hemolysis than is insulin itself) for evaluating glucose tolerance tests.
C-Peptide is a by-product of insulin. C-Peptide consists of a chain of 31 amino acids and is produced, together with insulin, in the beta cells of the pancreas, by enzymatic cleavage of proinsulin. Insulin and C-Peptide are secreted in equal amounts and released into the circulation through the hepatic portal vein.
C-Peptide plays an important role in the assembly of the two insulin chains. The liver extracts about half of the amount of insulin and only a very small percentage of C-Peptide, so C-Peptide persists in the peripheral circulation in concentrations 5-10 times higher and with lower fluctuations than insulin.
Unlike insulin, C-Peptide is not degraded in the liver, being removed from the circulation by the kidneys, a fraction being excreted as such in the urine. C-Peptide concentrations are elevated in kidney disease.
The overall role of the C-Peptide test is to offer a pragmatic guide and a clinical way to manage individuals that suffer from diabetes.
What C-Peptide Test Measures and Why Should You Care
C-Peptide, insulin, and blood glucose measurements are used in the differential diagnosis of hypoglycemia to ensure proper management and therapy of patients.
Some symptoms of hypoglycemia are:
- Nervousness and anxiety
- Irritability, impatience
- Confusion and delirium
- Accelerated heart rate
- Blurry vision
- Excessive hunger and nausea
- Tingling or numbness of the tongue or lips
- Nightmares or crying crises during sleep
- Loss of consciousness
- Lack of coordination of voluntary movements
- Muscle spasms
Also, measurement of C-Peptide may appreciate endogenous insulin secretion better than insulin levels due to the high prevalence of anti-insulin antibodies.
Moreover, C-Peptide values are also helpful in assessing residual beta-cell function in the early stages of type 1 diabetes and for the differential diagnosis between latent autoimmune diabetes (LADA) in adults and type 2 diabetes.
Elevated C-Peptide levels may result from increased beta-cell activity, seen in:
- Renal failure
A correlation has also been found between elevated C-Peptide levels and hyperlipoproteinemia and hypertension.
Low C-Peptide levels are seen in:
- Hypoinsulinism (a deficient secretion of the insulin by the pancreas)
- Addison's disease
What Should You Know Before Getting Tested?
In order to get the most accurate result, it is recommended to take the test in the morning. The test should be performed before breakfast, and the last meal should be consumed at least eight h before getting tested.
You should also avoid exercising the day before the test, and take a break of 10-20 minutes, and relax in the clinic.
How is the Test Performed?
The test will be performed by a health professional. The method used will be venipuncture. A sterile needle will be inserted in a vein, usually in the forearm, to collect the necessary blood sample.
The blood collection is done in vacutainer without anticoagulant, with/without activating hole, with/without separating gel (vacutainer with red or yellow plug), as far as the vacuum allows. Specimens harvested that show severe hemolysis or that are improperly collected in other types of vacutainers will be rejected from testing.
Among some adverse effects that you may encounter, the most common one would be a small bruise where the needle was inserted. Other more significant issues may be fainting or vomiting. It is recommended to drink water after and stay seated for a little while after.
How are the Values Interpreted?
Patients with insulin-secreting neoplasms have elevated levels of endogenous insulin and C-Peptide. In contrast, patients with hypoglycemia have low C-Peptide levels in the presence of elevated (exogenous) serum insulin levels.
In the case of low glucose tolerance, an increase in C-Peptide during the glucose tolerance test leads to insulin resistance.
Differentiation between type I and type II diabetes is done by the simultaneous determination of glucose and C-Peptide in the oral glucose tolerance test. C-Peptide concentrations are low in type I and normal/high in type II.
Important is the distinction between latent or late autoimmune type I diabetes (LADA), which has low concentrations of specific autoantibodies, and type II diabetes.
What Are the Normal Values for the C-Peptide Test?
Even though laboratories may use different measurement ranges, the generally accepted C- peptide levels lay between 0.5-2.00 (ng/mL). Nevertheless, the results should be interpreted by a doctor also considering your medical history, age, gender, etc.
What Elevated C-Peptide Levels May Indicate?
High C-Peptide levels may indicate that your organism produces too much insulin. This situation is called hyperinsulinemia, and it refers to higher values of insulin among people not suffering from diabetes.
Some disorders that can increase the C-Peptide levels are:
- Insulinomas, commonly known as tumors
- Acute kidney failure
- Cushing syndrome-endocrine disorder
- Insulin resistance (when testing for glucose, an increase in C-Peptide levels may increase because of low tolerance to glucose)
- Type 2 diabetes medication with sulfonylureas like glipizide, glimepiride, glyburide, tolbutamide.
What Low C-Peptide Levels may Indicate?
Lower C-Peptide levels may indicate that your organism is not producing enough insulin. This situation is called hypoinsulinism. Some causes of this include:
- Type 1 or 2 diabetes-usually, type 1 diabetes diagnosed persons usually have an even lower C-Peptide level than type 2 diabetes
- Inefficient pancreas functioning or pancreas removing
- Fasting for prolonged periods
- Exogenous insulin injection
Clinical Uses of the C- Peptide Test
- Patients with diabetes may have their C-peptide test levels measured as a means of distinguishing type 1 diabetes from type 2 diabetes or Maturity onset diabetes of the young (MODY). Measuring C-peptide can help to determine how much of their own natural insulin a person is producing as C-peptide is secreted in equimolar amounts to insulin. C-peptide levels are measured instead of insulin levels because C-peptide can assess a person's own insulin secretion even if they receive insulin injections, and because the liver metabolizes a large and variable amount of insulin secreted into the portal vein but does not metabolize C-peptide, meaning blood C-peptide may be a better measure of portal insulin secretion than insulin itself. A very low C-peptide confirms Type 1 diabetes and insulin dependence and is associated with high glucose variability, hyperglycemia and increased complications. The test may be less helpful close to diagnosis, particularly where a patient is overweight and insulin resistant, as levels close to diagnosis in Type 1 diabetes may be high and overlap with those seen in type 2 diabetes.
- Differential diagnosis of hypoglycemia. The test may be used to help determine the cause of hypoglycemia (low glucose), values will be low if a person has taken an overdose of insulin but not suppressed if hypoglycemia is due to an insulinoma or sulphonylureas.
- Factitious (or factitial) hypoglycemia may occur secondary to the surreptitious use of insulin. Measuring C-peptide levels will help differentiate a healthy patient from a diabetic one.
- C-peptide may be used for determining the possibility of gastrinomas associated with Multiple Endocrine Neoplasm syndromes (MEN 1). Since a significant number of gastrinomas are associated with MEN involving other hormone producing organs (pancreas, parathyroids, and pituitary), higher levels of C-peptide together with the presence of a gastrinoma suggest that organs besides the stomach may harbor neoplasms.
- C-peptide levels may be checked in women with Polycystic Ovarian Syndrome (PCOS) to help determine degree of insulin resistance.
Limits and Interference
- C-Peptide levels are elevated in patients with chronic renal failure.
- In the assessment of hypoglycemia, determination of insulin and C-Peptide is not useful if serum glucose is greater than 60 mg / dL.
May cause interference with some components of the kit and result in the following inconclusive results:
High dose biotin treatment (> 5 mg/day); therefore, it is recommended that blood be collected at least 8 hours after the last administration;
- Very high titers of anti-streptavidin and anti-ruthenium antibodies.
Order your C-Peptide Test Now
Health is a gift, and we should all make efforts to maintain it at its best. The C-Peptide blood is a very important tool, especially for diabetics. It can determine under any circumstance how much insulin a diabetic can produce naturally and thus, keep it under control. Most problems can be solved if identified quickly. For more reliable information and support, go to DiscountedLabs.com and choose the closest lab to your home through an easy process.
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