What is with the peptide in the analysis. Analysis for C-peptide (how to take it and why it is needed)

06.05.2020

C peptide is an integral part of the analysis to determine the glycemic index in the blood in patients of various ages. The sampling is carried out in two stages: first, blood is taken from a vein, and then the sampling is repeated a couple of hours after eating glucose. According to the results laboratory research diagnose diabetes 1 or 2 types. Modern methods research virtually eliminates errors in laboratory diagnostics diabetes mellitus.

Graphical representation of c-peptides

Features of c-peptides

C peptide - what is it? C-peptide (literally "connecting peptide") is a clear indicator of the body's production of natural internal insulin. C-peptide is a complex protein compound that characterizes the work of pancreatic beta cells and the production of proinsulin. It is secreted by the pancreas along with endogenous insulin. With a certain biochemical interaction, the protein is cleaved into c-peptide and insulin. The linking peptide level is considered to be a marker of natural insulin. Thus, when this protein compound is found in the blood, the production of endogenous insulin occurs naturally, and the level of c-peptide shows how much insulin is produced.

The initial basis of the protein is preproinsulin, which consists of 110 amino acids. All of them are connected by A-peptide, L-peptide, B-peptide and C-peptide. L-peptide, separating in an insignificant proportion from preproinsulin, cuts off the connection of the C-peptide and binds the A and B groups. Insulin is simultaneously released into the blood with the c-peptide in the same volume, which makes it possible to record the amount of insulin in the blood by the level of the protein compound. Despite the total amount of volume released into the blood, the level in the blood of both components differs. Such differences are due to the rate of "life" of the components in the blood. So, insulin lives for about 4 minutes, and c-peptide for 18-20 minutes. The speed of life fully affects the concentration of c-peptide in the blood, which is almost 5 times higher than the concentration of insulin.

Purpose of analysis

The C index of the peptide, the norm and deviation of which are determined only after the study of blood tests, is one of the methods differential diagnosis. A laboratory study of c-peptide and insulin is prescribed to patients by an endocrinologist to exclude or confirm diabetes mellitus of the non-insulin-dependent or insulin-dependent type. Insulin in the human body is of paramount importance, but despite this, the appointment of an analysis for the content of active insulin is not always carried out due to low efficiency. After the production of insulin, it penetrates into the hepatic structures, where its first absorption takes place. After that, insulin enters the general circulation.

Typical blood sugar measurement

Often analyzes for a reason complex mechanisms transportation of insulin through the body show low levels of the hormone. Modern diagnostic methods make it possible to practically reliably determine the amount of insulin in the blood. Analysis is assigned under the following conditions:

liver disease of any origin;
polycystic ovaries;
suspicion of the development of insulinoma;
determination of the effectiveness of insulin therapy;
obesity, sudden weight gains;
feeling of constant thirst;
increase in the volume of daily diuresis;
somatotropin (pituitary adenoma).

Important! The C-peptide does not reflect the amount of glucose that enters the body with food, unlike the analysis for insulin, therefore, excess amounts of sugar will not be displayed in the analyzes. Analysis of the content of the c-peptide is an affordable way to assess the production of your own insulin.

Order of conduct

Analysis for c peptide requires some preparation from the patient, which will determine the final results. The average fasting interval before the test is 5-8 hours. The bigger, the better. In some cases, the doctor may reduce or increase the required interval for evaluating other indicators to determine the optimal replacement therapy. Sometimes a complete cancellation may be necessary. medications. The analysis involves compliance with the following algorithm:

organization of venous access (release of the area of the cubital vein, application of a tourniquet above the intended insertion zone, antiseptic of the proposed injection site of the needle or catheter);
venous puncture;
taking blood into a test tube (the test tube may be empty or contain a special gel);
applying a pressure bandage to prevent hematoma.

A test tube with biological material is subjected to centrifugation, plasma is separated, which is frozen to a temperature of 18-20 degrees.

C-peptides in a graphic image

Important! The sampling is carried out in the morning. After passing the analysis, the patient can begin their usual life. Preparation for the analysis of children and adults is no different.

Normal performance

With the peptide, the norm in women is the same along with men, it is a constant stable value. Thanks to laboratory parameters, the doctor can reliably assess the condition of the pancreas, diagnose malignant or benign tumors that can produce insulin. The analysis can be ordered gynecological pathologies, with burdened nephrological history. The rate of c-peptide is the same in adult patients of any gender. Normal performance in children are determined individually, based on many parameters. The norm indicators vary in the range of 0.8-7.2 ng / ml. The dynamics of the increase in the level of c-peptide in the blood corresponds to a similar movement of insulin. The fasting rate varies from 0.76 to 1.87 ng / ml. In children, the indicators of the protein compound on an empty stomach can reach the lower limit of the norm. If other studies deny the development of any pathologies, then a slight deviation from the norm is allowed. Insulinoma differs from actual hypoglycemia by the ratio of the volume of insulin and c-peptide.

Increasing the indicator

If the peptide is elevated, what does it mean? With an increase in the level of protein in the blood is equal to or slightly less than unity. This indicates an increased production of the internal hormone insulin. If the values are above 1.0, then there is an additional dose of insulin in the blood. The main reasons for increasing the level of the connecting peptide include:

hypertrophic changes in the islets of Langerhans;
overweight, including all stages of obesity;
insulinoma;
type 2 diabetic disease;
cancer of the head of the pancreas.

In addition, long QT syndrome, sulfonylurea drugs, estrogens, or sugar-lowering drugs can affect the increase in protein levels.

Decrease in indicators

It is indicative that the substance may be below normal in the syndrome of alcoholic hypoglycemia, as well as in type 1 diabetes mellitus. Also, the peptide is lowered as a result of active insulin therapy, but in this case, a decrease in indicators is considered the norm.

Important! Sometimes there are cases of peptide levels beyond the norm or closer to normal when taking an analysis on an empty stomach. These indicators indicate the impossibility to establish the type of diabetic disease. To fully determine the rate of the peptide for a particular patient, a stimulated test is used (more often, injections of glucagon, which is an antagonist of the insulin hormone), are used.

C-peptide is a complex protein that characterizes the state of the pancreas. Timely delivery of the analysis eliminates the risks of developing diabetes in individuals with predisposing factors. A feature of laboratory research is the correct preparation of the patient for a blood test for c peptide. Simultaneous intravenous administration hormone with a peptide for type 2 diabetics helps to avoid complications of diabetes: nephrotic syndrome, angiopathy or polyneuropathy.

The junction peptide (C-peptide) is the portion of the proinsulin peptide chain that is cleaved off to form insulin. Insulin and C-peptide are end products of the transformation of proinsulin in β-cells of the pancreatic islets (PZ) as a result of the action of endoleptidase. In this case, insulin and C-peptide are released into the bloodstream in equimolar amounts.

The plasma half-life of C-peptide is longer than that of insulin: C-peptide is 20 minutes, insulin is 4 minutes. It is because of this that C-peptide is present in the blood approximately 5 times more than insulin, and therefore the C-peptide / insulin ratio is 5:1. This suggests that C-peptide is a more stable marker compared to insulin. Insulin is removed from the circulation system by the liver, and C-peptide is removed by the kidneys. The detection of C-peptide concentration in the blood makes it possible to characterize the residual synthetic function of β-cells (after stimulation with glucagon or tolbutamide), in particular in patients treated with heterogeneous insulin. IN practical medicine C-peptide detection is used to elucidate the causative factor of hypoglycemia. For example, in patients with insulinoma, a significant increase in the concentration of C-peptide in the blood is detected. To confirm the diagnosis, a C-peptide genesis suppression test is performed. In the morning, blood is taken from the patient to detect C-peptide, after which insulin is administered intravenously for one hour at the rate of 0.1 U/kg, and blood is again taken for analysis. If the level of C-peptide after insulin infusion falls by less than 50%, one can definitely assume that the patient has an insulin-secreting tumor. Analysis of the C-peptide allows you to evaluate the secretion of insulin against the background of the use of exogenous insulin, in the presence of autoantibodies to insulin.

C-peptide, unlike insulin, does not form a cross-link with insulin antibodies (AT), which makes it possible to determine the content of endogenous insulin in diabetic patients by its level. Knowing that medical preparations insulin does not contain C-peptide in its composition, its level in blood serum can be used to assess the function of pancreatic β-cells in patients with diabetes mellitus who are on insulin treatment.

How is the procedure?

Blood sampling for C-peptide analysis is carried out from the cubital vein on an empty stomach. The last meal should be at least 8 hours before the study. Avoid drinking alcohol 24 hours before the test and stop smoking one hour before.

Indications for the appointment of a blood test for C-peptide

differential diagnosis of type 1 and type 2 diabetes mellitus;
choice of tactics for the treatment of diabetes mellitus;
assessment of the residual function of β-cells in patients with diabetes on the background of insulin therapy;
detection and control of remission of juvenile diabetes mellitus;
diabetes in obese adolescents;
predicting the course of diabetes mellitus;
diagnosis of insulinoma;
suspicion of artificial hypoglycemia;
assessment of the probability of fetal pathology in pregnant women with diabetes mellitus;
assessment of insulin secretion in liver diseases;
control after pancreatic resection.

Analysis result interpretation

Increasing concentration:

insulinoma;
metastasis or recurrence of insulinoma;
hypertrophy of β-cells;
AT to insulin;
non-insulin-dependent diabetes mellitus type 2;
hypoglycemia while taking oral hypoglycemic drugs of sulfonylurea derivatives;
somatotropinoma;
apudoma;
food intake;
reception medicines(estrogens, progesterone, glucocorticoids, chloroquine, danazol, oral contraceptives);
type 2 diabetes mellitus;
polycystic ovary syndrome.

Decrease in concentration:

administration of exogenous insulin;
type 1 diabetes mellitus;
type 2 diabetes mellitus (except early stage);
insulin-dependent type 1 diabetes;
alcoholic hypoglycemia;
stressful state;
AT to insulin receptors in insulin resistant type 2 diabetes mellitus;
radical operation on the pancreas.

Norms

Norm: 0.78-1.89 ng / ml (SI: 0.26-0.63 mmol / l).

C-peptide (from the English connecting peptide, can be translated as "connecting peptide") - a substance that is formed when proinsulin is cleaved by peptidases, is an indicator of the secretion of its own insulin. It is curious that the oligopeptide itself, unlike insulin, does not have any effect on blood sugar levels, but it is extremely important for people with diabetes: it has already been proven that complications begin due to its lack.

C-peptide in the blood

Depending on the level of glucose in the blood, preproinsulin is produced in the beta cells of the pancreas. After cleavage from a small branch of the oligopeptide, it turns into proinsulin. With an increase in glucose levels, proinsulin molecules break down into a C-peptide (an oligopeptide 31 amino acids long) and insulin itself. They are both released into the bloodstream. After secretion, insulin and C-peptide through the portal vein are first in the liver, where about 50% of insulin is destroyed. C-peptide is more stable - it is metabolized in the kidneys. The half-life of insulin in the peripheral blood is 4 minutes, and the C-peptide is about 20. Thus, the level of this substance characterizes the production of insulin in the cells of the islets of Langerhans much better than insulin itself.

Diagnostics

Due to the fact that the C-peptide appears in the blood in the same molar mass like insulin, it can be used as a marker for insulin secretion. So, for example, with DM 1 and on late stages DM 2 its concentration in the blood decreases. At an early stage (before the manifesto) DM 2 - increases, and with insulinoma (pancreatic tumors) - the concentration of this substance in the blood is significantly increased. Let's consider this question in more detail.

An increased level is observed when:

insulin-dependent diabetes mellitus,

kidney failure,

the use of hormonal drugs,

insulinoma,

beta cell hypertrophy.

The reduced level is typical for:

insulin-dependent diabetes mellitus in hypoglycemic conditions,

stressful conditions.

Analysis Features

The analysis is carried out:

To indirectly determine the amount of insulin with inactivating antibodies that change the performance, making them smaller. It is also used for severe disorders of the liver.

To determine the type of diabetes mellitus and the characteristics of pancreatic beta cells to select a treatment strategy.

To detect tumor metastases of the pancreas after its surgical removal.

A blood test is prescribed for the following diseases:

Type 1 diabetes, in which protein levels are low;

Type 2 diabetes mellitus, in which the indicators are higher than normal;

The state of postoperative elimination of cancer in the pancreas;

Infertility and its cause - polycystic ovaries;

Gestational diabetes mellitus (the potential risk for the child is specified);

A variety of disorders in the deformation of the pancreas;

Somatotropinoma;

Cushing's syndrome.

In addition, this analysis allows you to identify the cause of the hypoglycemic state in diabetes. This indicator increases with insulinoma, the use of synthetic hypoglycemic drugs.

The level is lowered, as a rule, after taking a large number alcohol or against the background of the introduction of exogenous insulin on an ongoing basis.

The study is assigned if a person complains:

for constant thirst

increase in urine output,

weight gain.

If the diagnosis of "diabetes mellitus" has already been made, then the analysis is carried out to assess the quality of treatment. Incorrectly selected treatment is fraught with complications: most often in this case, people complain of blurred vision and reduced sensitivity of the legs. In addition, there may be signs incorrect operation kidneys and arterial hypertension.

Venous blood is taken for analysis. For eight hours before the examination, the patient should not eat, but you can drink water.

It is advisable not to smoke for at least 3 hours before the procedure and not to be exposed to heavy physical activity and don't be nervous. The result of the analysis can be known already after 3 hours.

C-peptide norm and interpretation

The C-peptide norm is the same in adult women and men. The norm does not depend on the age of patients and is 0.9 - 7.1 ng / ml.

As a rule, the dynamics of the peptide corresponds to the dynamics of the insulin concentration. The fasting norm is 0.78-1.89 ng/ml (SI: 0.26-0.63 mmol/l).

The norms for children in each case are determined by the doctor, since the level of this substance in a child, when analyzed on an empty stomach, may be slightly below the lower limit of the norm, since a fragment of the proinsulin molecule leaves the beta cells into the blood only after eating.

C-peptide is elevated when:

cell hypertrophy of the islets of Langerhans. The islets of Langerhans are areas of the pancreas where insulin is synthesized.
obesity
insulinoma,
type 2 diabetes,
long QT syndrome,
the use of sulfonylurea drugs.
In addition to the above, the C-peptide can be increased when taking certain types of hypoglycemic agents and estrogens.

C-peptide is lowered when:

alcoholic hypoglycemia,
diabetes mellitus type 1.

However, it often happens that the level of the peptide in the blood on an empty stomach is normal, or close to normal. In this case, it is impossible to determine what type of DM a person has. In such situations, it is recommended to conduct a special stimulated test so that the individual norm for a particular patient becomes known.

This research can be done with:

Injections of glucagon (an insulin antagonist), it is strictly contraindicated in people with hypertension or pheochromocytoma,

Glucose tolerance test.

It is optimal to pass both indicators: both an analysis on an empty stomach and a stimulated test. Now different laboratories use different kits to determine the level of a substance, and the norm is somewhat different.

Peptide and diabetes

Modern medicine believes that it is more convenient to control insulin with C-peptide. With the help of the study, it is easy to distinguish endogenous (produced by the body) insulin from exogenous insulin. Unlike insulin, the oligopeptide does not react to insulin antibodies and is not destroyed by these antibodies.

Because the medicines insulin does not contain this substance, then its concentration in the patient's blood makes it possible to assess the work of beta cells. Recall that the beta cells of the pancreas produce endogenous insulin.

In a person with diabetes mellitus, the basal level of the peptide, and in particular its concentrations after glucose loading, makes it possible to understand whether there is insulin resistance. In addition, phases of remission are determined, which allows you to correctly adjust the therapy.

Taking into account all these factors, it can be concluded that the analysis for this substance allows you to evaluate the secretion of insulin in various cases.

People with diabetes who have antibodies to insulin can sometimes have a false elevated level C-peptide due to antibodies that cross-react with proinsulin.

Of particular importance should be given to changes in the concentration of this substance in humans after surgery for insulinoma. A high level indicates either a recurrent tumor or metastases.

Please note: in case of violation of the liver or kidneys, the ratio of oligopeptide and insulin in the blood may change.

Research is needed for:

Diagnosis of the form of diabetes mellitus,

The choice of types of medical therapy,

Choice of type of medicine and dosage,

Determining the level of deficiency of beta cells,

Diagnosis of a hypoglycemic state,

estimates of insulin production,

Definitions of insulin resistance,

Condition control after removal of the pancreas.

For a long time it was believed that the substance itself does not have any special functions, so it is only important that its level is normal. After many years of research and hundreds of scientific papers, it became known that this complex protein compound has a pronounced clinical effect:

With nephropathy,
With neuropathy,
With diabetic angiopathy.

However, scientists have not yet been able to figure out exactly how the protective mechanisms of this substance work. This topic remains open. There is still no scientific explanation for this phenomenon, however, as well as information about side effects C-peptide and the risks that its use may entail. Moreover, Russian and Western doctors have not yet come to a consensus on whether the use of this substance is justified in other complications of diabetes.

01.03.2018

For diabetic patients, not only the level of insulin is important, but also the level of C-peptide. C-peptides what is it and what is the norm in the blood? The literal meaning of this expression is "connecting peptide". By the level of this element, one can judge the causes of a decrease in blood sugar, evaluate how hormone therapy affects insulin synthesis.

What is a c-peptide (cepeptide)?

The pancreas produces the hormone proinsulin, which contains c-peptide. As sugar levels rise, proinsulin breaks down into c-peptide and insulin itself. Both of them enter the blood in equal proportions, that is, the level of c-peptide in the blood measures the rate of insulin synthesis and its amount.

The lifespan of c-peptide in the blood is 20 minutes, and that of insulin is 5 times less. This explains the difference in the content of these substances in the patient's blood, the normal ratio is 1:5.

c-peptide analysis

To determine the level of c-peptide, a venous blood test is prescribed. This study is necessary for all diabetics and patients suffering from pancreatic diseases.

Why take an analysis for c-peptide? The main objectives of the study:

Determination of the volume of insulin cells, if there are antibodies to them.
Accurate diagnosis of diabetes to determine the tactics of further therapy.
Detection of neoplasms in the pancreas.
Clarification of the cause of a sharp decrease in glucose levels (hypoglycemia).

Indications for analysis are:

Specify the type of diabetes.
Infertility in women.
Frequent recurrence of episodes of hypoglycemia.
Evaluation of the functionality of the pancreas after surgery for organ resection.
Evaluation of the effectiveness of insulin therapy.
Suspicion of insulinoma (tumor of the pancreas).
Cushing's syndrome.
Evaluation of the possibility of discontinuation of insulin therapy.
Gestational diabetes mellitus in pregnancy (to assess risks to the fetus).
Monitoring the state of remission in juvenile diabetes.
Patient's complaints about unreasonable weight gain, increased daily diuresis, increased thirst.

The study is carried out using two methods. According to one of them, blood is taken on an empty stomach, the other involves additional stimulation with glucose. The stimulation test is indicated when the c-peptide level is within the normal range in a diabetic patient on an empty stomach. In this case, it is impossible to determine what type of diabetes he has. It is possible to differentiate the form of the disease after conducting a study with a carbohydrate load.

When a person has diabetes, C-peptide tests can often be done during the examination and to make the correct diagnosis. With the help of such a test, you can find out the cause of the manifestation of the pathology, find out the amount of insulin in the blood, determine the quality of the work of beta cells, and also assess the state of the pancreas. Such a test is often used to diagnose other diseases.

C-peptide is a component of insulin. If such an element is removed, then pure insulin can be obtained.

C-peptide controls the production of insulin, which makes it possible to control the work of beta cells located in the pancreas. In its structure, such an element is similar to regular insulin.

A substance can be formed in the process of synthesis, which occurs in the pancreas, when the level of glucose in the blood rises. Such a process is possible with the additional action of endoleptidase, which is an enzyme. When released, these products enter the bloodstream.

Period of existence

The lifespan of the peptide after it enters the bloodstream is longer than that of conventional insulin. Based on the studies, scientists were able to find out that insulin can live in the blood for 3-4 minutes, and C-peptide for 15-20 minutes. Their concentration also depends on the duration of existence of these elements in the blood.

The peptide may not always be present in the blood. It can be removed during the work of the kidneys. The liver is responsible for its excretion in the body.

Thanks to the ability to determine the amount of peptides in the blood, you can find out the level of insulin in it, as well as determine the possibility of complications in pathology. Therefore, doctors recommend such examinations to be carried out regularly. This applies to both children and adults. Testing can help reduce the risk of developing diabetes.

The amount of peptides in the blood

The norm of the peptide in the blood is the same for both women and men. But sometimes there may be an increase or decrease in the norm from the peptide. What does this mean and what are the reasons? This means that certain changes have occurred in the work of the pancreas that require the intervention of doctors.

It is also worth noting that the indicator of the level of the substance does not depend on age. Today, different clinics can base their therapy on different meanings peptide in the blood. Therefore, the norms of this indicator in different hospitals may differ.

Indicators

In children, the amount of peptides in the blood may fluctuate. Therefore, the doctor usually needs to determine the norm of the peptide on his own in this or that case. Also in diabetes, the indicator of the number of peptides is determined by the doctor individually, depending on the complexity of the course of the pathology.

It was found that the amount of elements in the bloodstream depends on various factors. The indicators may be different for those people who took tests on an empty stomach or after eating. Moreover, the sweeter the food, the higher level peptides will be revealed.

In patients with diabetes, the number of peptides can also be different. Despite the fact that such indicators can be defined as conditional, nevertheless, they are taken into account when making a diagnosis and are taken into account when deciphering the test. With an increased concentration of a substance in the blood, doctors should reduce this level.

The value of the peptide and its changes

It is known that C peptide may be increased due to the influence of various external negative aspects on the body. You can check the level of the peptide during the test. At the same time, the indicators may differ in different cases. What affects it?

A low concentration of the peptide in the blood can be detected when:

Constant stress.
Hypoglycemic state in diabetics.

When a low level of the peptide is detected, the doctor informs the patient about this. Therapy is also given. It usually consists of taking appropriate medications that help increase peptide levels.

There may also be an increased level of the peptide. Such indicators occur in the following categories of people:

with beta cell hypertrophy.
With hormonal fluctuations.
With diabetes.
With poor kidney function.

What threatens C peptide increased? Doctors say that elevated levels of the substance in the blood do not pose a particular danger to humans. But with such indicators, appropriate therapy can be prescribed, with the help of which the rate of peptides can be reduced. The decision on the need for treatment is made by the doctor in each case individually based on the patient's condition.

Indications for analysis

Testing, which makes it possible to determine the presence of peptides in the blood, is important for patients with various pathologies. It is especially important for diabetics who have been diagnosed with various forms of the disease. Usually, such an analysis is recommended to be given to the patient by the doctor himself during therapy.

Typically, the analysis is prescribed for:

Control of the pancreas.
Polycystic ovaries.
Assessing the risk of developing pathologies in the fetus.
Infertility in women.
Suspicion of hypoglycemia.
Predicting diabetes.
Evaluation of the work of beta cells.
Formulating a treatment regimen for diabetes.

When conducting such a test, the doctor can determine the exact amount of the peptide in the blood and make a diagnosis based on the results. When the level of the substance is underestimated, the doctor may prescribe a treatment during which the hormone will be administered to the patient. Appropriate therapy is also prescribed for high level substances.

Test rules

Blood is taken for testing in the following way:

Blood is taken from a vein using a syringe. The material is placed after taking in a clean test tube.
A bandage is applied to the injection site.
A test tube with blood should be stored in a cold place at a temperature of up to minus 20 degrees until it is examined.

Usually tests are carried out in the morning. After donating blood, the patient can continue to eat in the usual way and not follow the diet. You can also continue to take the pills.

Deciphering the values

It is known that C-peptide can control insulin production. If a person has an underestimated amount of a substance, then it means that some pathologies occur in the body, and therefore the appearance of diabetes is also possible. This is usually possible at a lower rate.

When the rates are too high, type 2 diabetes can also develop. In this case, the patient will have pronounced hyperinsulinism. Also general state human health will be poor.

Research and its methodology

When testing in the laboratory, you can accurately determine the amount of peptides in the blood. To conduct research today, physicians have several ways. Some do tests on an empty stomach, while others give you the opportunity to stimulate the production process by eating carbohydrates. In any case, the material for the test is taken from a vein.

It is also noted that in order to obtain the most accurate result, several testing methods should be used. When decoding, a comparison of the test results is carried out. which were held at different times.

Each clinic has its own rules and regulations for decoding C-peptide indicators. Although such indicators are not the main ones when making a diagnosis in a particular case, nevertheless, they must be taken into account.

Who to contact?

It is necessary to take tests in the laboratory, and if negative symptoms appear, it is worth contacting an endocrinologist. He will evaluate the work of the pancreas and prescribe correct therapy. Also, women should visit a gynecologist. In any case, the treatment of pathologies should be carried out in a complex manner with the participation of different specialists.