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*Only for medical professionals to read and reference Why do these tests? How to do it What are the precautions during the test? In the Department of Endocrinology, diabetic patients, especially newly diagnosed patients, often need to check pancreatic islet function.
The main methods for checking pancreatic islet function are insulin and C-peptide release tests.
These two tests are very important for diagnosing diabetes, judging the type and prognosis, and guiding treatment.
But "why do these tests? How should they be done? What are the test procedures? Matters needing attention?" The author will refer to the literature below to specifically talk about the "insulin, C-peptide release test".
1.
Insulin and C-peptide are twin brothers, which can effectively reflect the function of insulin secretion.
Insulin is a hormone secreted by the pancreas that regulates glucose metabolism.
It can promote the uptake and utilization of glucose by tissues such as liver, muscle and fat.
The rise in blood sugar is accompanied by insulin.
As the level increases, the secretion curves of the two are parallel; C-peptide, also known as connecting peptide, is the "twin brother" of insulin and has a common precursor (proinsulin), so in theory, C-peptide and insulin are the same secretion of.
Studies have found that insulin is mostly degraded when the blood passes through the liver and kidneys after it is released, and C-peptide is not easily degraded by the liver, and its half-life is longer than that of insulin.
For patients who have been treated with insulin and may have produced insulin antibodies in their body, since there is no cross-immune reaction between C-peptide and insulin, it can overcome the interference of insulin receptors, and the injected exogenous insulin does not contain C-peptide, so it is determined The level of C-peptide in the blood can reflect the level of endogenous insulin, that is, it can reflect the secretory function of pancreatic islets more accurately and truly.
Clinically, the determination of C-peptide is often carried out at the same time as the determination of insulin.
Understanding the reserve function of pancreatic β-cells is also helpful for the classification of diabetes and the guidance of treatment.2.
Who needs insulin and C-peptide release test? 1.
People with a family history of diabetes and typical symptoms of "three more and one less", that is, polydipsia, polyuria, polyphagia, weight loss (weight loss) symptoms, or monitor blood sugar higher than normal; 2.
Obesity, fatty liver, high People with various metabolic abnormalities such as blood pressure, hyperlipidemia, and hyperuric acid; 3.
Diabetes patients should be checked once a year; 4.
People with positive urine glucose; 5.
Follow-up for patients with previous impaired glucose tolerance; 6.
Frequent hypoglycemia: such as palpitation , Sweating, hungry, collapse; 7.
excessive weight gain during pregnancy, suspected of gestational diabetes; 24 to 28 weeks of normal pregnancy, spontaneous abortion, premature delivery, stillbirth or history of large babies in previous pregnancy; suspected of polycystic Those with ovarian syndrome.
3.
What should I do for insulin and C-peptide release test? Clinically, insulin and C-peptide release tests are often carried out simultaneously with oral glucose tolerance tests.
The standard operation process is as follows: give the patient a quantitative oral glucose (standard glucose 75g) or steamed bread (100g standard flour) when the patient is fasted (8-10 hours fasting) Buns) to increase blood sugar, stimulate insulin beta cells to release C-peptide and insulin, measure blood sugar and plasma insulin at the 5 time points of 30 minutes, 60 minutes, 120 minutes, and 180 minutes after fasting and after taking sugar (or steamed buns).
C peptide level and record.
4.
What details should be paid attention to in insulin and C-peptide release test? 1.
Discontinue drugs that may affect glucose metabolism 3-7 days before the test, stop drugs that may affect glucose metabolism, such as glucocorticoids, contraceptives, thiazide diuretics, sulfa drugs, propranolol, etc.
2.
The intake of carbohydrates should be controlled, but should not be excessively restricted.
Since 3 days before the test, the daily intake of carbohydrates should not be less than 150g, but should be controlled within the range of 250～300g, and normal activities should be maintained.
.
3.
Sugar water preparation, taking and timing details instruct the patient to fast for 8-10 hours, draw venous blood on an empty stomach before 8 o'clock in the morning, and then orally take 75g of anhydrous dextrose powder dissolved in 300mL warm water, such as 1 molecule of water dextrose 82.
5g (for children 1.
75g per kilogram of body weight) syrup should be drunk within 3 to 5 minutes, counting from the first sip, taking venous blood at 30 minutes, 60 minutes, 120 minutes and 180 minutes, respectively, and measure the above Blood glucose, insulin and C-peptide values at 5 time points.
Blood samples should be submitted for examination as soon as possible.
If the subjects cannot tolerate glucose water, they can also choose steamed buns (about 3 taels) made of 100 grams of flour instead of glucose water.
4.
Avoid doing glucose tolerance tests under stress, keep a calm mind, avoid mental stimulation, fever, infection, surgery, acute myocardial infarction, stroke and other stress states that will cause blood sugar to rise and make the result false positive, so the patient The inspection can only be carried out after the stress state has passed.
During the experiment, the subjects should not drink tea, coffee, smoke, or do strenuous exercise, but they do not need to stay in bed absolutely.
5.
Tests requiring fasting fingertip blood glucose <10mmol/L generally require subjects to measure fasting fingertip blood glucose less than 10 mmol/L.
If fasting blood glucose exceeds 10 mmol/L, this test is not recommended.
Otherwise, due to the toxic effects of hyperglycemia, the secretion of insulin and C-peptide is obviously inhibited, and the measured results cannot reflect the true condition of the subject's islet function.
Moreover, giving patients oral sugar water when the blood sugar is high will cause the blood sugar to rise further, and even induce diabetic ketoacidosis, which will cause unnecessary damage to the subjects.
Therefore, if the patient's blood sugar is high, it is best to perform intensive treatment first.
After the fasting blood sugar drops below 8mmol/L (maximum 10mmol/L), check again after 3 to 5 days.
6.
The test should be terminated if nausea, vomiting or other foods are consumed during the test.
References: [1].
Han Guangyu, Xu Zhan, Shi Li, Li Quanshuang, Liang Jun, Zhang Wei.
Analysis of the results of serum insulin C peptide release test in patients with type 2 diabetes and impaired glucose tolerance[J].
Chinese School Doctor,2016, 30(07):541-543.
[2].
Li Feng.
The relationship between C-peptide and blood glucose control, complications and metabolic indexes in patients with type 2 diabetes[J].
New World of Diabetes,2020,23(23):47 -48+51.
[3].
Hu Shaowen Guo Ruilin Practical Diabetes[M].
Beijing People’s Military Medical Publishing House 2003:45-48.
The main methods for checking pancreatic islet function are insulin and C-peptide release tests.
These two tests are very important for diagnosing diabetes, judging the type and prognosis, and guiding treatment.
But "why do these tests? How should they be done? What are the test procedures? Matters needing attention?" The author will refer to the literature below to specifically talk about the "insulin, C-peptide release test".
1.
Insulin and C-peptide are twin brothers, which can effectively reflect the function of insulin secretion.
Insulin is a hormone secreted by the pancreas that regulates glucose metabolism.
It can promote the uptake and utilization of glucose by tissues such as liver, muscle and fat.
The rise in blood sugar is accompanied by insulin.
As the level increases, the secretion curves of the two are parallel; C-peptide, also known as connecting peptide, is the "twin brother" of insulin and has a common precursor (proinsulin), so in theory, C-peptide and insulin are the same secretion of.
Studies have found that insulin is mostly degraded when the blood passes through the liver and kidneys after it is released, and C-peptide is not easily degraded by the liver, and its half-life is longer than that of insulin.
For patients who have been treated with insulin and may have produced insulin antibodies in their body, since there is no cross-immune reaction between C-peptide and insulin, it can overcome the interference of insulin receptors, and the injected exogenous insulin does not contain C-peptide, so it is determined The level of C-peptide in the blood can reflect the level of endogenous insulin, that is, it can reflect the secretory function of pancreatic islets more accurately and truly.
Clinically, the determination of C-peptide is often carried out at the same time as the determination of insulin.
Understanding the reserve function of pancreatic β-cells is also helpful for the classification of diabetes and the guidance of treatment.2.
Who needs insulin and C-peptide release test? 1.
People with a family history of diabetes and typical symptoms of "three more and one less", that is, polydipsia, polyuria, polyphagia, weight loss (weight loss) symptoms, or monitor blood sugar higher than normal; 2.
Obesity, fatty liver, high People with various metabolic abnormalities such as blood pressure, hyperlipidemia, and hyperuric acid; 3.
Diabetes patients should be checked once a year; 4.
People with positive urine glucose; 5.
Follow-up for patients with previous impaired glucose tolerance; 6.
Frequent hypoglycemia: such as palpitation , Sweating, hungry, collapse; 7.
excessive weight gain during pregnancy, suspected of gestational diabetes; 24 to 28 weeks of normal pregnancy, spontaneous abortion, premature delivery, stillbirth or history of large babies in previous pregnancy; suspected of polycystic Those with ovarian syndrome.
3.
What should I do for insulin and C-peptide release test? Clinically, insulin and C-peptide release tests are often carried out simultaneously with oral glucose tolerance tests.
The standard operation process is as follows: give the patient a quantitative oral glucose (standard glucose 75g) or steamed bread (100g standard flour) when the patient is fasted (8-10 hours fasting) Buns) to increase blood sugar, stimulate insulin beta cells to release C-peptide and insulin, measure blood sugar and plasma insulin at the 5 time points of 30 minutes, 60 minutes, 120 minutes, and 180 minutes after fasting and after taking sugar (or steamed buns).
C peptide level and record.
4.
What details should be paid attention to in insulin and C-peptide release test? 1.
Discontinue drugs that may affect glucose metabolism 3-7 days before the test, stop drugs that may affect glucose metabolism, such as glucocorticoids, contraceptives, thiazide diuretics, sulfa drugs, propranolol, etc.
2.
The intake of carbohydrates should be controlled, but should not be excessively restricted.
Since 3 days before the test, the daily intake of carbohydrates should not be less than 150g, but should be controlled within the range of 250～300g, and normal activities should be maintained.
.
3.
Sugar water preparation, taking and timing details instruct the patient to fast for 8-10 hours, draw venous blood on an empty stomach before 8 o'clock in the morning, and then orally take 75g of anhydrous dextrose powder dissolved in 300mL warm water, such as 1 molecule of water dextrose 82.
5g (for children 1.
75g per kilogram of body weight) syrup should be drunk within 3 to 5 minutes, counting from the first sip, taking venous blood at 30 minutes, 60 minutes, 120 minutes and 180 minutes, respectively, and measure the above Blood glucose, insulin and C-peptide values at 5 time points.
Blood samples should be submitted for examination as soon as possible.
If the subjects cannot tolerate glucose water, they can also choose steamed buns (about 3 taels) made of 100 grams of flour instead of glucose water.
4.
Avoid doing glucose tolerance tests under stress, keep a calm mind, avoid mental stimulation, fever, infection, surgery, acute myocardial infarction, stroke and other stress states that will cause blood sugar to rise and make the result false positive, so the patient The inspection can only be carried out after the stress state has passed.
During the experiment, the subjects should not drink tea, coffee, smoke, or do strenuous exercise, but they do not need to stay in bed absolutely.
5.
Tests requiring fasting fingertip blood glucose <10mmol/L generally require subjects to measure fasting fingertip blood glucose less than 10 mmol/L.
If fasting blood glucose exceeds 10 mmol/L, this test is not recommended.
Otherwise, due to the toxic effects of hyperglycemia, the secretion of insulin and C-peptide is obviously inhibited, and the measured results cannot reflect the true condition of the subject's islet function.
Moreover, giving patients oral sugar water when the blood sugar is high will cause the blood sugar to rise further, and even induce diabetic ketoacidosis, which will cause unnecessary damage to the subjects.
Therefore, if the patient's blood sugar is high, it is best to perform intensive treatment first.
After the fasting blood sugar drops below 8mmol/L (maximum 10mmol/L), check again after 3 to 5 days.
6.
The test should be terminated if nausea, vomiting or other foods are consumed during the test.
References: [1].
Han Guangyu, Xu Zhan, Shi Li, Li Quanshuang, Liang Jun, Zhang Wei.
Analysis of the results of serum insulin C peptide release test in patients with type 2 diabetes and impaired glucose tolerance[J].
Chinese School Doctor,2016, 30(07):541-543.
[2].
Li Feng.
The relationship between C-peptide and blood glucose control, complications and metabolic indexes in patients with type 2 diabetes[J].
New World of Diabetes,2020,23(23):47 -48+51.
[3].
Hu Shaowen Guo Ruilin Practical Diabetes[M].
Beijing People’s Military Medical Publishing House 2003:45-48.
