An analysis of immunoreactive insulin allows you to evaluate the quality of the production of peptide hormone by the endocrine organ. Testing is carried out for people who have never before used substitutes for the natural peptide hormone. This is due to the fact that when using preparations containing an exogenous substance, antibodies are produced in the body that can distort the test results.
Immunoreactive insulin - what is it?
If you look for the answer to the question of what is IRI, then there is mainly information about the human hormone of a protein nature produced by pancreatic cells. Often, the definition of "immunoreactive" is not indicated in the description of the substance. This is not entirely true. The fact is that in this context, "immunoreactive" is not a property of a molecule, but a technique for performing research.
In laboratories, the test is performed using biochemical analyzers and other latest generation test systems. Using high-specific immunometric studies, it is precisely the level of insulin in the blood that is measured without identifying identical determinants in the form of proinsulin.
Hormone Overview
Insulin is a hormone of peptide nature. It is formed in beta cells of pancreatic islets of Langerhans . Synthesis and isolation is a rather complex process, which involves several stages. Initially, an inactive hormone precursor (proinsulin) is formed, which after a series of chemical transformations during maturation turns into an active form.
Proinsulin is a single chain polypeptide. In terms of immunological properties, these substances are very close. In single-membrane organoids, under the influence of proinsulin, the connecting amino acid molecule is separated and insulin is formed.
The intake of the hormone in the blood is coordinated mainly by an increase in the concentration of glucose in it. In the blood, insulin is divided into bound (free in combination with transferrin or alpha globulin). Types of the hormone differ from each other in their effect on insulin-sensitive tissues.
Insulin is a universal anabolic hormone that has a versatile effect on metabolic processes in almost all tissues. Its main effect is hypoglycemic effect. Insulin also affects other processes:
- It activates the transport of substances through the elastic molecular structure of the cell.
- Stimulates the formation of glycogen from glucose in the liver and muscles.
- It inhibits or completely inhibits gluconeogenesis.
- It inhibits the process of splitting fats into diglycerides and fatty acids.
- Promotes the formation of adenosine triphosphate, which plays a large role in the energy metabolism of cells.
The biological effect of the hormone can be ensured only on condition that the content of immunoreactive insulin in the blood is normal. Increased or decreased indicators indicate health problems.
The rate of IRI in the blood
In the body, several biologically active substances are responsible for an increase in blood sugar levels: cortisone, glucagon, adrenaline. And only one hormone helps to reduce it - insulin. Its content in the blood should be within normal limits, otherwise, malfunctions in the functioning of organs and systems occur and various pathologies are formed. There is a special unit called insulin, which determines the amount of hormone in the body. The indicators of insulin and glucose in the blood are completely different values.
Different laboratories may use different test systems, so the results must be checked against reference values. In the analysis for immunoreactive insulin, indicators are considered the norm in the range of 6-24 μU / ml. IRI is influenced by the age of the patient (values are measured in μU / ml):
- Children from birth to 6 years - 10-20.
- In children aged 6-10 years, 7.7 ± 1.3 are considered normal.
- 10-15 years - 13.2 ± 1.5.
- From 16 years old - 6-24.
Immunoreactive insulin is elevated - what does it mean?
The rate of secretion of the protein-peptide hormone is determined by the level of glucose in the blood and is determined by the state of the endocrine system, autonomic central nervous system and nutrition. In people with type 2 diabetes, insulin levels are usually elevated. This indicates the intensive work of the pancreas and the formation of insulin resistance. A high concentration of the hormone in the blood may be associated with other pathological manifestations.
- Obesity.
- Liver disease.
- The presence of neoplasms on the tissues of the pancreas.
- Diseases of the pituitary gland (pituitary gland).
- Muscular dystrophy.
- Itsenko-Cushing's syndrome.
- Intolerance to fruit sugar and galactose.
- Necidioblastosis.
- Insulinoma.
When decoding the indicators, it is necessary to take into account in which period the results are recorded. So, for example, the indicator of immunoreactive insulin 77 after exercise is considered the norm in the range from 30 to 120 minutes.
Lowered IRI
IRI analysis makes it possible to make the right conclusion for patients whose hormone levels are at the lowest or highest limits of established norms. Any deviations in one direction or another indicate that the patient has problems with the pancreas or diabetes.
A decrease in the level of the hormone in the blood indicates a malfunction in the endocrine organs. In diabetes mellitus, immunoreactive insulin is not always elevated. Lower rates also indicate the presence of endocrine disease, but not only 2, but 1 type. IRI below the norm may indicate other violations:
- Violations of the anterior pituitary gland (hypopituitarism).
- Addison's disease.
- Heavy and prolonged physical activity.
How is testing done?
An analysis of immunoreactive insulin is done after 8-12 hours of fasting. The laboratory assistant takes a blood sample into a special tube with an anticoagulating substance. Using a centrifuge, plasma and blood cells are separated and cooled to -40 ° C. After the liquid part of the blood has separated, it is frozen at -200 ° C. In this form, the biomaterial is placed in a test system and the results obtained are evaluated. In some laboratories, it is necessary to re-donate blood 2 hours after the first sampling to assess hormone secretion. The patient should remain hungry at the time of re-collection.
There is another research method. Glucagon-free insulin is administered to the patient on an empty stomach orally or in a vein at the rate of 0.1 PIECES per kg of weight. After that, blood samples are taken every 30 minutes for 2 hours. Normal values (mkED / ml) should look as follows:
- 30 minutes after exercise, immunoreactive insulin increased to 25-231.
- 60 minutes - 18-277.
- 120 minutes - 16-167.
- 180 - 4-18.
Based on observations, it is noted that when glucose is administered orally, insulin release is greater than when administered intravenously. It is also noted that with age, the pancreas loses sensitivity to glucose, but the level of maximum secretion remains constant.
What is analysis used for?
Tests for the content of IRI help not only insulin-dependent people in determining the type of diabetes. Analysis allows certain observations and studies of the health status of people with endocrine diseases characterized by impaired glucose uptake. Testing is used for:
- Studies of the role of insulin in the mechanism of development of diabetes mellitus.
- Studies of insulin metabolism in pregnant women with diabetes.
- Detection of insulin resistance in the early stages.
- Calculation of the exact start time of taking hypoglycemic agents for type 2 diabetes.
- Identification of the causes of chronic hypoglycemia (IRI analysis is carried out in combination with a C-peptide test and glucose analysis).
Indications for the test
An immunoreactive insulin test is prescribed by a therapist, endocrinologist or gastroenterologist. Indications for the study are the following indicators:
- Weight gain with a constant diet.
- Prolonged healing of skin injuries.
- Detection of protein in the analysis of urine.
- The presence of symptoms indicating the development of metabolic syndrome.
- Suspected insulin.
- Clinical manifestations of hypoglycemia: excessive sweating, a constant feeling of hunger, decreased visual acuity.
- Routine monitoring after transplantation of pancreatic endocrine cells.
Endocrine diseases tend to progress rapidly. Their identification is extremely important in the initial stages. At the first suspicious symptoms, consult a doctor.
Analysis preparation
The test for immunoreactive insulin allows you to recognize diseases at the very beginning of their formation. In patients diagnosed with diabetes mellitus, the analysis allows you to determine the type of disease with absolute accuracy, and during which period (if type 2 diabetes) should start taking hypoglycemic drugs. In order for the results to be accurate, it is necessary to fulfill a number of requirements for preparing for the study.
- Completely exclude food intake 8-12 hours before the test.
- Discontinue use of the drug 2 weeks before testing. If the patient due to health reasons must constantly use medication, notify the doctor about this.
- For a day, exclude any physical activity.
- For 12 hours you can not eat salty, fried foods, alcoholic beverages.
- An hour before testing, you must refrain from smoking.
Analysis is recommended in the morning. On the eve it is advisable to lie down early and get enough sleep, try to avoid nervous tension. In the morning you are allowed to drink a glass of plain water.
Methods of biomaterial collection and delivery to the laboratory
Blood when tested for immunoreactive insulin is taken from a vein using vacuum systems. The convenience of such systems lies in a removable needle holder with a tube adapter. This design allows for a single puncture of the vein to carry out several fences of biomaterial. This is very important when conducting an analysis for insulin tolerance, since the patient’s blood is taken 5 times throughout the test.
When taking biomaterial, use the standard technique for obtaining venous blood. As an anticoagulant (a drug that inhibits blood coagulation), heparin is used. Blood is immediately centrifuged at a temperature of + 4 ° C. Serum and plasma are placed in secondary tubes and, if necessary, transported.
Storage conditions for biomaterial
The reliability of the analysis results depends on a number of conditions, including the complex of external environmental influences, depending on the mode of blood storage. Biomaterial for research is often required to be delivered to the laboratory. Transportation and storage is carried out based on the physical properties of the hormone.
- In freshly citrated blood with becks and cells inside it (white blood cells, platelets), insulin is stable for 60 minutes.
- In blood plasma without the liquid part remaining after coagulation (fibrinogen), the hormone is stable for 4 hours at a temperature of 22-25 degrees Celsius.
- Longer storage of biomaterial, but not more than 24 hours, is carried out in the refrigerator at a temperature of +4 to + 8 ° C.
What affects the distortion of indicators?
False results are most often the result of non-compliance with the rules of preparation for analysis. In most cases, incorrect indicators are due to the use of various drugs.
Increased immunoreactive insulin can be if the patient was taking Albuterol (treatment of bronchial asthma), Levodop (parkinsonism therapy), Medroxyprogesterone (antitumor), and oral contraceptives. An increase in hormone concentration is also observed in the second and third trimester of pregnancy.
Propranolol (treatment of arterial hypertension), Cimetidine (antihistamine), thiazide diuretics, ethanol cause a decrease in insulin concentration. Long-term physical activity also contributes to a decrease in hormone levels.
Where can I get an IRI test?
Usually, the doctor gives the direction for analysis indicating the place of his passage. But if a person wants to undergo an examination on his own, then first of all he has a question: "Where to pass immunoreactive insulin?"
To pass the test, it is better to choose a well-established laboratory. In Moscow, you can apply for the procedure at MobilMed, DNCOM, Helix. Such medical laboratory centers usually have a wide regional network. The only thing is to clarify the cost of the analysis directly at the intended location.