Contents
The body has certain mechanisms that make sure that the blood is always in a liquid state and does not clot. These mechanisms include: rapid blood flow through the vessels, a smooth surface of the vascular wall covered with fibrin, negative charges of the endothelium and blood cells, which prevents them from sticking to each other. The body also has its own anticoagulants that keep the blood fluid. These anticoagulants can be primary (they are always present in the blood) and secondary (their body produces only when the need arises). Antithrombin (At) belongs to both the primary and secondary groups of anticoagulants. Antithrombin II is heparin, antithrombin III is plasma factor heparin, and antithrombin IV is alpha-2-macroglobulin. Only fibrin (antithrombin I) is a secondary natural anticoagulant that prevents blood from clotting when needed.
In laboratory studies, it is possible to detect antithrombin III in order to assess the anticoagulant abilities of the blood.
What is the diagnostic value of antithrombin III?
The level of antithrombin III has a relationship with a person’s age:
A newborn baby may have an antithrombin III level of 40-80%.
In children aged 1 month to 6 years, the limits of the antithrombin III norm are 80-140%.
In children from 6 to 11 years old, this figure should normally be 90-130%.
From 11 to 16 years of age, antithrombin III remains at around 80-120%.
For an adult, the normal level of this anticoagulant is 75-125%.
Antithrombin III is important in diagnostic terms precisely because it takes over most of the plasma antithrombin activity. Other anticoagulants also prevent blood clotting, but to a lesser extent. The main task of antithrombin III is the production of thrombin, as well as the inhibition of such blood factors as: urokinase, plasmin, kallikrein, VII, IX-XII.
It should be noted that the anticoagulant activity of antithrombin III is enhanced only in conjunction with heparin. This complex accounts for up to 80% of all antithrombotic capabilities of human blood.
What does the deficiency and excess of antithrombin III indicate?
If a person has a reduced level of antithrombin III, then this may signal the following conditions:
The woman has been taking hormonal drugs for a long time to prevent unwanted pregnancy.
Postponed surgery or injury.
A person has been immobilized for a long time.
Treatment with L-asparaginase.
Taking heparin in high doses, which contributes to the destruction of antithrombin III.
Lack of ovulation in a woman of childbearing age.
Profuse bleeding.
Long-term use of corticosteroid drugs.
Age-related hereditary thromboembolism and a person’s genetic predisposition to a lack of antithrombin.
DIC, consumption coagulopathy.
Liver failure against the background of various diseases: cirrhosis, liver tumors, etc.
The presence of a malignant tumor in the body.
Thrombosis.
Sepsis.
Shock condition.
The introduction into the body of drugs to stop blood loss: fibrinogen, fibrinostat, cryoprecipitate.
Nephrological syndrome in which there is excessive excretion of antithrombin III in the urine.
The following conditions can lead to an increase in the level of antithrombin III in the body:
Viral hepatitis in the acute stage.
Reception of indirect anticoagulants.
Vitamin K deficiency in the body.
Cholestasis.
Acute or chronic inflammation in the body.
Taking anabolic hormones.
Qualitative and quantitative violations
Low levels of antithrombin III are rare. According to statistics, there are no more than 1% of such people in the world. However, of all the pathologies of the hematopoietic system, it is hereditary anticoagulant deficiency that is the most common violation.
Congenital deficiency of antithrombin III (heterozygous form of the pathological gene) is manifested by the development of thrombosis in people aged 20-35 years. Triggering factors are: pregnancy, childbirth, surgery or acute inflammation of the internal organs, taking hormonal contraceptives. In the homozygous form, thrombosis will develop immediately after birth, but such a violation is extremely rare.
Acquired antithrombin III deficiency can develop at any time, regardless of a person’s age.
A person is not able to independently determine the existing coagulant deficiency, since there are no symptoms of a violation. The only sign of this pathology will be the formation of thrombosis, but they develop not only with a lack of antithrombin III, but also with other disorders of the hematopoietic system. Moreover, blood clots are able to form in the vessels even at a normal level of At III. Just with its structural changes, antithrombin may cease to perform the functions assigned to it.
Therefore, there is a quantitative deficiency of antithrombin III and a qualitative deficiency of antithrombin III. The first type of disorders is characterized by a low content of antithrombin III in the blood, and the second type is characterized by its functional inferiority. Moreover, in both of these conditions, thrombosis can develop. To find out what exactly led to the formation of blood clots in the vessels, a qualitative study of the antithrombin factor is required.
Deficiency and excess of antithrombin III during pregnancy
The body of a pregnant woman from the very moment of conception begins to prepare for childbirth. At the same time, preparation takes place in the entire hemostasis system, which affects the state of the anticoagulant factor. To a greater extent, these changes are noticeable during the third trimester of pregnancy.
The body seeks to prevent the development of bleeding during labor, therefore, it increases the level of clotting factors in the blood. Plasma fibrinolytic activity decreases, the level of clotting inhibitors, including antithrombin III, falls. This becomes noticeable precisely towards the end of the third trimester. However, normally, the level of antithrombin III should not fall below 65%.
Sometimes with hereditary deficiency of antithrombin III, its fall is erased, which cannot be determined in the laboratory. This is especially often observed during pregnancy, which is accompanied by severe toxicosis. This condition is dangerous in that an artificial termination of pregnancy is possible, and after childbirth, a woman may develop venous or arterial thrombosis, infarction of internal organs or pulmonary embolism. Therefore, if the patient is at risk for this condition, then she should be under special control by the doctor.
An increase in antithrombin III during pregnancy threatens the development of bleeding. This happens against the background of severe pathologies, for example, with cholestasis or acute hepatitis.
Conclusion
Antithrombin III is essential to human health. With severe deficiency, the patient develops a severe form of thrombosis and embolism. Sometimes the disease manifests itself immediately after the birth of the child. A latent form of antithrombin III deficiency may not make itself felt for a long time, but all this time a person will be in real danger, the main of which is the separation of a blood clot.
If the level of antithrombin decreases to 65-45%, then this condition leads to the formation of a small number of blood clots, which begin to appear at the age of 20-35 years. At the same time, provoking factors should act on the human body. Therefore, in order to reduce the risk of thrombosis, it is necessary to control the level of antithrombin in the blood and avoid situations that can provoke the formation of blood clots in the veins.