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The causes of increase and decrease in homocysteine
Last reviewed: 19.10.2021
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High concentrations of homocysteine are the most important factor in the early development of atherosclerosis and thrombosis. Hyperhomocysteinemia is detected in 13-47% of IHD patients. Currently, the determination of serum homocysteine concentration is used as a marker for the development of IHD. The high concentration of homocysteine in the blood in patients with IHD is a clear harbinger of acute episodes that can lead to death. In terms of severity, hyperhomocysteinemia is divided into mild (15-25 μmol / l), moderate (25-50 μmol / l) and heavy (50-500 μmol / l). In patients with coronary artery disease with a homocysteine concentration in the blood below 10 μmol / L, stenosis of the coronary arteries is usually less than 50%, at a level of 10-15 μmol / l - 80%, above 15 μmol / l - 90%.
Congenital homocysteinuria is a monogenic metabolic defect caused by a deficiency of methylene tetrahydrofolate reductase. The concentration of homocysteine in the blood plasma (50-500 μmol / l) and its excretion in the urine are significantly increased in patients.
In heterozygotes for the defect of cystathionine-β-synthetase, the homocysteine concentration in the blood is within the normal range, so a load test with methionine is used to detect the disease. This test is carried out in 2 stages. Initially, the control study. A sample of blood is taken immediately after breakfast and after 2, 4, 6 and 8 hours. Normally, the transient peak of homocysteine concentration increase occurs at an interval between 4 and 8 hours. On the second day, blood for the studies is taken immediately before the load and after 2, 4, 6 and 8 hours after oral intake of methionine (100 mg / kg). The test is considered positive if the concentration of homocysteine in the blood during this time interval exceeds the results of the control test by an amount equal to or greater than 2 standard deviations.
Currently, the mechanisms that determine the role of increased concentration of homocysteine in the blood in the pathogenesis of atherosclerosis are actively discussed. A negative correlation was found between the concentrations in the blood of homocysteine and folate, as well as vitamins B 6 and B 12. Deficiency of these substances in the body is accompanied by an increase in the concentration of homocysteine in the blood. Use in the treatment of patients with hyper-homocysteinemia folates, vitamins B 6 and B 12 (cofactors of metabolites of methionine metabolism) has shown their effectiveness. With effective therapy, the serum homocystene concentration should not exceed 10 μmol / l.
Hyperhomocysteinemia can also be one of the manifestations of the neoplastic process, in particular, in breast, ovarian and pancreatic cancer, ALL. The increase in serum homocysteine concentration may hypothyroidism, heavy psoriasis, chronic administration of drugs theophylline, estrogensoderjath contraceptives, cytostatics (methotrexate) and antiepileptic drugs (phenytoin, carbamazepine), due to errors of metabolism and absorption of vitamin B 12 and folic acid.