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Homocysteine is a compound found in the blood that is produced by the breakdown of methionine. Elevated levels of homocysteine have been shown to be a risk factor for development of atherosclerosis and venous thrombosis. High homocysteine levels may be caused by a deficiency of folic acid or B vitamins in the diet, kidney disease, hypothyroidism, psoriasis, systemic lupus erythematosus, or medications such as methotrexate or phenytoin. Genetic variants may also cause hyperhomocystinemia.
Studies have shown that elevated homocysteine levels nearly double the risk of venous thrombosis; however, lowering the level does not appear to lower the risk of these events. The mechanism of this increased risk is not well understood. Homocysteine levels can be lowered by increasing the amount of folate and B vitamins in the diet or supplementation with commercially available combinations of vitamin B6, B12, and folate.
No specific guidelines exist regarding testing. Measurement of serum homocysteine levels may be prudent in patients with unexplained blood clots or atherosclerosis. Although preliminary studies have not shown that lowering levels lowers risk, supplementation may be advisable until this issue has been further defined.
Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.