Homocysteine is a naturally occurring, sulfur-containing amino acid in the blood that requires enzymes, vitamin B12, folic acid, and other vitamins to be converted to the essential amino acid methionine. Several conditions (such as deficiencies of certain vitamins in the body, kidney failure, hypothyroidism, or genetic defects) may cause homocysteine levels to rise.
Hyperhomocysteinemia is a medical condition characterized by high levels of homocysteine (an amino acid) in the blood. Patients with hyperhomocysteinemia have an increased risk of developing coronary artery disease (CAD), because high levels of homocysteine may irritate blood vessels, and this may then lead to blockages in arteries. In addition, clots become stronger and less likely to break down naturally. Such changes make vessels vulnerable to clots, obstructions, and disease.
Deficiencies in folic acid (folate), vitamin B6, vitamin B12, or betaine may lead to hyperhomocysteinemia. The concentration of homocysteine in the blood will decrease after appropriate supplementation with the deficient vitamins.
Patients with kidney failure who are undergoing dialysis also have an increased risk of developing hyperhomocysteinemia. However, researchers have not discovered exactly why this condition sometimes develops in dialysis patients.
Hyperhomocysteinemia does not cause any symptoms. Therefore, the American Heart Association recommends regular homocysteine testing in patients who have high risks of developing heart disease.
Hyperhomocysteinemia is diagnosed after a blood test, called a homocysteine test. Patients who have greater than 15 micromoles of homocysteine per liter of blood with a fasting blood test are diagnosed with the condition.

Related Terms

Atherosclerosis, betaine, betaine anhydrous, cardiovascular disease risk, cerebral artery disease, choline, cocamidopropylbetaine, coronary artery disease, dialysis, fasting blood test, folate (vitamin B9), folic acid (vitamin B9), homocysteine, homocysteine test, homocystinuria (cystathionine beta-synthase deficiency), hyperhomocysteinemia, kidney failure, methylenetetrahydrofolate reductase (MTHFR) enzyme, methylenetetrahydrofolate reductase (MTHFR) gene, niacin, vitamin B6 (pyroxidine), vitamin B12.