Homocysteine

Vitamins B6, B12, and folate are necessary to metabolize homocysteine. People who are deficient in these vitamins may have increased levels of homocysteine.

According to the American Heart Association (AHA), some evidence suggests that excess homocysteine may promote atherosclerosis by damaging blood vessel walls and supporting the formation of inappropriate blood clots, but there is not a direct link between the two. The benefit of using homocysteine levels for risk assessment of cardiovascular disease (CVD), peripheral vascular disease, and stroke is uncertain given that several studies indicate no benefit or lowering of CVD risk with folic acid and B vitamin supplementation.

Homocysteine can be greatly increased in the blood and urine of people with a rare inherited condition called homocystinuria. This disorder is caused by an alteration in one of several different genes. The affected person has a dysfunctional enzyme that does not allow the normal breakdown of methionine. Because of this, homocysteine and methionine begin to build up in the person's body. A baby with this condition will appear normal at birth but within a few years will begin to develop signs such as a dislocated lens in the eye, a long slender build, long thin fingers, skeletal abnormalities, osteoporosis, and a greatly increased risk of thromboembolism and of atherosclerosis that can lead to premature cardiovascular disease. The buildup may also cause progressive mental retardation, behavioral disorders, and seizures.