Hyperhomocysteinemia is a medical condition characterized by an abnormally high level of homocysteine in the blood, conventionally described as above 15 μmol/L.As a consequence of the biochemical reactions in which homocysteine is involved, deficiencies of
vitamin B6, folic acid (vitamin B9), and vitamin B12 can lead to high homocysteine levels. Other possible causes of hyperhomocysteinemia include genetics, excessive methionine intake, and other diseases. Hyperhomocysteinemia is typically managed with vitamin B6, vitamin B9 and vitamin B12 supplementation. Hyperhomocysteinemia is a risk factor for cardiovascular disease; however, supplements of these vitamins may not improve cardiovascular disease outcomes. Signs and symptoms
Elevated levels of homocysteine have been associated with a number of disease states. Cardiovascular risks
Elevated homocysteine is a known risk factor for cardiovascular disease as well as thrombosis. It has also been shown to be associated with microalbuminuria which is a strong indicator of the risk of future cardiovascular disease and renal dysfunction. Homocysteine degrades and inhibits the formation of the three main structural components of arteries: collagen, elastin and proteoglycans. In proteins, homocysteine permanently degrades cysteine disulfide bridges and lysine amino acid residues, affecting structure and function. Neuropsychiatric illness
Evidence exists linking elevated homocysteine levels with vascular dementia and Alzheimers disease. There is also evidence that elevated homocysteine levels and low levels of vitamin B6 and B12 are risk factors for mild cognitive impairment and dementia. Oxidative stress induced by homocysteine may also play a role in schizophrenia. Bone health
Elevated levels of homocysteine have also been linked to increased fractures in elderly persons.
When combined with medicine to reduce blood pressure (antihypertensive drugs), it is not clear if treatments that lower homocysteine can help prevent a stroke in some people. Hypotheses have been offered to address the failure of homocysteine-lowering therapies to reduce cardiovascular events. When folic acid is given as a supplement, it may increase the build-up of arterial plaque. A second hypothesis involves the methylation of genes in vascular cells by folic acid and vitamin B12, which may also accelerate plaque growth. Finally, altered methylation may catalyse l-arginine to asymmetric dimethylarginine, which is known to increase the risk of vascular disease. See also
Homocystinuria
Kilmer S. McCully

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