Homocysteine
Sulfur amino acid intermediate of methionine metabolism whose plasma elevation reflects impaired remethylation (folate, B12, riboflavin) or transsulfuration (B6) and is an independent risk marker for cardiovascular disease.
Also: Hcy, tHcy
Homocysteine is remethylated to methionine by methionine synthase (B12, 5-methyl-THF) or BHMT (betaine), or transsulfurated to cystathionine by cystathionine β-synthase (B6). Total plasma Hcy >15 μmol/L is mild hyperhomocysteinemia. Severe elevation occurs in CBS deficiency (homocystinuria). RCTs of B-vitamin lowering of Hcy have shown lower stroke risk but minimal effect on coronary endpoints, motivating MNHD's cautious position on Hcy as a treatable target.
How one textbook covers it
Modern Nutrition in Health and Disease, 12th ed. — Ch 30: Sulfur Amino Acids and Homocysteine
Homocysteine is remethylated to methionine by methionine synthase (B12, 5-methyl-THF) or BHMT (betaine), or transsulfurated to cystathionine by cystathionine β-synthase (B6). Total plasma Hcy >15 μmol/L is mild hyperhomocysteinemia. Severe elevation occurs in CBS deficiency (homocystinuria). RCTs of B-vitamin lowering of Hcy have shown lower stroke risk but minimal effect on coronary endpoints, motivating MNHD's cautious position on Hcy as a treatable target.
Related terms
Folate, MTHFR, Methionine, SAM, Vitamin B12