In the last 10 years, homocysteine (Hcy) has been regarded as a marker of cardiovascular disease and a definite risk factor for many other diseases. Hcy is biosynthesized from methionine through multiple steps and then goes through one of two major metabolic pathways: remethylation and transsulfuration. Hyperhomocysteinemia (HHcy) is a state in which too much Hcy is present in the body. The main cause of HHcy is a dysfunction of enzymes and cofactors associated with the process of Hcy biosynthesis. Other causes include excessive methionine intake, certain diseases and side effects of some drugs. HHcy is a trigger for many diseases, such as atherosclerosis, congestive heart failure, age-related macular degeneration, Alzheimer’s disease and hearing loss. There are many studies showing a positive relationship between Hcy level and various symptoms. We speculate that a high level of Hcy can be the sole reason or an aggravating factor in numerous diseases for which causal links are not fully understood.

Homocysteine; Hyperhomocysteinemia; Pathophysiology