Hyperhomocysteinemia, caused by a lack of folic acid and methionine in a monkey diet, induces endothelial dysfunction, which is characterized by an impaired vasodilation response to acetylcholine or adenosine diphosphate, decreased anticoagulant activity of thrombomodulin, and increased platelet‐mediated collagen infusion vasoconstriction (Lentz et al., 1996). Here, THBD is linked to hyperhomocysteinemia.