Hypothyroidism and endothelial function: a marker of early atherosclerosis?

Endothelial dysfunction represents an important pathway thereby cardiovascular risk factors promote the development and progression of atherosclerosis. Hypothyroidism is associated with an increased cardiovascular risk, and the assessment of endothelium function is recognised an effective tool for the detection of evidence of preclinical cardiovascular alterations. Both vascular smooth muscle cells and endothelium play pivotal roles in modulating vascular tone and both are potential targets of thyroid hormone action. The pathogenesis of the association between endothelial dysfunction and hypothyroidism is complex and still not well established. The presence of traditional and emerging risk factors may contribute to the development of endothelium impairment, generating a chronic state of injury that triggers abnormal endothelial response. Levothyroxine replacement therapy is currently used for restoring euthyroidism and improving cardiovascular risk of hypothyroid patients. The decision to treat patients with subclinical hypothyroidism should depend on the presence of risk factors, rather than on a TSH threshold. However, the actual effectiveness of thyroid hormone substitution in reducing the risk of cardiovascular events, especially in subclinically hypothyroid patients, remains to be elucidated. Large multicenter, placebo-controlled prospective trials are necessary to address the issue. The article also discusses recent patents in this field.