Thyroid hormone and atherosclerosis

It is generally accepted that the euthyroid state is preferred for the cardiovascular system because both hyperthyroidism and hypothyroidism cause or accelerate cardiovascular diseases. And hypothyroidism is known to be associated with atherosclerosis and ischemic heart diseases. The accelerated atherosclerosis in hypothyroid state has been traditionally ascribed to atherogenic lipid profile, diastolic hypertension and impaired endothelial function. In addition, recent studies suggest that hypothyroidism is associated with the emerging risk factors for atherosclerosis such as hyperhomocysteinemia and an increase in C-reactive protein level. Thyroid hormone also has direct anti-atherosclerotic effects such as blood vessel dilatation, production of vasodilatory molecules, and inhibition of angiotensin II receptor expression and its signal transduction. These data suggest that thyroid hormone inhibits atherogenesis through direct effects on the vasculature as well as modifying risk factors for atherosclerosis. This review summarizes the basic and clinical studies on the role of thyroid hormone in atherogenesis and a possible application of thyroid hormone mimetics for the therapy of hypercholesterolemia and atherosclerosis.