The crosstalk between thyroid hormones and the Renin-Angiotensin System

Thyroid hormones (THs) exert multiple effects on the heart and vascular system. As a consequence, altered cardiovascular function observed in the thyroid diseases corresponds to one of the most important and clinically relevant aspects found in both hyperthyroidism and hypothyroidism. Besides THs' direct effects on the heart and vascular system, in the last three decades several studies have implicated the Renin-Angiotensin System (RAS) in some of the cardiovascular effects of THs, with this interaction suggesting that RAS may be an important mediator of THs actions. In the present review, we discuss the alterations in the circulating RAS, as well as modifications in cardiac and vascular RAS which are involved in the cardiovascular alterations found during the modulation of TH levels. In addition, considering the important role that both systems present during fetal and neonatal periods, we also review the interaction between THs and the RAS in the development of cardiovascular system. A greater understanding of the role of the RAS in hyperthyroidism and hypothyroidism, during early or adult life will presumably facilitate the evolution of newer, targeted therapies. (C) 2009 Elsevier Inc. All rights reserved.