Thyroid Replacement Therapy and Heart Failure

H eart failure (HF) is a major public health and economic problem in Western countries and is one of the most common causes of hospitalization and death.Coronary artery disease is the underlying cause in more than two thirds of chronic HF patients.By 2020, the World Health Organization projects that ischemic heart disease alone will be the most important global cause of morbidity and mortality.The estimated increases in HF-related morbidity and mortality suggest that our understanding of the pathophysiological mechanisms of this syndrome is inadequate.Interest in the role of thyroid hormones (THs) in HF has increased in recent years.The driving considerations can be summarized as follows: (1) the known effects of THs on contractile and relaxation properties of the heart; (2) experimental findings offering strong support for the hypothesis that TH signaling is critical in preserving cardiac structure and performance under normal conditions and after cardiac injury; and (3) evidence that mildly altered TH function is strongly associated with a worsening prognosis in cardiac patients in general and in HF patients in particular.Diastolic function and systolic function are clearly influenced by THs. 1 Ventricular contractile function is also influenced by changes in hemodynamic conditions secondary to TH effects on peripheral vascular tone. 1 TH homeostasis preserves positive ventricular-arterial coupling, leading to a favorable balance for cardiac work.4]56 This review highlights a growing body of evidence from animal studies and small-scale clinical trials suggesting that low cellular thyroid activity at the cardiac tissue level may adversely affect HF progression and that treatment may lead to improvement.