Molecular and Subcellular Mechanisms of Thyroid Hormone Induced Cardiac Alterations

Abstract

The cardiovascular effects of excess thyroid hormone were first described by Parry 200 years ago (1), and the effects of thyroid deficiency have similarly been long recognized (2). Since the cardiac effects of thyroid hormone excess and deficiency are prominent, considerable research has focused on the mechanism by which thyroid hormone induces these changes. A number of reviews have been published which summarize the clinical and experimental literature regarding thyroid hormone effects on the heart (3–5). The intent of this chapter is to present the principal areas of investigation concerned with the effects of thyroid hormone action on the heart. Clinical and experimental consequences of thyroid disease on the heart are briefly presented, followed by a review of molecular and subcellular effects of thyroid hormone. Research directed towards understanding the effects of thyroid hormone on these latter two aspects of the heart has led to considerable insight into mechanisms responsible for the behavior of the heart in thyroid disease. Throughout this chapter the hormones of the thyroid gland, 3,5,3’,5’-tetraiodothyronine (thyroxine) and 3,5,3’-triiodothyronine, will be referred to as T4 and T3, respectively, or nondistinctively as thyroid hormone.