The relation between thyroid disfunction and heart diseases has beenlargely recognized. Throw gene codification and regulation, as so extranuclear influences, the thyroid hormone leads important modifications in cardiac myocite in his function and struture. There is no doubt that hypertyreoidism means more morbidity, increasing, sometimes mortality. But the cardiac manifestations in hypothyreoidism are also responsable by worst prognostic in some clinical conditions. In this review, will be presented fisiopatologic pathways of triiodotironine in cardiovascular enviroment, as consequences of thyroid disorders in genesis or worse of heart diseases.