[Heart and thyroid interactions].

Thyroid dysfunction is a quite common clinical condition in the general population and often completely misunderstood. Thyroid hormones play a crucial role in the cardiovascular (CV) system contributing to the control of cardiac function and peripheral hemodynamics. In addition, they are involved in the regulation of glucose, lipid and coagulation homeostasis, further affecting CV risk stratification. The aim of the present article is to systematically review and summarize the available evidence on the possible association between thyroid dysfunction and CV morbidity and mortality. Overt hypothyroidism and hyperthyroidism significantly increase CV risk through either direct (on myocardial cell and coronary flow) and indirect (influencing the peripheral vascular system, lipid and glucose metabolism and coagulation homeostasis) mechanisms. Less clear is the contribution of subclinical conditions of hyperthyroidism and hypothyroidism to the stratification of CV risk. Treatment of subclinical hypothyroidism seems to guarantee greater benefits, especially in younger subjects at low CV risk. On the other hand, the treatment of subclinical hyperthyroidism allows greater advantages in older patients with a greater burden of associated comorbidities.