Cardiovascular morbidity and mortality in thyroid dysfunction.

This review summarizes present knowledge from clinical and epidemiological studies with respect to cardiovascular complications in thyroid disorders, focusing on cardiovascular morbidity and mortality. Consistently, good evidence exists for an increased cardiovascular morbidity in overt hyperthyroidism, and an association with predictors of cardiovascular mortality like ventricular hypertrophy, ventricular dysfunction, and atrial fibrillation. As for subclinical hyperthyroidism evidence is conclusive only with respect to an up to 5.2-fold elevated risk for atrial fibrillation. The cardiovascular risk profile of overt hypothyroidism is characterized mainly by risk factors of atherosclerosis such as hypercholesterolemia and hypertension, but also by possible development of heart failure. In contrast, data on such parameters are inconsistent for subclinical hypothyroidism. Although many of these cardiovascular alterations may hypothetically worsen prognosis, results from cohort and retrospective studies do not consistently point towards increased mortality. Only for overt hyperthyroidism an up to 1.7 fold elevated risk for cardiovascular diseases and up to 1.7 fold increased cardiovascular mortality rates have been demonstrated. However, the evidence for similarly increased cardiovascular morbidity and mortality rates in subclinical hyperthyroidism and hypothyroidism is inconclusive, and the evidence is non-existent for overt hypothyroidism. Further randomized clinical studies and population-based cohort-studies are required and should consider major cardiovascular risk factors and adverse cardiovascular events and mortality.