Thyroid gland and the heart. Pathophysiological background, diagnostic and therapeutic consequences

Irregularities in thyroid-specific laboratory parameters are frequent in the general population. Observational studies have shown associations between dysfunction of the thyroid gland and cardiovascular morbidity and mortality. The aim of this review is to give a critical overview of the relationship and treatment recommendations for the simultaneous occurrence of functional disorders of the thyroid gland and the heart. Literature searches were conducted in PubMed and Medline. Overt and also to a lesser extent subclinical hyperthyroidism are of relevance for cardiovascular mortality and morbidity, even though interventional studies are missing. Therefore, basic thyroid diagnostics are recommended when cardiovascular diseases occur or deteriorate. Whereas overt hyperthyroidism and hypothyroidism are treated immediately, subclinical thyroid dysfunction disorders require confirmation by laboratory testing. In cases with confirmed subclinical hyperthyroidism and heart disease, a thyroid-specific treatment is meaningful (e.aEuro<overline>g. with radioiodine). At what point a subclinical hypothyroidism should be treated is controversial. We usually initiate substitution treatment with levothyroxine only in patients with a thyroid-stimulating hormone (TSH) levelaEuro<overline>> 10aEuro<overline>mIU/l. A control of baseline thyroid parameters is necessary prior to initiation of any treatment with amiodarone or with deterioration of the general condition.