Thyroid gland and heart: a cardiologist’s view on an endocrinological pathology. Review

Abstract

The review of the literature considered the mechanism of action and the role of thyroid hormones (TH) on cardiovascular hemodynamics and, subsequently, on changes in the myocardial structure. A brief description of the genomic and non‑genomic mechanisms of thyroid hormones is provided. The mechanisms of thyroid hormones’ effects on the development of arterial and pulmonary hypertension, atrial fibrillation are highlighted. Attention is focused on the fact that congestive heart failure of the dilatation type develops against the background of hyperthyroidism. A possible connection between thyroid hyperfunction and Takotsubo stress‑induced cardiomyopathy was investigated. The impact of subclinical hyperthyroidism on the development and progression of cardiac pathology is illustrated. The mechanism of influence of hypothyroidism on the parameters of the lipid spectrum, acute phase proteins, insulin sensitivity, but not only the contractile function of the myocardium was considered. Changes in the electrical activity of the heart and its structural and functional changes were determined. Attention is focused on the importance of achieving euthyroidism in both hyperthyroidism and hypothyroidism. Stress‑induced Takotsubo cardiomyopathy is closely related to the hyperthyroid state and is often accompanied by the development of cardiogenic shock. Hyperthyroidism is associated with an increased risk of permanent atrial fibrillation and hypercoagulability. The achievement of euthyroid state can result in the reversal of left ventricular hypertrophy and decrease in the heart chamber dilatation. Even subclinical hyperthyroidism increases the risks of overall mortality and cardiovascular events, especially in the elderly persons. Patients with hypothyroidism are characterized by the development of anemia, dyslipidemia, decreased sensitivity to insulin, which is associated with endothelial dysfunction. In hypothyroidism, in contrast to hyperthyroidism, the risk of atrial fibrillation development is lower due to an increase in the arrhythmogenic threshold, but more typical disorders include sinus bradycardia, atrioventricular blocks of various degrees and prolongation of the QT interval, which are associated with the early development of impaired myocardial relaxation. For patients with thyroid pathology, the achievement of euthyroidism is mandatory to ensure cardio‑ and vasoprotection.