Thyroid hormone and heart failure

Abstract

Thyroid hormone metabolic disarray has been identified as a risk factor for the progression of heart disease and the development of heart failure (HF). Both hyper- and hypothyroidism have been associated with a failing myocardium. Poor cardiac contractility and low cardiac output due to hyperthyroidism is a rare occurrence and is mostly seen in patients with preexisting heart disease. Referred to as a "rate related" phenomenon, hyperthyroid-induced sustained sinus tachycardia or atrial fibrillation may further reduce ventricular contractility. Increasingly, the hypothyroid state, and in particular a low triiodothyronine level, has been associated with a reduced cardiac performance and poor prognosis in HF, even in the presence of normal thyroid-stimulating hormone levels. Low thyroid hormone levels alter cardiac gene expression and increase systemic vascular resistance, both resulting in a reduction of cardiac contractility and cardiac output. This review summarizes current data on thyroid dysfunction and HF as well as the emerging implications of the "low triiodothyronine state."

Thyroid Disease and the Heart

“…[107][108][109] The decrease in serum T 3 is proportional to the severity of the heart disease as assessed by the New York Heart Association functional classification. 107 The low T 3 syndrome is defined as a fall in serum T 3 accompanied by normal serum T 4 and TSH levels, and the syndrome results from impaired hepatic conversion of T 4 to the biologically active hormone, T 3 , by 5Ј-monodeiodination. 6 The cardiac myocyte has no appreciable deiodinase activity and therefore relies on the plasma as the source of T 3 .…”

Thyroid Replacement Therapy and Heart Failure

“…Impairment of T4-to-T3 conversion was also found to be proportional to the clinical severity of HF as assessed by the New York Heart Association functional classification. 21,42 Furthermore, T3 levels in plasma strongly correlated with exercise capacity and oxygen consumption in HF patients. 43 In summary, clinical observations seem to indicate the presence of a close pathophysiological link between primary scHypo or impaired T4 to T3 conversion and evolution of HF.…”

Subclinical hypothyroidism is an independent predictor of adverse cardiovascular outcomes in patients with acute decompensated heart failure

“…It has been reported that low‐T3 syndrome was also observed in patients with heart failure, and that impairment of thyroxine (T4) to T3 conversion was found to be proportional to the clinical severity of heart failure 5, 6. Furthermore, it has been reported that the impaired concentration recovers to the baseline after adequate therapy for heart failure 7.…”