Relation between free triiodothyronine/free thyroxine ratio, echocardiographic parameters and mortality in dilated cardiomyopathy

Abstract

Background: Abnormalities in thyroid function are frequent in patients with heart failure and are associated with increased mortality. However, the relation between thyroid hormone levels and echocardiographic parameters has not been investigated sufficiently. Aim: The aims of this study were to investigate the correlations of thyroid hormone levels with echocardiographic parameters and to evaluate their associations with subsequent mortality in a group of patients with dilated cardiomyopathy (DCMP). Methods: Serum levels of thyroid hormones were measured in 111 consecutive patients with DCMP (35 female, 76 male, mean age: 62 F 12 years). All patients underwent echocardiographic examination and were followed-up for a period of 12 F 8 months. Results: Twenty-three patients (21%) had abnormalities in thyroid function tests. Free triiodothyronine (fT3)/free thyroxine (fT4) ratio was significantly correlated with most of echocardiographic parameters, such as chamber diameters and ejection fraction. Sixteen patients (14%) died during the follow-up period; their fT3/fT4 ratio was significantly lower than the patients who survived (1.31 F 0.37 vs. 2.01 F 0.72, p < 0.001). A fT3/fT4 ratio of V 1.7 was associated with an increased risk of mortality ( p < 0.001), independent of other prognostic markers. Sensitivity, specificity, positive and negative predictivity of fT3/fT4 ratio V 1.7 for cardiac mortality were 100%, 71%, 36% and 100%, respectively. Conclusion: Determination of FT3/FT4 ratio may be a valuable and simple predictor for identification of patients with DCMP who are at high risk of subsequent mortality.

Reduced expression of thyroid hormone receptors and beta-adrenergic receptors in human failing cardiomyocytes

“…Other changes in contractile proteins and regulators of sarcoplasmic calcium handling were found to be similar in heart failure and hypothyroidism [9][10][11]. In addition the echocardiographic ejection fraction and mortality was found to be significantly correlated with the serum thyrotropin concentration in dilated cardiomyopathy [23] and a low T3 syndrome, characterized by low circulating levels of the biologically active form of T3 in the presence of normal thyrotropin (TSH) and of thyroxine was reported to occur in approximately 30% of patients with advanced heart failure [12]. Serum-free T3 plasma levels in our DCM patients were significantly lower than in controls, but no subject had fT3 values lower than reference limits [12].…”

A Low-Normal Free Triiodothyronine Level Is Associated with Adverse Prognosis in Euthyroid Patients with Heart Failure Receiving Cardiac Resynchronization Therapy

“…11) Hypothyroidism and "low T3 syndrome," which represent decreased level of fT3 in common, are both the frequent comorbidities resulting to poor prognosis for patients with HF. 5,12) Our study demonstrated that even the low-normal level of fT3 (less than lower quartile) could influence the prognosis of HF patients after CRT implantation. It was an interesting result that fT3 might be a sensitive biomarker to detect the prognosis of HF patients receiving CRT.…”

The renin–angiotensin system in thyroid disorders and its role in cardiovascular and renal manifestations

“…Several factors have been implicated in low-T 3 syndrome, including: increased T 3 receptor expression, which may be responsible for maintaining euthyroidism in the face of reduced circulating thyroid hormone levels (Williams et al 1989); reduced enzyme activity of 5 0 -monodeiodinase, responsible for converting T 4 to T 3 in peripheral tissues (Mebis & Van den Berghe 2011); reduced plasma selenium concentration, a shared cofactor with antioxidant enzymes and deiodinases (Van Lente & Daher 1992); increased cytokine levels (Hermus et al 1992, Boelen et al 1995; and increased levels of Triac (T 3 analog) and/or Tetrac (T 4 analog), which may feedback to the pituitary/hypothalamus region and cause a secondary hypothyroidism (Carlin & Carlin 1993). Low-T 3 syndrome is also a strong prognostic predictor of death in patients with heart disease, giving additional information to the conventional clinical and functional cardiac parameters (Iervasi et al 2003, Kozdag et al 2005, Pingitore et al 2005.…”

“…The RAS in low-T 3 syndrome and subclinical thyroid disorders Changes in thyroid function parameters are observed in starvation and fasting, cardiac disease (Kozdag et al 2005, Pingitore et al 2005, renal disease (Lim et al 1980, Zoccali et al 2005, renal transplantation (Hekmat et al 2010), ageing (Tognini et al 2010), and increased saline intake (Cruz et al 2011), leading to low-T 3 syndrome (also known as non-thyroidal illness syndrome or euthyroid sick syndrome). This syndrome is characterized by low circulating T 3 levels and normal or decreased T 4 levels and, usually, by normal thyroid stimulating hormone (TSH) levels.…”