Low-T3 Syndrome

TLDR

Low‑T3 state has been linked to poorer outcomes in cardiac disease patients. The study aimed to evaluate how thyroid hormone levels influence prognosis in patients with heart disease. A prospective cohort of 573 cardiac patients was stratified by free T3 levels (<3.1 pmol/L vs ≥3.1 pmol/L) and followed for cumulative and cardiac death events. During one year, low‑T3 patients had markedly higher cumulative (14.4% vs 3%) and cardiac (7.5% vs 1.5%) death rates, and free T3 emerged as the strongest independent predictor of mortality (HR 3.58 cumulative, HR 0.40 logistic), confirming low‑T3 syndrome as a potent prognostic marker in heart disease.

Abstract

Background— Clinical and experimental data have suggested a potential negative impact of low-T3 state on the prognosis of cardiac diseases. The aim of the present prospective study was to assess the role of thyroid hormones in the prognosis of patient population with heart disease. Methods and Results— A total of 573 consecutive cardiac patients underwent thyroid function profile evaluation. They were divided in two subgroups: group I, 173 patients with low T3, ie, with free T3 (fT3) &lt;3.1 pmol/L, and group II, 400 patients with normal fT3 (≥3.1 pmol/L). We considered cumulative and cardiac death events. During the 1-year follow-up, there were 25 cumulative deaths in group I and 12 in group II (14.4% versus 3%, P &lt;0.0001); cardiac deaths were 13 in group I and 6 in group II (7.5% versus 1.5%, P =0.0006). According to the Cox model, fT3 was the most important predictor of cumulative death (hazard ratio [HR] 3.582, P &lt;0.0001), followed by dyslipidemia (HR 2.955, P =0.023), age (HR 1.051, P &lt;0.005), and left ventricular ejection fraction (HR 1.037, P =0.006). At the logistic multivariate analysis, fT3 was the highest independent predictor of death (HR 0.395, P =0.003). A prevalence of low fT3 levels was found in patients with NYHA class III-IV illness compared with patients with NYHA class I-II (χ 2 5.65, P =0.019). Conclusions— Low-T3 syndrome is a strong predictor of death in cardiac patients and might be directly implicated in the poor prognosis of cardiac patients.