Asai K, Shirakabe A, Kiuchi K, et al. - In view of a recent assessment of low triiodothyronine (T3) syndrome as a prognostic marker of acute heart failure (AHF) has been done, and there is a lack of clarity as to adverse outcomes typically resulting from low T3 syndrome may be seen in which cases, researchers performed this investigation in 1,190 AHF patients in order to address this topic. A total of 956 patients (80.3%) with euthyroidism were classified as: the normal group (n = 445, FT3 ≥ 1.88 µIU/L) and low-FT3 group (n = 511, FT3 < 1.88 µIU/L). The low-FT3 group vs the normal group exhibited significantly lower survival rates and event-free rates within 365 days. Findings revealed the presence of low T3 as a predictor of adverse outcomes. A strong link of AHF patients with low T3 syndrome with aging and malnutrition was also revealed. In patients with AHF, adverse outcomes were likely in the presence of low T3 syndrome complicated with older age and malnutrition.