Congestive Heart Failure and Thyroid Dysfunction: The Role of the Low T3 Syndrome and Therapeutic Aspects.

BACKGROUND: Both the morbidity and mortality rates from congestive heart failure (CHF) remain elevated despite the medical and non-medical management of the disease, thus suggesting the existence of residual risk factors such as thyroid dysfunction. Particularly, the 15-30% of patients with CHF, especially those with severe ventricular dysfunction, display the so-called low T3 syndrome (LT3S), which seems to negatively affect the cardiovascular prognosis. OBJECTIVE: Only a few clinical trials have been carried out to verify both the safety and the efficacy of thyroid replacement in the LT3S, aiming to ameliorate the prognosis of CHF, and most of the results were controversial. METHODS: Since the aim of the present review was to briefly overview both the indication and contraindication of triiodothyronine replacement in CHF and LT3S, the authors searched PubMed using the medical subject headings (MeSH) related to the following terms: "congestive heart failure" and "low T3 syndrome" or "euthyroid sick syndrome" or "non-thyroidal sick syndrome". The research study only focused on the narrative and systematic reviews, randomized clinical trials and meta-analysis studies which were conducted before June 2019. RESULTS: Studies conducted in both animal models and humans provided controversial information about the effectiveness and safety of the T3 replacement for improving ventricular dysfunction, particularly in the long-term. CONCLUSION: Further clinical trials are needed to better explore the role of LT3S in patients with CHF and its consequent therapeutic strategy in this clinical setting.