Study Background and Disease Burden
Chronic critical illness (CCI) represents a protracted state of organ dysfunction and dependence on intensive care therapies, often following acute critical illness episodes. Despite intensive management, CCI is associated with high morbidity and mortality, posing a significant challenge in critical care medicine. An evolving body of evidence implicates thyroid hormone abnormalities, particularly the nonthyroidal illness syndrome (NTIS), in CCI pathophysiology. NTIS, characterized by altered thyroid hormone metabolism without intrinsic thyroid disease, is frequently observed in critically ill patients and has been linked to adverse outcomes. However, the long-term prognostic implications of thyroid hormone alterations specifically in CCI remain underexplored. Establishing reliable prognostic biomarkers is crucial to identify patients at risk for poor outcomes and optimize clinical interventions.