Evaluation of non-thyroidal illness syndrome in shock patients admitted to pediatric intensive care unit in a developing country

During critical illness, children my experience various changes in their thyroid hormone levels. Such changes are termed non-thyroidal illness syndrome (NTI). The extent of change correlates with the severity of the illness and its outcomes in critically ill patients. This study aimed to investigate the correlation between the severity of shock and thyroid hormone derangement. This prospective observational study included forty patients aged one month to five years who were admitted to the pediatric intensive care unit (PICU) with shock. Thyroid function tests were conducted on admission, after shock reversal, and five days later. NTI patterns were observed in 70% of patients. The PIM2 score showed a significant negative correlation with T3 (r =  - 0.353, p = 0.026) and FT3 levels on admission (r =  - 0.417, p = 0.007). Furthermore, after shock reversal, the PIM2 score continued to exhibit significant negative correlations with T4 (r =  - 0.444, p = 0.004), T3 (r =  - 0.329, p = 0.038), FT3 (r =  - 0.355, p = 0.025), and FT4 levels (r =  - 0.379, p = 0.016).    Conclusion: This study underscores the high prevalence of NTI in PICU shock patients and suggests monitoring thyroid hormone levels for outcome prediction and treatment guidance. Further research is needed to optimize NTI management in critically ill children. What is Known: • Non-thyroidal illness syndrome (NTIS) is a condition observed in critically ill patients. • There has been limited research on NTI in children, and existing studies have generated conflicting results regarding the relationship between thyroid hormones and clinical outcomes in cases of sepsis and septic shock. What is New: • The study has revealed dynamic changes in free triiodothyronine (FT3) levels during the process of shock reversal and recovery in children who experienced shock. • A significant negative correlation was found between the Pediatric Index of Mortality 2 (PIM2) score and several thyroid hormone levels, including FT3 on admission and T4, FT3, and FT4 on shock reversal.