Thyroid Dysfunction and Inflammatory Biomarkers as Prognostic Indicators of Mortality in Hospitalized COVID-19 Patients: A Retrospective Observational Study

Background: Coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, is a systemic disease with significant endocrine implications, particularly affecting thyroid function.Non-thyroidal illness syndrome (NTIS) is frequently observed in critically ill COVID-19 patients; however, its prognostic relevance and association with systemic inflammation remain unclear.Objective: This study evaluates the relationship between thyroid dysfunction, inflammatory biomarkers, and clinical outcomes in hospitalized COVID-19 patients, aiming to determine the prognostic significance of thyroid hormone alterations in disease severity and mortality.Materials and methods: A retrospective observational study was conducted on 60 hospitalized COVID-19 patients at AIIMS Raipur, India, between August and December 2020.Thyroid function markers (TSH, FT3) and inflammatory biomarkers [hsCRP, lactate dehydrogenase (LDH), ferritin, IL-6] were analyzed.Correlation analysis, logistic regression, and receiver operating characteristic (ROC) curve analysis were performed to assess their predictive value for mortality risk.Results: Non-thyroidal illness syndrome was significantly more prevalent in deceased patients (40%) than in recovered patients (13.33%) (p = 0.001).Deceased individuals had lower Free T3 (FT3) (1.73 0.51 pg/mL vs 2.076 0.67 pg/mL, p = 0.030) and higher TSH (2.37 8.20 IU/L vs 1.35 1.13 IU/L, p = 0.006).Elevated inflammatory biomarkers (IL-6, ferritin, LDH) were associated with mortality (p < 0.05).Free T3 showed an inverse correlation with ferritin (r = -0.430,p < 0.001) and LDH (r = -0.425,p = 0.001).Receiver operating characteristic analysis identified LDH as the strongest mortality predictor (AUC = 0.843, p < 0.001), followed by TSH (AUC = 0.709, p = 0.005).Neutrophil counts were also significantly higher in deceased patients (p = 0.003).Conclusion: Thyroid dysfunction, particularly NTIS, is strongly linked to systemic inflammation and mortality in COVID-19.Free T3 and TSH may serve as valuable prognostic biomarkers.Routine thyroid function assessment alongside inflammatory markers could enhance early risk stratification and inform patient management.Further research is needed to explore potential therapeutic benefits of thyroid hormone modulation in severe COVID-19 cases.