Correlation of TSH Levels with Inflammatory Markers in COVID-19 Patients: A Retrospective Study

Background: COVID-19 caused by SARS-CoV-2 is an acute disease which may lead to severe systemic inflammation, causing multi-organ dysfunction and death. Studies indicated that thyroid-stimulating hormone (TSH) levels were lower when the infection was more severe. Methods: We conducted a retrospective study of 105 patients admitted from 2020 to 2023 to the University Clinical Centre in Katowice with a positive COVID-19 test. TSH levels, white blood cell count (WBC), platelet count (PLT), C-reactive protein (CRP), D-dimers, procalcitonin levels, lymphocyte count and percentage, and neutrophil-to-lymphocyte ratio (NLR) were evaluated. Results: The average age was 69.49 (SD 14.14) and the range was 36–95 years. A total of 53.2% of the population were male. After statistical analysis, lymphocyte count (p = 0.0038) correlated positively and NLR (p = 0.04682) correlated negatively with TSH level in COVID-19 patients, and PLT correlated positively with TSH level in the female population (p = 0.0384), while CRP (p = 0.81320), D-dimers (p = 0.974), WBC (p = 0.6862), Lymphocyte percentage (p = 0.1838), and procalcitonin (p = 0.906) did not reach statistical significance. Conclusions: TSH levels may be associated with lymphocyte count and NLR in patients with confirmed cases of SARS-CoV-2 infection, and with PLT in the female subgroup. Other evaluated inflammatory markers were not significant. These findings suggest that TSH has potential as a biomarker of disease severity, but further studies are needed to investigate this claim, and consideration should be given to other indicators of inflammation.