Thyroid Dysfunction in COVID-19 Patients: A Study at Imam Reza Hospital, Sirjan

Abstract

Background: SARS-CoV-2 affects multiple organ systems, including the thyroid gland, but the mechanisms and clinical impact remain incompletely understood. Objectives: The present study aimed to determine the prevalence and patterns of thyroid dysfunction and its association with inflammation in hospitalized COVID-19 patients. Methods: In this retrospective cohort study conducted between March and September 2021 at Imam Reza Hospital, Sirjan, Kerman province, Iran, we enrolled 167 consecutive adult COVID-19 patients. The sample size provided > 80% power to detect a 15% difference in thyroid stimulating hormone (TSH) abnormalities (α = 0.05). Thyroid hormones [total triiodothyronine (TT3), TSH, total thyroxine (TT4)] were measured by ELISA and C-reactive protein (CRP) on admission. Continuous variables are expressed as mean ± standard deviation (SD) or median (IQR); categorical variables as counts (%). Group comparisons used Kruskal-Wallis and Wilcoxon rank-sum tests; Spearman’s rank correlation assessed associations. Results: Overall, 36.5% of patients exhibited thyroid abnormalities: Low TSH (17.96%), high TSH (5.4%), low TT3 (1.8%), high TT3 (1.8%), low TT4 (6.0%), and high TT4 (3.6%). Disease severity correlated significantly with TSH and TT3 (P < 0.05), and TT4 differed by gender (P = 0.0249). The CRP correlated with disease severity (P = 0.003) and with thyroid markers [TSH rank correlation coefficient (rho) = -0.205, TT4 rho = -0.083, TT3 rho = -0.178]. Conclusions: COVID-19 is associated with a non-thyroidal illness syndrome (NTIS) pattern, notably reduced TSH and TT3 in severe cases while TT4 remains stable. Limitations include single-center design, absence of non-COVID controls, lack of free thyroxine (FT4) measurement, and no post-discharge follow-up. We recommend routine thyroid monitoring in hospitalized COVID-19 patients.