The Effect of COVID-19 Infection on Thyroid Function Test in a Sample of Iraqi population
محمود شاكر خضير
Authors : Mahmood shakir Khudhair , Ali Al-Araji, Gelal Altaai
The aims of this study were to 1) assess the changes in thyroid function test in patients admitted with COVID-19 and 2) study the association of thyroid function test abnormalities and the severity of COVID-19. Methods: This is a cross-sectional study carried out at Al-Imamain Al-Kadhimain Medical City/Baghdad from December 2021 to April 2022. One hundred ninety-three patients with confirmed COVID-19 infection by PCR and CT scan of the chest were tested for thyroid function parameters. Patients were classified into 2 groups, severe and nonsevere groups, for comparison. In addition to thyroid function test, data on inflammatory biomarkers including lactate dehydrogenase, D-dimer, serum ferritin, and C-reactive protein were collected in this study Results: The prevalence of patients with abnormal thyroid function was 43 (22%) in our center. Thirty-four (17%) of patients without preexisting thyroid disease were found to have an abnormal thyroid parameter. No statistically significant association between thyroid function parameters (TSH, TT3, and TT4) and severity of the disease was found. No statistical correlation was found regarding thyroid function parameters and inflammatory biomarkers except for lactate dehydrogenase level and TT3 (R ¼ 0.5, P < .001), T4 (R ¼ 0.3, P ¼ .03) levels. Discussion/Conclusion: In our study, 79% show lower than normal TSH, 86% also show low TT3, while TT4 was normal in 56% of cases. The most probable explanation of these findings is nonthyroidal illness syndrome. In our study we were unable to exclude exogenous steroid administration, which is a factor influencing the secretion of TSH. Second, elevated proinflammatory cytokines such as IL-6 are known to mediate a similar effect. A third explanation may be a direct cytopathic effect of SARS-CoV-2 on thyroid cells. Regarding the association with the disease severity, the levels of TSH, TT3, and TT4 were lower in the severe group than the nonsevere group, suggesting a negative correlation between the parameters, but the difference was not statistically significant as was shown. Concerning proinflammatory markers and the severity of COVID-19, we found that CRP, LDH, and serum ferritin are significantly correlated with the severity of the disease but not for Ddimer levels. The findings are limited in their generalizability due to the study’s single-center, cross-sectional methodology and small sample size. Most patients with COVID-19 have euthyroid status. Most patients with abnormal thyroid function have mildly low TSH, mildly low TT3, and normal TT4, a finding consistent with nonthyroidal illness syndrome.

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