Serum levels of thyrotropin (TSH) and total triiodothyronine (T3) are significantly lower in individuals with coronavirus disease 2019 (COVID-19), according to results of a retrospective study published in Thyroid.
Much is still not known about COVID-19, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including its effects on thyroid function.
To investigate the effect of COVID-19 on thyroid function, data from 50 patients with laboratory-confirmed COVID-19 were analyzed. Individuals admitted to the First Affiliated Hospital at Zhejiang University in Hangzhou, China, between January and March 2020 who had no history of thyroid disease and who underwent thyroid function testing during the course of COVID-19 and after recovery were included. Data from these individuals were compared with 2 control groups: healthy individuals who underwent routine physical checkups and patients with pneumonia with a similar degree of disease severity who did not have COVID-19.
Levels of TSH that were lower than the normal range were observed in 56% of the patients with COVID-19 and levels of TSH and total T3 were significantly lower in patients with COVID-19 compared with both control groups. Severity of COVID-19 significantly correlated with lower TSH and total T3 levels (P <.001). Total thyroxine (T4) levels were not significantly associated with COVID-19 status. After recovery, no significant differences in TSH, total T3, T4, or free T3 levels were observed between individuals with COVID-19 and the control groups.
Overall, the results indicated that there may be a unique effect of COVID-19 on TSH-secreting cells. This effect may be accomplished by a direct viral effect on the pituitary cells or through indirect systemic changes such as the activation of various proinflammatory cytokines, chronic stress from hypoxemia, and glucocorticoid treatment.
Limitations to this study included the inability to assess free T3, free T4, and some pituitary hormones at the time of admission due to a lack of data. Measurements of thyroid hormones were taken while most patients were undergoing glucocorticoid treatment, which may have affected the pituitary-endocrine axis feedback loops. In addition, patients with mild COVID-19 lacked thyroid function data and thus could not be analyzed.
Chen M, Zhou W, Xu W. Thyroid function analysis in 50 patients with COVID-19: a retrospective study [published online June 29, 2020]. Thyroid. doi:10.1089/thy.2020.0363