The Spectrum of Thyroid Function Tests and Autoantibodies During Hospitalization and After Six Months of Discharge in COVID-19 Patients: Does COVID-19 Trigger Autoimmunity?

Objective: The aim of the study was to investigate thyroid function test (TFT) results and anti-thyroid antibody titers in acutely infected COVID-19 patients, as well as the changes in TFT and autoantibody results during the 6-months recovery period among survivors.

Patients and design: A total of 163 adult COVID-19 patients and 124 COVID-19 survivors were evaluated in terms of TFT (thyroid stimulating hormone [TSH], free triiodothyronine [fT3], and free thyroxine [fT4]) and anti-thyroid antibodies (anti-thyroglobulin [anti-Tg] and anti-thyroid peroxidase [anti-TPO]).

Results: Thyroid dysfunction was noted in 56.4% of patients on admission, including the non-thyroidal illness syndrome (NTIS) in most cases. Presence vs. absence of thyroid dysfunction on admission was associated with significantly higher rate of severe disease (p < 0.001), while severe vs. mild-to-moderate disease was associated with significantly lower serum fT3 levels (p = 0.001). Overall, 94.4% of survivors were euthyroid at the time of 6 months post-discharge, while in some patients, the post-COVID-19 recovery period was also associated with significantly increased anti-TPO titers and the presence of new-onset or persistent subclinical hypothyroidism.

Conclusion: This is one of the few studies to evaluate TFT and autoantibodies over a 6-month period after recovery from COVID-19. The presence of emergent or persistent subclinical hypothyroidism and the significantly increased anti-TPO titers in some patients during the convalescence period suggest the need for follow-up for development of thyroid dysfunction and autoimmunity among COVID-19 survivors.