In other studies, the fT4 levels were not significantly changed (18, 19, 21-23, 25, 27, 28, 31) Some studies also found increased levels of anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies in COVID-19 patients (24, 28). The gene discussed is TG; the disease is COVID-19.