Thyroid Hormone Profile and Its Prognostic Impact on the Coronavirus Disease 2019 in Korean Patients

BACKGROUND: Data on the association between coronavirus disease 2019 (COVID-19) and thyroid have been reported, including overt thyrotoxicosis and suppression of thyroid function. We aimed to evaluate the thyroid hormone profile and its association with the prognosis of COVID-19 in Korean patients. METHODS: The clinical data of 119 patients with COVID-19, admitted in the Myongji Hospital, Goyang, South Korea, were retrospectively evaluated. The thyroid hormone profiles were analyzed and compared based on disease severity (non-severe disease vs. severe to critical disease). Clinical outcomes were analyzed according to the tertiles of thyroid hormones. RESULTS: Of the 119 patients, 76 (63.9%) were euthyroid, and none presented with overt thyroid dysfunction. Non-thyroidal illness syndrome was the most common manifestation (18.5%), followed by subclinical thyrotoxicosis (14.3%) among patients with thyroid dysfunction. Thyroid stimulating hormone (TSH) and triiodothyronine (T3) levels were significantly lower in patients with severe to critical disease than in those with non-severe disease (P<0.05). Patients in the lowest T3 tertile (<0.77 ng/mL) had higher rates of mechanical ventilation, intensive care unit admission, and death than those in the middle and highest (>1.00 ng/mL) T3 tertiles (P<0.05). COVID-19 patients in the lowest T3 tertile were independently associated with mortality (hazard ratio, 5.27; 95% confidence interval, 1.09 to 25.32; P=0.038) compared with those in the highest T3 tertile. CONCLUSION: Thyroid dysfunction is common in COVID-19 patients. Changes in serum TSH and T3 levels may be important markers of disease severity in COVID-19. Decreased T3 levels may have a prognostic significance in COVID-19 related outcome.