Association between Thyroid Function and Prognosis of COVID-19: A Retrospective Observational Study.

: Coronavirus disease 2019 (COVID-19) is a severe infectious illness. It has been reported that COVID-19 has an effect on thyroid function. However, the association between thyroid function and prognosis of COVID-19 is still unclear.: This retrospective study included patients with COVID-19 admitted to Tongji Hospital in Wuhan from January 28 to April 4, 2020. Demographic, epidemiological, clinical, laboratory, treatment, and outcome data were collected from patients with laboratory-confirmed COVID-19. Patients without history of thyroid disease who had a thyroid function test at admission were enrolled in the final analysis. Risk factors of in-hospital death were explored using univariable and multivariable Cox regression analyses. Survival differences were assessed with Kaplan-Meier curves and log-rank test.: A total of 127 patients were included in this study, with 116 survivors and 11 non-survivors. The serum levels of thyroid stimulating hormone (TSH) [0.8 (0.5-1.7) . 1.9 (1.0-3.1) μIU/mL, = .031] and free triiodothyronine (FT) [2.9 (2.8-3.1) . 4.2 (3.5-4.7) pmol/L, < .001] were lower in non-survivors than in survivors, and a low FT state (defined as FT < 3.1 pmol/L) at admission accounted for a higher proportion in non-survivors than in survivors (72.7% . 11.2%, < .001). Univariate Cox regression analysis showed that FT level (HR 0.213, 95% CI: 0.101-0.451, < .001) and the low FT state (HR 14.607, 95% CI: 3.873-55.081, < .001) were negatively and positively associated with the risk of in-hospital death, respectively. Furthermore, multivariate Cox regression analysis revealed that a low FT state was associated with an increased risk of in-hospital death after adjusting for confounding factors (HR 13.288, 95% CI: 1.089-162.110, = .043). Moreover, Kaplan-Meier curves indicated a lower survival probability in COVID-19 patients with a low FT status.: Serum FT level is lower in non-survivors among moderate-to-critical patients with COVID-19, and the low FT state is associated with an increased risk of in-hospital mortality of COVID-19.