Thyroid hormone concentrations in severely or critically ill patients with COVID-19

J Endocrinol Invest. 2021 May;44(5):1031-1040. doi: 10.1007/s40618-020-01460-w. Epub 2020 Nov 2.


Objective: COVID-19 is a new coronavirus infectious disease. We aimed to study the characteristics of thyroid hormone levels in patients with COVID-19 and to explore whether thyroid hormone predicts all-cause mortality of severely or critically ill patients.

Methods: The clinical data of 100 patients with COVID-19, who were admitted to Wuhan Tongji Hospital from February 8 to March 8, 2020, were analyzed in this retrospective study. The patients were followed up for 6-41 days. Patients were grouped into non-severe illness and severe or critical illness, which included survivors and non-survivors. Multivariate Cox proportional hazards analysis was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality in association with continuous and the lower two quartiles of thyroid hormone concentrations in severely or critically ill patients.

Results: The means of free T3 (FT3) were 4.40, 3.73 and 2.76 pmol/L in non-severely ill patients, survivors and non-survivors, respectively. The lower (versus upper) two quartiles of FT3 was associated with all-cause mortality HR (95% CI) of 9.23 (2.01, 42.28). The HR (95% CI) for all-cause mortality in association with continuous FT3 concentration was 0.41 (0.21, 0.81). In the multivariate-adjusted models, free T4 (FT4), TSH and FT3/FT4 were not significantly related to all-cause mortality. Patients with FT3 less than 3.10 pmol/L had increased all-cause mortality.

Conclusion: FT3 concentration was significantly lower in patients with severe COVID-19 than in non-severely ill patients. Reduced FT3 independently predicted all-cause mortality of patients with severe COVID-19.

Keywords: COVID-19; Mortality; Nonthyroidal illness; Thyroid hormone.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • COVID-19 / blood*
  • COVID-19 / mortality
  • Cause of Death
  • China / epidemiology
  • Comorbidity
  • Critical Illness / mortality
  • Female
  • Humans
  • Male
  • Middle Aged
  • Predictive Value of Tests
  • Proportional Hazards Models
  • Retrospective Studies
  • Survival Analysis
  • Thyroid Function Tests
  • Thyroid Hormones / blood*
  • Triiodothyronine / blood


  • Thyroid Hormones
  • Triiodothyronine