Thyroid Dysfunction in Relation to Immune Profile, Disease Status, and Outcome in 191 Patients with COVID-19

J Clin Endocrinol Metab. 2021 Jan 23;106(2):e926-e935. doi: 10.1210/clinem/dgaa813.


Objective: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related thyroiditis is increasingly recognized. The role of thyroid autoimmunity and SARS-CoV-2 viral load in SARS-CoV-2-related thyroid dysfunction is unclear. We evaluated the thyroid function of a cohort of coronavirus disease 2019 (COVID-19) patients, in relation to their clinical features, and biochemical, immunological, and inflammatory markers.

Methods: Consecutive adult patients, without known thyroid disorders, admitted to Queen Mary Hospital for COVID-19 from July 21 to August 21, 2020, were included. Serum levels of thyroid-stimulating hormone (TSH), free thyroxine, free triiodothyronine (fT3), and antithyroid antibodies were measured on admission.

Results: Among 191 patients with COVID-19 (mean age 53.5 ± 17.2 years; 51.8% male), 84.3% were mild, 12.6% were moderate, and 3.1% were severe. Abnormal thyroid function was seen in 13.1%. Ten patients had isolated low TSH, suggestive of subclinical thyrotoxicosis due to thyroiditis, although the contribution of autoimmunity was likely in 2 of them. Autoimmune thyroiditis probably also contributed to subclinical hypothyroidism in another patient. Ten patients had isolated low fT3, likely representing nonthyroidal illness syndrome. Lower SARS-Cov-2 polymerase chain reaction cycle threshold values and elevated C-reactive protein were independently associated with occurrence of low TSH (P = .030) and low fT3 (P = .007), respectively. A decreasing trend of fT3 with increasing COVID-19 severity (P = .032) was found. Patients with low fT3 had more adverse COVID-19-related outcomes.

Conclusion: Around 15% of patients with mild to moderate COVID-19 had thyroid dysfunction. There may be a direct effect of SARS-CoV-2 on thyroid function, potentially leading to exacerbation of pre-existing autoimmune thyroid disease. Low fT3, associated with systemic inflammation, may have a prognostic significance.

Keywords: COVID-19; SARS-CoV-2; euthyroid sick syndromes; thyroid function tests; thyroid gland; thyroiditis.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • COVID-19 / complications
  • COVID-19 / diagnosis*
  • COVID-19 / epidemiology
  • COVID-19 / immunology
  • Cohort Studies
  • Euthyroid Sick Syndromes / complications
  • Euthyroid Sick Syndromes / diagnosis
  • Euthyroid Sick Syndromes / epidemiology
  • Euthyroid Sick Syndromes / immunology
  • Female
  • Humans
  • Immune System / physiology*
  • Immune System / physiopathology
  • Male
  • Middle Aged
  • Prognosis
  • SARS-CoV-2 / physiology
  • Severity of Illness Index
  • Thyroid Diseases / complications
  • Thyroid Diseases / diagnosis*
  • Thyroid Diseases / epidemiology
  • Thyroid Diseases / immunology*
  • Thyroid Function Tests
  • Thyroid Gland / physiology
  • Thyroiditis, Autoimmune / complications
  • Thyroiditis, Autoimmune / diagnosis
  • Thyroiditis, Autoimmune / epidemiology
  • Thyrotoxicosis / complications
  • Thyrotoxicosis / diagnosis
  • Thyrotoxicosis / epidemiology
  • Thyrotoxicosis / immunology