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THYROID FUNCTION TESTS
How does COVID-19 affect the thyroid?
BACKGROUND
Coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2 virus infection. It had first was identified in December 2019 and caused a global pandemic that continues to affect all aspects of life all over the world. COVID-19 has a high risk of death from failure of respiratory system, but it may affect many different systems of the body.
Changes in thyroid hormone levels are common in any severe illness and called non-thyroidal illness. This occurs as a reaction to systemic stress. On the other hand, some reports described changes in thyroid function tests due to destruction of thyroid cells or inflammation in the gland. In this paper, the authors aimed to get more insight into the reasons for the changes that occur in thyroid function tests during COVID-19.
THE FULL ARTICLE TITLE
Campi I et al 2021 The spectrum of thyroid function tests during hospitalization for SARS COV-2 infection. Eur J Endocrinol 184:699–709. PMID: 33683214.
SUMMARY OF THE STUDY
The study included 144 patients hospitalized with COVID-19 and associated pneumonia at a single center in Milan, Italy between March and May 2020. There were 97 men and 47 women, ages ranging from 26 to 96. COVID-19 infection was confirmed in all patients by PCR testing.
Patients who previously had thyroid disease or who were taking drugs that can affect the thyroid were excluded. Serum TSH, free T3, free T4, thyroglobulin, thyroglobulin antibodies and markers of inflammation (CRP, IL-6 and cortisol) were measured. The death rate was 25% as 36 of 144 patients died.
Most of the patients had normal TSH, free T4 and T3 levels when they were admitted. Only 39% of patients had low TSH levels and half of these patients had low free T3 levels. Serum free T3 levels predicted the patients who were more likely to die from the disease. TSH and free T3 levels were back to normal at the time of discharge in the patients who survived. Serum thyroglobulin levels were normal and there was no sign of destruction of thyroid cells.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The authors concluded that the thyroid test abnormalities seen in COVID-19 are temporary and likely caused by the response of the immune system and not from a direct effect of the virus on the thyroid cells. Evaluation of thyroid function during hospitalization is not helpful and not recommended. However, if thyroid tests are done during admission and are abnormal, it is reasonable to monitor thyroid function after hospital discharge.
— Ebru Sulanc, MD
ATA THYROID BROCHURE LINKS
Thyroid Function Tests: https://www.thyroid.org/thyroid-function-tests/
Novel Coronavirus (COVID-19) and the Thyroid: https://www.thyroid.org/covid-19/ coronavirus-frequently-asked-questions/
ABBREVIATIONS & DEFINITIONS
Thyroxine (T4): the major hormone produced by the thyroid gland. T4 gets converted to the active hormone T3 in various tissues in the body.
Triiodothyronine (T3): the active thyroid hormone, usually produced from thyroxine.
TSH: thyroid stimulating hormone — produced by the pituitary gland that regulates thyroid function; also the best screening test to determine if the thyroid is functioning normally.
Thyroglobulin: a protein made only by thyroid cells, both normal and cancerous. When all normal thyroid tissue is destroyed after radioactive iodine therapy in patients with thyroid cancer, thyroglobulin can be used as a thyroid cancer marker in patients that do not have thyroglobulin antibodies.
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