Thyroid dysfunction in COVID-19 patients

"Non thyroidal illness syndrome" (NTIS) or "euthyroid sick syndrome" (ESS) is a possible biochemical finding in euthyroid patients with severe diseases. It is characterized by a reduction of serum T₃ (fT3), sometimes followed by reduction of serum T₄ (fT4). The relationship between thyroid hormones levels and mortality is well known and different studies showed a direct association between NTIS and mortality. The sudden spread of the 2019 novel coronavirus (SARS-CoV 2) infection (COVID-19) and its high mortality become a world healthcare problem. Our aim in this paper was to investigate if patients affected by COVID-19 presented NTIS and the relationship between thyroid function and severity of this infection.

We evaluated the thyroid function in two different groups of consecutive patients affected by COVID-19 with respect to a control group of euthyroid patients. Group A included patients hospitalized for COVID-19 pneumonia while patients requiring intensive care unit (ICU) for acute respiratory syndrome formed the group B. Group C identified the control group of euthyroid patients.

Patients from group A and group B showed a statistically significant reduction in fT3 and TSH compared to group C. In group B, compared to group A, a further statistically significant reduction of fT3 and TSH was found.

COVID-19 in-patients can present NTIS. FT3 and TSH serum levels are lower in patients with more severe symptoms.