Some patients with moderate to severe COVID-19 disease seem to experience inflammation of the thyroid gland that is different from thyroid inflammation caused by other viruses, according to a study.

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The study was presented virtually at ENDO 2021, the Endocrine Society's annual meeting. One-third of the study participants still had signs of thyroid inflammation after three months, even though their thyroid function had normalised. The study is following patients to determine whether this inflammation will trigger permanent thyroid dysfunction.

In spring 2020, 15 per cent of the COVID-19 patients hospitalized in acute medicine units at Fondazione IRCCS Ca' Granda Policlinico Hospital of Milan in Italy had thyroid hormone alterations due to multi-factorial causes, including thyroid inflammation. In comparison, only 1 per cent of hospitalized patients during the same period in 2019 prior to the pandemic had thyroid hormone alterations.

People with thyroiditis or inflammation of the thyroid gland, triggered by other viruses usually recover thyroid function in the short term. However, there is a long-term increased risk of permanently reduced thyroid function, caused by late-onset effects of viral infection, or by the immune system attacking the thyroid gland, said lead researcher Ilaria Muller, M.D., PhD, of the University of Milan in Italy. She wanted to find out whether the thyroiditis associated with SARS-CoV-2, the virus that causes COVID-19 disease, follows the same pattern as thyroid inflammation caused by other viruses. She started a surveillance program to monitor the thyroid function of patients every three months after being hospitalized for moderate to severe COVID-19 disease. The patients undergo routine blood and ultrasound testing to monitor their thyroid function and signs of inflammation.

Muller found the thyroiditis in people with moderate to severe COVID-19 disease differs from typical thyroiditis in several ways. These include the absence of neck pain, the presence of mild thyroid dysfunction, higher frequency among men and the association with severe COVID-19 disease. So far, 53 patients have completed the evaluation at three months. All had normal thyroid function.

"After three months, patients' thyroid function has normalized, but signs of inflammation were still present in about one-third of patients", Muller said. "We are continuing to monitor these patients to see what happens during the following months. It is important to know whether SARS-CoV-2 virus has late-onset negative effects on the thyroid gland, in order to promptly diagnose, and eventually treat, the condition".