Incidence of subacute thyroiditis increased in South Korea during COVID-19 pandemic
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An increase in cases of subacute thyroiditis in South Korea was observed during the first year of the COVID-19 pandemic, according to a study published in Thyroid.
In an analysis of data from the Korean National Health Insurance Service and the Korea Disease Control and Prevention Agency databases, incidence of subacute thyroiditis was higher in 2020 compared with 2017 to 2019, even though incidence of respiratory viral diseases with the exception of COVID-19 declined in 2020.
“Since subacute thyroiditis-related viral infections markedly decreased in 2020, the increased subacute thyroiditis incidence in 2020 could be associated with COVID-19,” Sun Wook Cho, MD, PhD, clinical professor in the department of internal medicine at Seoul National University Hospital in South Korea, and colleagues wrote. “Additionally, subacute thyroiditis can be the initial presentation of COVID- 19; therefore, diagnostic tests for COVID-19 should be considered in patients with subacute thyroiditis during the COVID-19 pandemic.”
Researchers conducted a retrospective cross-sectional study using health insurance claims data from the National Health Insurance Service database from 2017 to 2020. Annual incidence of respiratory viral infections was obtained from the Korean Disease Control and Prevention Agency database. Subacute thyroiditis incidence from 2017 to 2019 was compared with data from 2020. Age, sex, time of subacute thyroiditis and COVID-19 diagnoses, levothyroxine use, prescription rate and duration of corticosteroid use were collected.
There were 15,447 subacute thyroiditis cases from 2017 to 2020. The annual incidence rate of subacute thyroiditis in 2020 was 8.3 per 100,000 people, higher than the rates of 7.04 per 100,000 in 2017, 6.98 per 100,000 in 2018 and 7.78 per 100,000 in 2019 (P < .001). The higher subacute thyroiditis rate in 2019 compared with the prior 2 years may have been due to an unusual peak of influenza from March to May of that year as well as an increase in parainfluenza infections from July to September 2019, according to researchers. However, in 2020, the incidence rate of all respiratory viral diseases except for COVID-19 declined compared with 2017 to 2019.
The largest increase in subacute thyroiditis incidence in 2020 came in adults aged 30 to 39 years, followed by adults aged 60 to 69 years. Women had a higher incidence rate in 2020 compared with 2017 (14 per 100,000 vs. 12.1 per 100,000; P < .001), but no difference was observed among men.
Among adults with subacute thyroiditis, a higher proportion used corticosteroids in 2020 compared with 2017 to 2019 (72% vs. 58%; P < .001). A higher proportion of those with subacute thyroiditis in 2020 had a corticosteroid prescription exceeding 1 month compared with those diagnosed in 2017 to 2019 (45% vs. 40%; P < .01). The rate of those with subacute thyroiditis using levothyroxine therapy in 2020 was similar to that in 2017 to 2019.
Fifteen people had confirmed subacute thyroiditis and COVID-19 in 2020. Of those, 11 had subacute thyroiditis after COVID-19, and 10 were diagnosed within 30 days of testing positive for COVID-19. Of those with both subacute thyroiditis and COVID-19, 86.7% were prescribed steroids for a mean of 60.9 days, and 26.7% were prescribed levothyroxine for a mean of 351 days.
“Among 4,263 subacute thyroiditis cases in 2020, 15 (0.35%) were molecularly confirmed to coincide with COVID-19,” the researchers wrote. “This was a much smaller number than expected since the annual incidence of subacute thyroiditis was significantly increased in 2020, even though the incidence of all other subacute thyroiditis-related viral infections except for COVID-19 was markedly decreased. Currently, we cannot clearly explain whether the increased subacute thyroiditis incidence in 2020 was related to the COVID-19 pandemic.”
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