RF35 | PSAT257 The Severity of Subacute Thyroiditis Depends on Its Causative Agent

We retrospectively evaluated 402 patients referred to of the University Hospital of Pisa because of a SAT from January 2011 to December 2020. Neck pain was present in all patients; in 92 patients it was bilateral. A previous symptomatic involvement of the upper airways was reported by 97 patients. 32 patients did not receive pharmacological treatments, 16 were treated with non-steroidal anti-inflammatory drugs (NSAIDs) and 354 with glucocorticoids; the most common initial dose of prednisone was 25 mg (in 286 patients); the majority (n. 277 patients) were treated for 90 days. 88 patients experienced permanent hypothyroidism. Free thyroxine (FT4) values ​​correlated with those of the C reactive protein (CRP), erythrocyte sedimentation rate (ESR) and thyroglobulin (Tg) ​​(p <0.001 for all). Tg values ​​correlated with the severity of thyrotoxicosis and the levels of inflammatory markers. Values ​​of FT4, Tg, ESR and CRP in patients experiencing hypothyroidism were higher compared to those observed in patients who remained euthyroid after SAT. Values ​​of FT4, Tg, and CRP and incidence of hypothyroidism were higher in patients with bilateral neck pain compared to those experiencing unilateral neck pain. Similar differences were observed comparing patients who had respiratory symptoms prior to SAT to those who did not. Glucocorticoid treatment was associated with a shorter duration of neck pain (14 days) compared to those treated with NSAIDs (28 days) and those left untreated (28 days) (p <0.001). The initial dose of 25 mg (lower than that recommended by the recent guidelines of the American Thyroid Association - 40 mg/day) was sufficient to control the pain. The annual incidence of SAT was similar throughout the entire period of observation. The third quarter of the year was characterized by the highest number of cases compared to the other quarters in all years except 2012 and 2015, when there was a higher incidence in the first quarter, and in 2020, when most of the SAT cases occurred in the second and fourth quarters. In these peculiar periods thyrotoxicosis and inflammatory markers were higher and permanent hypothyroidism more common. The clusters of SAT in 2020 occurred within a month of the Covid-19 waves, while in the winter seasons 2011-12 and 2014-15 in Italy there was a higher incidence of the influenza virus A.H3N2. In conclusion, the severity of SAT depends upon the causative virus. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 1:06 p.m. - 1:11 p.m.