STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) diagram of the study. *Cont-SAT, classic subacute thyroiditis; Cov-SAT, COVID-19–related subacute thyroiditis; Vac-SAT, SARS-CoV-2 vaccine–related subacute thyroiditis. *Patients with a follow-up period of more than 30 days and follow-up thyroid function tests available (n = 653) were analyzed for treatment evaluation and follow-up comparisons, patients with a follow-up period of 47 days or more (n = 623) were evaluated for recurrence, and all patients with a follow-up period of 180 days or more (n = 236) were evaluated for established hypothyroidism.