Meta-analysis links higher FT3 and TgAb to permanent hypothyroidism after subacute thyroiditis

BackgroundSubacute thyroiditis (SAT) is a self-limiting thyroid inflammatory disorder, but some patients develop permanent hypothyroidism, impacting long-term health. We aimed to systematically synthesize evidence on factors associated with permanent hypothyroidism after SAT.MethodsA systematic search of PubMed, Embase, the Cochrane Library and Web of Science was conducted up to August 2025. Randomized trials, cohort, and case-control studies evaluating predictors of permanent hypothyroidism after SAT were included. Data were extracted following PRISMA guidelines, and study quality was assessed using the Newcastle–Ottawa Scale (NOS). Random-effects models were preferentially applied given expected clinical heterogeneity, with heterogeneity quantified using I2 and τ2.ResultsTen studies involving 1294 patients were included. Higher free triiodothyronine (FT3) levels (mean difference = 1.85, 95% CI: 0.60–3.09; Z = 2.91, P = 0.004; I² = 0%) and positive thyroglobulin antibodies (TgAb) (OR = 2.57, 95% CI: 1.35–4.88, P = 0.004; I² = 57%, τ² = 0.13) were significantly associated with an increased risk of permanent hypothyroidism after SAT. Corticosteroid therapy was associated with a lower odds of permanent hypothyroidism compared with NSAID-based management (OR = 0.40, 95% CI: 0.23–0.70, P = 0.001; I² = 36%).ConclusionsFT3, TgAb positivity and treatment modality are associated with the risk of permanent hypothyroidism following SAT. Compared with NSAID-based management, corticosteroid therapy is associated with lower odds of developing permanent hypothyroidism. These findings support early identification of high-risk patients and personalized follow-up strategies.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/, identifier CRD420251064643.