Preventive effect of prednisolone on permanent hypothyroidism in subacute thyroiditis: retrospective study of 743 cases

Purpose Permanent hypothyroidism (PH) after subacute thyroiditis (SAT) requires lifelong thyroid hormone replacement therapy. This study aimed to investigate the risk factors for PH and its association with treatment. Methods A retrospective observational study of 743 patients diagnosed with SAT from 2016 to 2019 was conducted. Results Initial treatment was prednisolone (PSL) in 332 patients (44.7%), nonsteroidal anti-inflammatory drugs (NSAIDs) in 364 (49.0%), and rest without medication in 47 (6.3%). Of the NSAID-treated patients, 238 (65.4%) switched to PSL. Final treatment was PSL in 570 (76.7%), NSAIDs in 126 (17.0%), and rest in 47 (6.3%). Permanent hypothyroidism occurred in 32 patients (4.3%). Prednisolone therapy was used less frequently in the PH group (46.9%) than in the euthyroid group (78.1%, P < .01). Multivariable logistic regression identified no PSL therapy (odds ratio [OR] 3.92, 95% confidence interval [CI] 1.88-8.24, P < .01) and male sex (OR 2.52, 95% CI 1.13-5.37, P = .03) as significant risk factors for PH. Compared with patients aged <70 years, those ≥70 years had significantly lower free triiodothyronine, free thyroxine, and C-reactive protein levels, but higher thyroid-stimulating hormone levels. The proportion of elderly patients receiving PSL therapy was lower (56.1% vs 77.9%; P < .01), and the duration of PSL therapy was shorter (P = .01). Conclusion Prednisolone therapy for SAT helps prevent PH through its anti-inflammatory effects. In younger patients, early PSL therapy may be preferable to reduce the risk of PH, as PH requires long-term levothyroxine therapy. In elderly patients, NSAIDs were often sufficient, whereas PSL therapy may be considered when clinically indicated.