Efficacy of two different dosages of prednisone for treatment of subacute thyroiditis: a single-center, prospective, randomized, open-label, non-inferiority trial

Background: The aim of study was to explore the efficacy and safety of low-dose (LD) and regular dose (RD) prednisone (PDN) for treatment of subacute thyroiditis (SAT).  Methods: Patients were randomly allocated using the block randomization method to the two groups. The primary outcome was the time required for PDN treatment. Secondary outcomes included percentages of relapse, mean score for the Morisky Medication Adherence Scale-8©（MMAS-8）, time required for symptoms to resolve, cumulative PDN dose (mg) and mean erythrocyte sedimentation rate (ESR) at 2 weeks and baseline.  Results: The study cohort included 77 patients, randomized 74 participants, and 68 completed the study. There was no significant difference in the treatment duration between the LD and RD groups (55.31±14.05 vs.61.25±19.95 days, p =0.053). The mean difference in the time required for PDN treatment between the LD and RD groups was -1.86 (95%CI =-10.64 to 6.92) days, which was within the non-inferiority margin of 7 days. There was a significant difference in the mean score for MMAS-8 between the LD and RD groups (5.84±0.88 vs.5.40±1.14, p =0.023). Also, there was a significant difference in the cumulative PDN dose between the LD and RD groups (504.22±236.86 vs.1002.28±309.86, p =0.046). The ESR at 2 weeks was statistically significant as compared to baseline values in both groups, with pre-treatment and post-treatment ESRs of 49.91±24.95 and 17.91±12.60/mm/h, ( p <0.0001) in the LD group and 65.08±21.77 and 17.23±13.61/mm/h ( p <0.0001) in the RD group.  Conclusion: Low-dose PDN therapy may be sufficient to achieve complete recovery and better outcomes of SAT. This study is registered with Chinese Clinical Trial Registry (02/10/2021 ChiCTR2100051762).