Effects of vitamin D on thyroid autoimmunity markers in Hashimoto’s thyroiditis: systematic review and meta-analysis

Objective To perform a meta-analysis of randomized controlled trials to evaluate the efficacy of vitamin D supplementation on thyroid autoimmunity markers in Hashimoto’s thyroiditis (HT). Methods This meta-analysis included randomized controlled clinical trials identified by a systematic search of electronic databases (PubMed®, MEDLINE®, EMBASE, The Cochrane Library, China National Knowledge Infrastructure) from inception to August 2020. All studies included patients with HT that received vitamin D supplementation irrespective of the doses administered or the duration of treatment. The primary and secondary outcome measures were thyroid peroxidase antibody (TPOAb) and/or thyroglobulin antibody (TGAb) titres. Results Eight studies ( n = 652) were included. There was significant heterogeneity between the studies. Using a random-effect model, vitamin D supplementation reduced TPOAb titre (standardized mean difference [SMD]: –1.11; 95% confidence interval [CI]: 1–1.92, –0.29) and TGAb titre (SMD: –1.12; 95% CI: –1.96, –0.28). A subgroup analysis demonstrated that vitamin D supplementation for >3 months resulted in a decrease in TPOAb titre (SMD: –1.66, 95% CI: –2.91, –0.41) but treatment ≤3 months was ineffective. Treatment with vitamin D 3 decreased TPOAb titre (SMD: –1.48; 95% CI: –2.53, –0.42) whereas vitamin D did not. Conclusion These data suggest that vitamin D reduces autoantibody titre in patients with HT.