Vitamin D Deficiency as a Risk Factor in Autoimmune Thyroid Diseases: An updated Systematic Review
Keywords:
vitamin D, vitamin D metabolism, autoimmune thyroid disease, Hashimoto's autoimmune thyroiditis, Graves ' diseaseAbstract
Background and Objective: Autoimmune thyroid diseases (AITDs), including Hashimoto’s thyroiditis (HT) and Graves’ disease (GD), represent some of the most prevalent endocrine disorders worldwide. Increasing evidence suggests that vitamin D, beyond its role in calcium homeostasis, acts as an immunomodulatory hormone. Vitamin D deficiency has been implicated as a contributing factor in the pathogenesis of autoimmune disorders, including AITDs. This review systematically evaluates the current evidence on the association between vitamin D deficiency and AITDs, with emphasis on differences in serum vitamin D levels between affected individuals and healthy controls, as well as the odds of vitamin D deficiency by disease status.
Methods: This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive literature search was performed in PubMed, Scopus, Web of Science, and Google Scholar for studies published between January 2012 and December 2023. Eligible studies included randomized controlled trials, cohort studies, and case–control studies that reported serum vitamin D levels in patients with AITDs compared with healthy controls, or evaluated the odds of vitamin D deficiency by AITD status. Studies were screened for methodological rigor, inclusion criteria, and outcome measures.
Results: The evidence demonstrated heterogeneity across study designs and populations. Several studies reported significantly lower serum vitamin D levels in patients with HT or GD compared with healthy controls, suggesting a potential link between vitamin D deficiency and AITD risk. However, other studies failed to confirm this association. Differences in geographic location, sample size, baseline vitamin D status, and duration of follow-up contributed to these inconsistent findings.
Conclusion: Vitamin D deficiency may play a contributory role in the development and progression of autoimmune thyroid diseases. While current evidence supports a potential association, inconsistencies highlight the need for large-scale, multicenter randomized controlled trials to establish causality and to determine whether vitamin D supplementation could serve as a preventive or therapeutic strategy in AITDs.
