The Role of Vitamin D in Autoimmune Thyroid Diseases: From Immunomodulation to Clinical Implications

Vitamin D plays a significant role in immune regulation and is linked to autoimmune thyroid diseases like Hashimoto’s thyroiditis (HT) and Graves’ disease (GD). While vitamin D supplementation can reduce thyroid autoantibody levels in HT, its effects on thyroid function and disease progression are inconsistent. Studies often have small sample sizes, typically fewer than 60 participants, and varying supplementation regimens, complicating definitive conclusions. Vitamin D deficiency is seen as a risk marker rather than a therapeutic target, and supplementation should be based on established indications. Further research, particularly larger and genotype-stratified trials, is needed to clarify vitamin D's clinical impact on these diseases.