The Role of Vitamin D Supplementation in Managing Thyroid Disorders: A Randomized Controlled Trial

Abstract

Background: Thyroid disorders, including hypothyroidism, hyperthyroidism, and autoimmune thyroid diseases (AITDs) such as Hashimoto's thyroiditis and Graves' disease, are prevalent endocrine disorders with significant global health impacts. Emerging evidence suggests that vitamin D, known for its role in bone health and calcium metabolism, may also influence immune function and thyroid health.
Objective: This study aimed to evaluate the efficacy of vitamin D supplementation in improving thyroid function and reducing autoimmune activity in individuals with thyroid
disorders.
Methods: This double-blind, randomized controlled trial (RCT) involved 200 participants
diagnosed with thyroid disorders, including hypothyroidism, hyperthyroidism, and AITDs.
Participants were randomly assigned to receive either vitamin D supplementation (50,000
IU/week for 8 weeks, followed by 2,000 IU/day for 10 months) or a placebo for 12 months.
Primary outcomes included changes in serum 25-hydroxyvitamin D [25(OH)D] levels, thyroid function tests (TSH, Free T4, Free T3), and thyroid autoantibodies (anti-TPO, antiTG). Secondary outcomes included improvements in clinical symptoms and quality of life. Data were analyzed using SPSS version 25.0.
Results: Participants in the intervention group exhibited a significant increase in serum 25(OH)D levels (from 18.5 ± 4.3 ng/mL to 35.2 ± 6.2 ng/mL, p < 0.001). This increase was
associated with significant reductions in TSH levels (-1.2 ± 0.8 mIU/L, p < 0.001) and thyroid autoantibodies (anti-TPO: -30 ± 12 IU/mL, p < 0.001; anti-TG: -25 ± 10 IU/mL, p < 0.001). Improvements in Free T4 and Free T3 levels were also observed in the intervention group (p < 0.001). The control group showed no significant changes in these parameters. Participants in the intervention group reported greater improvement in clinical symptoms and quality of life

Conclusion: Vitamin D supplementation significantly improves thyroid function and reduces
autoimmune activity in individuals with thyroid disorders, particularly those with
hypothyroidism and AITDs. These findings suggest that vitamin D may serve as an effective
adjunctive therapy in managing thyroid disorders. Further research is needed to confirm these results and explore the long-term benefits of vitamin D supplementation in this population.