Vitamin D Deficiency and Hashimoto's Thyroiditis in Children and Adolescents: a Critical Vitamin D Level for This Association?

Objective: Vitamin D has been suggested to be active as an immunomodulator in autoimmune diseases such as Hashimoto's thyroiditis (HT). The goal of the present study was to investigate the vitamin D status in HT patients. Methods: This prevalence case-control study was conducted on 90 patients with HT (of ages 12.32 +/- 2.87 years) and 79 age-matched healthy controls (11.85 +/- 2.28 years). Serum 25-hydroxyvitamin D3 [25(OH)D3] levels were measured in all 169 subjects. Results: The prevalence of vitamin D deficiency in HT patients (64 of 90; 71.1%) was significantly higher than that in the control group (41 of 79; 51.9%) (p=0.025). Mean serum 25(OH)D3 level in the HT group was significantly lower compared to the control group (16.67 +/- 11.65 vs. 20.99 +/- 9.86 ng/mL, p=0.001). HT was observed 2.28 times more frequently in individuals with 25(OH) D3 levels <20 ng/mL (OR: 2.28, CI: 1.21-4.3). Conclusion: Vitamin D deficiency is associated with HT in children and adolescents. Levels lower than 20 ng/mL seem to be critical. The mechanism for this association is not clear.