25 Hydroxyvitamin D Deficiency and Its Relationship to Autoimmune Thyroid Disease in the Elderly

Background: Low 25(OH) vitamin D levels have been associated with several autoimmune diseases and recently with autoimmune thyroiditis (AT). The aim of the study was to investigate the association of AT with low 25(OH) vitamin D levels in the elderly. Methods: One hundred sixty-eight elderly subjects (mean age: 81.6 ± 9.4 years) were enrolled. Serum levels of 25(OH) vitamin D, anti-thyroid peroxidase (TPO-Ab), anti-thyroglobulin (TG-Ab) antibodies, free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone (TSH) were measured. Results: The prevalence of AT was significantly higher in subjects with vitamin D deficiency (25(OH) vitamin D < 20 ng/mL) when compared with subjects with normal 25(OH) vitamin D (25(OH) vitamin D ≥ 20 ng/mL) levels (28% vs. 8%, respectively, p = 0.002). Patients with AT and vitamin D deficiency had a comparable hormonal profile compared to patients with AT and vitamin D sufficiency in terms of TSH (p = 0.39), FT3 (p = 0.30), FT4 (p = 0.31), TG-Ab (0.44) and TPO-Ab (0.35). Interestingly, a significant correlation between 25(OH) vitamin D and TPO-Ab (r = −0.27, p = 0.03) and FT3 (r = 0.35, p = 0.006) has been found in subjects with AT while no correlation was found between 25(OH) vitamin D levels and TG-Ab (r = −0.15, p = 0.25), TSH (r = −0.014, p = 0.09) and FT4 (r = 0.13, p = 0.32). Conclusions: These findings suggest that vitamin D deficiency was significantly associated with AT in the elderly. Therefore, the screening for AT should be suggested in subjects with vitamin D deficiency