Vitamin B12 and Vitamin D Levels in Patients with Autoimmune Hypothyroidism and Their Correlation with Anti-Thyroid Peroxidase Antibodies

Background: This study was designed to investigate the vitamin D (vit-D) and vitamin B12 (vit-B12) levels and their correlation with anti-thyroid peroxidase (anti-TPO) antibodies in patients with autoimmune hypothyroidism. Methods: A total of 130 patients diagnosed with autoimmune hypothyroidism were included in the study retrospectively. The patients were divided into two groups as those having vit-B12 levels below 200 pg/mL (n = 60) and vit-B12 levels equal to or above 200 pg/mL (n = 70). These two groups were compared in terms of age, sex, thyroid-stimulating hormone (TSH), free-T4 (FT4), vit-D, and anti-TPO. The correlation between vit-B12 and anti-TPO levels was also investigated in these groups. Patients were then divided into four groups according to their vit-D levels. Patients with normal vit-D levels (25[OH]D >30 ng/mL; n = 5), those with vit-D insufficiency (20-30 mg/mL; n = 9), those with vit-D deficiency (10-20 ng/mL; n = 43), and those with severe vit-D deficiency (<10 ng/mL; n = 73). These four groups were compared in terms of age, gender, TSH, FT4, vit-B12, and anti-TPO levels. In addition, the correlation between levels of vit-D and anti-TPO was also investigated. Results: We found that vit-B12 deficiency and vit-D deficiency were associated with autoimmune hypothyroidism, and that there was a negative correlation between vit-B12 and vit-D levels and anti-TPO antibodies in these patients. Conclusion: In patients with autoimmune hypothyroidism, vit-D and vit-B12 deficiency should be investigated at the time of diagnosis and periodically on follow-ups.