Relationship of vitamin D status with thyroid autoimmunity in new onset autoimmune hypothyroidism

Background: We aimed to compare serum vitamin D levels in new-onset hypothyroid patients versus controls. Furthermore, we evaluated for any association of vitamin D status with hypothyroid state and its correlation with various thyroid-related parameters.

Methodology: In this cross-sectional study, 61 new-onset hypothyroid subjects (cases) and 40 age, sex and BMI matched healthy individuals (controls) were recruited. Measurements of serum vitamin D, thyroid hormones, thyroid peroxidase antibody (TPO-Ab), parathyroid hormone (PTH), calcium and phosphorus were done for all study participants.

Results: The mean serum vitamin D in cases (22.95±8.59 ng/ml) was significantly lower than the controls (27.9±7.85 ng/ml) (p<0.01). The prevalence of vitamin D deficiency was significantly higher among hypothyroid subjects than in controls (p=0.009). Hypothyroid subjects in the vitamin D deficiency group had significantly higher TSH levels, greater thyroid volume and elevated anti-TPO titres than those with vitamin D sufficiency. Serum vitamin D levels had a significant inverse correlation with anti-TPO-Ab titers even after adjustment for age, sex and BMI.

Conclusion: Serum vitamin D is significantly low in new-onset hypothyroid patients than in healthy controls. Hypothyroid patients with vitamin D deficiency have significantly higher TSH, antibody titres and thyroid volume. A significant negative correlation was observed between serum vitamin D levels and anti-TPO titres. Moreover, serum vitamin D remained an independent predictor of TPO level among hypothyroid subjects.