Endocrine Abstracts

Context: Graves’ disease (GD) is the most common cause of hyperthyroidism. It occurs more commonly amongst women, smokers and patients with other autoimmune diseases or a family history of thyroid autoimmunity. Peak incidence occurs between 40 and 60 years of age but any age group may be affected. Vitamin D deficiency has been reported to link with a variety of autoimmune diseases. However, the relationship between the thyroid autoimmunity in GD and vitamin D deficiency is unclear.

Objective: We aimed to investigate the association of vitamin D and TSH receptor antibody levels (TRab) with GD.

Design and setting: This was a cross-sectional study conducted in education and research hospital. A total of 67 patients with GD (30 men and 37 women) along with 53 age-matched non-GD controls participated in the study.

Main outcome measures: TSH, free triodothyronine (FT₃), free thyroxine (FT₄), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb), thyrotrophin receptor antibody (TRAb), parathyroid hormone (PTH), calcium, and 25-hydroxyvitamin D (25(OH)D) levels were measured.

Results: 25(OH)D levels were significantly lower in the GD group, compared with non-GD control group (P<0.001). 25(OH)D levels was inversely correlated with TRab levels (r=−0.38, P<0.001). However, our results did not show a correlation between the levels of 25(OH)D and the levels TPOAb, TGAb, FT₃, FT₄, and TSH. The levels of PTH in serum were increased in TRAb positive GD patients compared to control subjects (P<0.001). Logistic regression analysis results indicated that 25(OH)D levels were not a significant risk factor for developing GD.

Conclusion: In patients with GD, low vitamin D status might be cause of increased titres of TRAb, suggesting a possible link between vitamin D status and increased thyroid autoimmunity in GD.