Study of thyroid disorders in ankylosing spondylitis patients on anti-tumor necrosis factor treatment

Abstract

Abstract: BACKGROUND: Ankylosing spondylitis (AS) is a systemic rheumatic disease characterized mainly by involvement of sacroiliac joints and axial skeleton. Tumor necrosis factor-alpha (TNF-α) inhibitors are biologic agents which are Food and Drug Administration approved to treat AS and also act as a key factor in the treatment of autoimmune thyroid disease. OBJECTIVE: This study aimed to evaluate the thyroid gland disorders (functions and thyroid autoantibodies) in AS patients on anti-TNF-α biologics and their relation to disease activity. PATIENTS AND METHODS: This comparative cross-sectional study included 75 AS patients classified into two groups: Group I: treated with NSAIDs (n = 30) and Group II: treated with anti-TNF-α biologics (n = 45). Thyroid function tests, thyroid autoantibodies, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and human leukocytic antigen B27 were measured. AS disease activity was assessed by Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), and Bath Ankylosing Spondylitis Metrology Index (BASMI) scores. Thyroid ultrasonography was used to detect any thyroid gland nodularity and echogenicity. RESULTS: There were significant differences between both groups regarding BASDAI (P = 0.005), CRP (P = 0.005), thyroid-stimulating hormone (TSH) (P = 0.001), and anti-thyroid peroxidase (anti-TPO) (P = 0.007). A significant difference was found regarding the thyroid status, with more normal thyroid and more hyperthyroid patients in the anti-TNF-treated group (P = 0.003). There were statistically significant positive correlations between BASDAI and CRP (P = 0.007), TSH (P = 0.004), and thyroid anti-TPO antibody (P = 0.008) in the anti-TNF-treated patients. By ultrasound examination of the thyroid gland, 75.6% of the anti-TNF group had normal thyroid gland compared to 56.6% of the other group, and the reported nodules were mostly of benign TIRADS classification. Comparing different subgroups of thyroid nodularity with different treatment regimens revealed significant differences in BASDAI and different laboratory investigations in favor of the anti-TNF-treated patients. CONCLUSION: From this cohort study, we can conclude that thyroid autoimmune disease and thyroid nodules in AS patients can be controlled by treatment with anti-TNF-α biologic drugs better than NSAIDs alone.