Background The association between chronic inflammatory diseases and thyroid dysfunction is well recognized. This fact can be attributed to hormonal factors and the presence of a facilitator genetic terrain. Increased prevalence of Hashimoto’s thyroiditis (HT) has been described in rheumatoid arthritis, sjögren’s syndrome and systemic lupus erythematosus1. However, there are few data on the association of this disease in other chronic rheumatic disorders such as spondyloarthritis (SpA).
Objectives To assess the prevalence of HT in a group of patients with SpA.
Methods We included in this study 62 consecutive patients with SpA and 61 age-matched controls with osteoarthritis, primary osteoporosis or fibromyalgia. From January 2012 until January 2013, blood samples were drawn in all subjects. Thyroid-stimulating hormone, free triiodothyronine, free thyroxine, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), titers of antithyroglobulin (anti-TG) and antithyroid peroxidase (anti-TPO) antibodies were measured. The thyroid ultrasound was performed in all patients with changes in thyroid function tests. Age, gender, disease duration and medical treatments were collected. To assessdisease activity we evaluated the DAS 28 in peripheral SpA and the BASDAI in axial SpA.
In the statistical analysis (chi-Square and student T-test for categorical and continuous variables, respectively), a significant association was considered if p<0.05.
Results We found thyroid dysfunction in 12.9% of SpA and in 3.3% of controls (p<0.05). Hypothyroidism was more common than hyperthyroidism in both groups. We found anti-TG or anti-TPO positive in 16.1% of SpA and in 6.6% of controls (p=0.05) and the anti-TPO was the most frequent in both groups.
The prevalence of HT (antibody positivity and ultrasonographic changes suggestive of thyroiditis) was higher in patients with SpA than in controls (9.7% vs 1.6% respectively, p<0.05). Among patients with SpA, HT was significantly more frequent in patients with peripheral involvement (83.3%) than in those with axial involvement (16.7%) and in patients with disease duration >5 years (p<0.05). Furthermore, patients treated with biologic therapy and those who were treated with ≥2 conventional DMARDs (in association) had significantly more HT (p<0.05).
There was no association between subtype of SpA, actual ESR or CRP, the current DAS28 or BASDAI.
Conclusions Our study demonstrates that HT occurs in patients with SpA with a higher prevalence than in controls, similarly as described in other chronic rheumatic diseases. Although we did not find association between HT with the current disease activity, the HT was significantly more frequent in patients with peripheral involvement, long disease duration and those treated with biological agents or with highest number of DMARDs. This suggests a possible relationship between HT and the maintenance of the inflammatory process in patients with SpA.
These results suggest that thyroid function tests should be part of the clinical evaluation in patients with SpA.
Currently, there is no clear explanation for the coexistence of these two diseases therefore further studies are needed to clarify the etiology of this association.
Chan T, Al-Saffar Z, Bucknall C. Thyroid disease in systemic lupus erythematosus and rheumatoid arthritis. Rheumatology 2001;40:353-4.
Disclosure of Interest None Declared
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