Background/Purpose:

Although the association of autoimmune thyroid dysfunction and primary Sjögren’s syndrome (SjS) is well known, it is less clear whether a similar relationship also exists between autoimmune thyroid dysfunction and ankylosing spondylitis (AS). Therefore, we aimed to define the frequency of autoimmune thyroid dysfunction in patients with AS, to find out whether the frequency was significantly different from the healthy controls.

Methods:

Eighty patients with AS (mean age: 40.57±10.13 years; M/F: 50/30) fulfilling the 1984 Modified New York Criteria and 80 healthy subjects, age and sex-matched with AS patients were included. As the positive control group, 62 female patients with primary SjS (mean age: 50.27± 10.84 years) fulfilling the diagnostic criteria of the European Consensus Group were also studied. All cases underwent thyroid ultrasonography by a single endocrinologist to evaluate the size, nodularity and homogeneity of the thyroid gland. Besides, serum free triiodothyronine (fT3), thyroxine (fT4), thyroid-stimulating hormone (TSH), and thyroid autoantibodies were measured. The diagnosis of Hashimoto’s thyroiditis was made only if the patient had thyroid autoantibody positivity plus at least one of the following criteria, namely diffuse goiter with physical examination, abnormality in thyroid function tests and ultrasonographic thyroid hypoechogenicity. Statistical analysis was performed with SPSS.15 for Windows. The chi-squared test and Fisher’s exact test, when appropriate, were used to compare cases and controls. p values < 0.05 were considered statistically significant.

Results:

The frequency of Hashimoto’s thyroiditis was significantly higher in patients with AS compared with age and sex-matched healthy controls (10% vs 1.3% p: 0.034). Similarly, the frequencies of any thyroid autoantibody positivity (13.8% vs 2.5% p: 0.017) and ultrasonographic thyroid hypoechogenicity (30% vs 11.3% p: 0.045) were also significantly higher in AS group. Other parameters such as thyroid gland volume and nodularity, and thyroid function tests did not differ significantly between AS and healthy control groups. As expected, frequencies of Hashimoto’s thyroiditis, thyroid autoantibodies and thyroid hypoechogenicity were highest in primary SjS group, however differences did not reach to statistically significant levels between the SjS and AS groups.

Conclusion:

The present study showed that the frequency of autoimmune thyroid dysfunction was significantly higher in AS group, compared with healthy controls. It should be kept in mind that, patients with AS may have concomitant autoimmune thyroid dysfunction, and in case of clinical suspicion, such patients should be further evaluated with clinical and laboratory parameters.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-prevalance-of-autoimmune-thyroid-disfunction-in-ankylosing-spondylitis/