Thyroid disorders in patients with psoriatic arthtritis and other rheumatic diseases

OBJECTIVE: 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 psoriatic arthtritis (PsA), ankylosing spondylitis (AS) and other spondyloarthritis group of diseases. Therefore, our aim in this study was to define the frequency of autoimmune thyroid dysfunction in patients with PsA, AS and RA and to find out whether the frequency was significantly different from the healthy controls. METHODS: We enrolled 21 patients with PsA, 26 patients with AS and 24 patients with RA. As the control group, 27 healthy subjects, age and sex-matched with RD (rheumatic disease) patients. Along with healthy controls, both PsA, AS and RA groups evaluated for autoimmune thyroid disease. In this respect, all patients underwent thyroid ultrasonography to evaluate the size, nodularity and homogenity of the thyroid gland. Besides, serum free triiodothyronine (fT3), thyroxine (fT4), thyroid-stimulating hormone (TSH), and anti-TPO (anti-thyroid peroxidase) and anti-TG (antithyroglobulin) antibodies were determined. The diagnosis of Hashimoto thyroiditis (HT) was made only if the patient had thyroid autoantibody positivity plus at least one of the following criteria, namely diffuse guatr with physical examination, abnormality in thyroid function tests and ultrasonographic thyroid hypoechogenicity. RESULTS: The frequencies of ultrasonographic thyroid hypoechogenicity and Hashimoto's thyroiditis were significantly higher in patients with AS and RA compared with age and sex-matched healthy controls. On the other hand, other parameters such as thyroid gland volume and nodularity, and thyroid function tests did not differ significantly between RA and AS groups and control groups. While frequencies of HT was higher in PsA group than healthy controls, the difference was not statistically significant. In addition there were not significantly difference between PsA and healthy controls on thyroid ultrasound findings and thyroid function tests. CONCLUSION: Our study revealed that patients with PsA, AS and RA had higher incidence of autoimmune thyroid dysfunction than the healthy controls, in consistent with the results of previous studies in the literature. Therefore, it should be kept in mind that, patients with rheumatic disease may have concomitant autoimmune thyroid dysfunction. In case of clinical suspicion, such patients should be further evaluated with clinical and laboratory parameters. However, in order to better clarify the issue of whether autoimmune thyroid dysfunction is really associated with PsA, AS and RA further prospective controlled studies with larger number of patients, as well as better elucidation of the underlying pathogenetic mechanisms for both diseases are required.