High prevalence of anti-TSH receptor antibody in fibromyalgia syndrome

Aim: Fibromyalgia syndrome (FMS) is defined as chronic widespread pain that cannot be accounted for by any other medical disorder. Our aim was to explore the prevalence of thyroid autoimmunity in patients with FMS. Methods: For determining thyroid function in 207 FMS patients, we tested for the titers of free tri-iodothyronine, free thyroxine, thyroid-stimulating hormone (TSH), anti-thyroid peroxidase antibody (TPOAb), anti-thyroglobulin antibody (TgAb) and anti-TSH receptor antibody (TRAb). Results: Twenty-five patients who had either subclinical hyper-or hypothyroidism, or overt hypothyroidism were excluded. Sixty-nine FMS patients with autoimmune thyroid diseases (AITD) (37.9%, 69/182) were identified. The prevalence of positivity for TRAb, TgAb and TPOAb was 20.3% (n = 37), 16.5% (n = 30) and 13.2% (n = 24), respectively. Compared to control populations in previous studies, the prevalence of TRAb positivity was high, and titers of TRAb were low (1.0-1.5 IU/L). The prevalence of TPOAb and TgAb positivity was not significantly higher than that reported in FMS patients in previous studies. Clinical symptom profiles were identical for FMS patients with and without AITD. Conclusion: We found a high prevalence of AITD among 207 patients with clinically defined FMS, with TRAb being especially prominent among these patients. Further study is needed to evaluate changes in thyroid function among FMS patients with AITD.