Is thyroid autoimmunity a predisposing factor for fibromyalgia? A systematic review and meta-analysis

Objective. Studies report that autoimmune thyroid disease and elevated levels of thyroid autoantibodies are associated with fibromyalgia and widespread chronic pain. The aim of this meta-analysis was to investigate the relationship between fibromyalgia and thyroid autoimmunity. Clinical symptoms and depression associated with fibromyalgia were also investigated in relation to the presence of thyroid autoantibodies. Methods. A literature search was conducted on PubMed and Embase for studies published between January, 1980 and February, 2020 on thyroid autoimmunity in fibromyalgia patients. Two reviewers independently screened and assessed the quality of the articles. Meta-analysis was performed to analyse the difference in frequency of thyroid autoantibody positivity between fibromyalgia patients and healthy controls. Clinical symptoms and depression were also analysed according to the presence of thyroid autoantibodies. Results. Data from 10 original studies were included in the systematic review, and 5 case-control studies that satisfied the selection criteria were subjected to meta-analysis. Thyroid autoantibody positivity was more common in fibromyalgia patients compared to healthy controls (thyroid peroxidase antibody: OR 3.41, 95% CI 1.97–5.90; thyroglobulin antibody: OR 2.23, 95% CI 1.23–4.01). The frequency of postmenopausal status was significantly higher in fibromyalgia patients with thyroid autoantibodies (OR 1.95, 95% CI 1.23–3.08). However, the severity of disease (pain and fatigue level, fibromyalgia impact questionnaire score, and disease duration) and prevalence of depression did not show a statistically significant difference according to thyroid autoantibody positivity. Conclusion. Thyroid autoimmunity should be considered in fibromyalgia patients. The percentage of women in menopause was higher in thyroid autoantibody positive fibromyalgia patients.