Objective: To detect and quantify the association between fibromyalgia (FM) and thyroid autoimmunity.
Methods: This cross-sectional study comprised 146 women with FM and 74 case-controls, all 18 years of age or older. FM was diagnosed according to the American College of Rheumatology 1990 classification criteria. The Mini-International Neuropsychiatric Interview (MINI) was applied for the diagnosis of depression, previously considered as an important confounding factor. Thyroid autoimmunity was defined as the occurrence of detectable antithyroid peroxidase antibodies and/or antithyroglobulin antibodies by the immunometric assay. Cases of diffuse connective tissue diseases and thyroid dysfunctions (hypo or hyperthyroidism) were excluded in both groups.
Results: Univariate analysis detected an association between FM and thyroid autoimmunity (odds ratio, OR = 3.87, 95% confidence interval, CI = 1.54-10.13), depression (OR = 3.94, 95% CI = 1.97-7.93), and age (OR = 1.04, 95% CI = 1.01-1.07). In the final logistic regression model, after adjustment for depression and age, the association between FM and thyroid autoimmunity was strengthened (OR = 4.52, 95% CI = 1.86-11.0).
Conclusion: Our results suggest an association between FM and thyroid autoimmunity.