Fibromyalgia (FM) is a syndrome characterised by chronic musculoskeletal pain, tenderness and other somatic symptoms. The prevalence of FM is approximately 2-7% in the general global population and is 30-40% in the population of Hashimoto thyroiditis (HT) with a structural pathology. In 2010, new classification criteria for FM were proposed, as an alternative to the American College of Rheumatology (ACR) 1990 criteria. The objectives of the present study were to identify the prevalence of FM in the HT population and evaluate the associated features by using the new diagnostic criteria. The study group included 79 consecutive patients with HT with or without FM. Recorded data included age, gender, laboratory parameters, sociodemographic features and clinical findings, presence of somatic symptoms, and disease activity indices. The prevalence of FM in patients with HT was 62%. Antithyroid peroxidase antibody (TPOAb) positivity, duration of disease, and waist circumference were significantly associated with concomitant FM (p = 0.000, p = 0.000, and p = 0.015, respectively). A strong positive correlation was noted between fibromyalgia impact questionnaire (FIQ) scores and disease duration, age, values of thyroid-stimulating hormone (TSH) and TPOAb, waist circumference and marital status. TPOAb was found to be independent of body mass index, age and TSH. Concomitant FM is a common clinical problem in HT and its recognition is important for the optimal management of the disease. The new set of diagnostic criteria for FM reinforces this situation. Consideration of the FM component in the management of HT increases the likelihood of treatment success.
Keywords: Fibromyalgia; New diagnostic criteria; Thyroid autoimmunity.