Thyroid disorders in patients with newly diagnosed rheumatoid arthritis is associated with poor initial treatment response evaluated by disease activity score in 28 joints-C-reactive protein (DAS28-CRP): An observational cohort study

To determine the prevalence of thyroid disorders among newly diagnosed rheumatoid arthritis (RA) patients and evaluate the association between clinical characteristics of RA and thyroid disorders, and also initial treatment response in the RA patients with thyroid disorders. Newly diagnosed, adult RA patients who were diagnosed according to the new 2010 American College of Rheumatology/European League Against Rheumatism criteria since January 1, 2010, were included. Patients’ demographic data, serology results including immunoglobulin M rheumatoid factor (IgM RF), anticyclic citrullinated peptide antibody (anti-CCP), and antinuclear antibody (ANA), and also disease activity score in 28 joints-C-reactive protein at the time of diagnosis and after 4 months (±1–2 months) of treatment initiation were extracted from Danish Danbio Registry. Patients’ electronic hospital records for the past 10 years were reviewed to reveal if they had been diagnosed with thyroid disorders or they had abnormal thyroid test. In all, 439 patients were included, female 60.1%, mean age 64.6 ± 15.0 years and disease duration 2.6 ± 1.7 years. Prevalence of thyroid disorders was 69/439 (15.7%) and hypothyroidism was the most frequent disorder (30.4%). The presence of thyroid disorders among RA patients was significantly associated with female sex (P < .001), ANA positivity (P = .04), and anti-CCP ≥100 EU/mL (P = .05). Furthermore, RA patients with thyroid disorders had significantly poorer initial response to RA treatment compared with patients with isolated RA after 4 months of treatment (P = .02). There were no associations between thyroid disorders and age, disease duration, and also IgM RF positivity. Presence of thyroid disorders in RA patients is suggestive of a more aggressive disease and poor outcome, with direct effect on initial treatment response. To diagnose concurrent thyroid disorders at an earlier stage, routine measurement of serum thyroid-stimulating hormone is recommended in all RA patients at the time of diagnosis and with yearly interval thereafter.