Increased prevalence of antithyroid antibodies and subclinical hypothyroidism in children with juvenile idiopathic arthritis.

OBJECTIVE: To estimate the occurrence of antithyroid antibodies (ATA) and hypothyroidism in children with juvenile idiopathic arthritis (JIA) compared to matched healthy controls. METHODS: The occurrence of ATA, including antithyroglobulin (anti-TG) and antithyroid peroxidase (anti-TPO) antibodies, was evaluated by quantitative immunometric ELISA in children with JIA and in a healthy matched control group. Thyroid function was assessed in both groups. RESULTS: The study group included 66 patients with JIA (50 girls, 16 boys) of mean age 11.7 +/- 4.4 years (range 2-23). The control group included 89 children (71 girls, 18 boys) of mean age 10.8 +/- 4.2 years (range 2-18). Mean age at onset of joint disease was 7.3 +/- 3.6 years (range 1-15). Anti-TG antibodies were found in 7 of 62 patients (11.3%) in the JIA group and 2 of 89 controls (2.2%) (p = 0.03); anti-TPO antibodies were found in 5 of 65 patients (7.9%) and one of 89 controls (1.1%) (p = 0.08). All patients with ATA had oligoarticular type JIA (p = 0.01). Mean thyroid stimulating hormone (TSH) levels were higher in the study group than in controls (2.6 +/- 2.3 vs 1.9 +/- 1.0 mIU/l; p = 0.01); levels were above normal range (0.4-4 mIU/l) in 8 study patients (12%) and 3 controls (3.4%) (p = 0.055). Overall, ATA were found in 9 of the 150 study participants, 4 (44%) of whom had TSH levels above 4 mIU/l (p = 0.001). CONCLUSION: Children with JIA have a higher than normal incidence of ATA and subclinical hypothyroidism and should be routinely screened for these variables.