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 mlU/l; p = 0.01); levels were above normal range (0.4-4 mlU/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 mlU/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.