Bone mass development and bone metabolism in juvenile idiopathic arthritis: treatment with growth hormone for 4 years

Abstract

Objective: To study the acquisition of bone mass and changes in bone mineral density (BMD) related to age, bone age, pubertal status, and growth hormone (GH) therapy in 11 children with juvenile idiopathic arthritis (JIA) longitudinally over 4 years, in comparison to healthy children.

Methods: Bone mineral content (BMC), BMD, and vertebral area were measured by dual energy x-ray absorptiometry. Since BMC and BMD increase with size, BMD was converted to volumetric BMD (vBMD) after adjustment for vertebral size.

Results: At inclusion all patients (7 female, 4 male, mean age 10.3 +/- 2.1 yrs) had low BMD, with a mean z-score for area BMD (aBMD) of -2.04 +/- 0.8 SD. After adjustment for size, vBMD was 0.198 g/cm3, and after 4 years of GH treatment it increased significantly to 0.232 g/cm3 (p < 0.03), expressed as SD scores that increased from -2.97 +/- 0.81 SD to -2.83 +/- 0.67 SD. In relation to bone age, vBMD SD increased from -2.53 +/- 0.85 to -2.41 +/- 0.79. Compared to pretreatment values, bone formation and resorption markers increased significantly during treatment.

Conclusion: Our results reflect an increase in bone turnover under GH therapy in these patients. Despite biochemical changes there was a stabilization of vBMD for age and bone age, with a percentage increase comparable to healthy children. Longterm GH treatment will be necessary to evaluate a potential positive effect of GH on bone density and metabolism in patients with JIA.