Bone Abstracts

Objectives: Patients with osteogenesis imperfecta (OI) type IA have a mild phenotype with normal or near-normal height. The addition of recombinant human GH (rhGH) to ongoing treatment with bisphosphonates can increase measures of BMD and growth. We studied growth rate bone density and bone metabolism in two girls affected by OI type IA and growth delay.

Materials and methods: Eight children (six girls and two boys) with OI type IA were treated with Risedronate. Among them two girls with mean age 6.5 years old presented growth delay. These girls were treated with rhGH at a dose 0.35 mg/kg per week for 4 years or more. Auxologic data were measured every 3 months, bone age was determined at the start and at every 6 months. At every 3 months IGFI, osteocalcin, alkalinphosphatase, calcium and phosphorus blood levels, and urinary hydroxyproline and calcium levels were determined. Bone mineral density (BMD) measurements were made at the start and repeated at 12, 24, 36, and 48 months at the lumbar spine and whole body by DXA.

Results: After 48 months, linear growth velocity increased from 4.5 to 8 cm/year in the first year, to 8.5 cm/year in the second, to 9.5 cm/year in the third year, and 5 cm/year in the fourth. DXA–BMD at lumbar spine increased significantly from 0.359 to 0.464 g/cm² (+29%) in the first year to 0.505 g/cm² (+9%) in the second and to 0.585 g/cm² (+15%) in the third and 0.649 g/cm² (+10%) in the fourth year. Whole body:BMD improved+36% in the first year, 4.4% in the second year, 9.5% in the third, and 16% in the fourth year. Serum osteocalcin levels increased significantly after rhGH treatment.

Conclusion: rhGH treatment addition at bisphosphonates in OI type IA increases significantly the rate of linear growth velocity. The bone turnover increases, and BMD in lumbar spine and whole body increase also. The fractures did not increase. More children shoud be treated with rhGH to see the long-term benefits of this treatment in final adult height and quality of bone in OI.