Bone Abstracts

Background and methods: A specific skeletal complication in children with CKD is growth impairment. The effects of recombinant human growth hormone (rhGH) therapy on bone turnover and bone material quality are not well understood. Bone matrix mineralization density distribution (BMDD) as assessed by quantitative backscattered electron microscopy (qBEI) is an important determinant of bone material quality and reflects bone turnover (average tissue age) and mineralization kinetics of the individual bone packets of the sample.

We have recently evaluated the BMDD in cancellous and cortical bone in paired transiliac biopsies (before/after one year rhGH) in short children on dialysis (AJKD in press) and in the present study we extended the cohort to 20 pediatric patients (CKD stage 4: n=2; end-stage renal disease treated by dialysis: n=18). Bone histomorphometry was performed and all biopsies were classified according to the new TMV system.

Results: Prior treatment, strong associations between the mean bone matrix mineralization and bone turnover were found: bone matrix mineralization was higher while BFR/BS was lower compared to reference data.

After rhGH-treatment, the mean height acquisition was about 8.5 cm, serum ALP levels and bone turnover indices were significantly increased compared to baseline, and bone matrix mineralization in cancellous and cortical compartments was decreased towards normal range. A striking exception was the case of an adolescent with difficulties to adhere to therapy, who developed severe hyperparathyroidism and osteitis fibrosa concomitantly with abnormally low bone matrix mineralization.

Conclusion: Our data show that bone turnover rate is a strong predictor of the BMDD in young patients with CKD and growth deficiency. At baseline, our cohort had low bone turnover and, increased bone matrix mineralization, indicating further normal mineralization kinetics in these patients with CKD. The data suggest that rhGH treatment in children with CKD does not only increase height but also bone turnover, which appears beneficial for bone matrix mineralization.