Diminished linear growth during intermittent calcitriol therapy in children undergoing CCPD

Daily calcitriol therapy has been reported to improve linear growth in children with renal bone disease, and 1,25-dihydroxyvitamin D is a key regultor of chondrocyte proliferation and differentiation. Whereas large intermittent doses of calcitriol can lower serum parathyroid hormone (PTH) levels and reverse the skeletal changes of secondary hyperparathyroidism, the impact of intermittent calcitriol therapy on linear growth in children is not known. Thus, we studied 16 pre-pubertal patients with bone biopsy-proven secondary hyperparathyroidism who completed a 12-month prospective clinical trial of intermittent calcitriol therapy. Biochemical results and growth data obtained during intermittent calcitriol therapy were compared to values determined during the preceding 12 months of daily calcitriol therapy in each study subject; changes in bone histology were assessed after one year of intermittent calcitriol therapy. Z-scores for height did not change during 12 months of daily calcitriol therapy. Although the skeletal lesions of secondary hyperparathyroidism improved in most patients, Z-scores for height decreased from -1.8 +/- 0.32 to -2.0 +/- 0.33, P < 0.01, during intermittent calcitriol therapy. The largest reductions were seen in patients who developed adynamic bone lesions after 12 months of treatment. Delta Z-scores for height correlated with serum PTH, r = 0.71, P < 0.01, and alkaline phosphatase levels, r = 0.67, P < 0.01, during intermittent calcitriol therapy but not during daily calcitriol therapy. The data suggest that high dose intermittent calcitriol therapy adversely affects linear growth, particularly in patients with the adynamic lesion. The higher doses of calcitriol or the intermittent schedule of calcitriol administration may directly inhibit chondrocyte activity within growth plate cartilage of children with end-stage renal disease.