Renal hypophosphatemic rickets. Growth and mineral metabolism after treatment with calcitriol (1,25-dihydroxyvitamin D3) and phosphate supplementation.

To delineate the mineral metabolism of renal hypophosphatemic rickets and to update progress in linear growth after calcitriol (1,25-dihydroxyvitamin D3) therapy, the medical records of 19 patients were examined retrospectively from January 1978 through December 1985. With a mean (+/- SD) follow-up period of 42.0 +/- 5.4 months after calcitriol had been administered for at least 12 months, the growth measurements were as follows: the percentile weight (mean +/- SD) remained unchanged, with the initial being 12.3% +/- 17.3% and the final being 15.3% +/- 18.6%, and the length/height percentiles were -2.7% +/- 5.9% and -2.4% +/- 4.4%. The growth velocity index showed a significant improvement from mean values of 61.7% (at age 2 years) to mean values of 101.2% (at age 11.2 years). Serum phosphate concentrations rose from the initial value of 2.9 +/- 0.6 to 3.5 +/- 0.8 mg/dL (0.9 +/- 0.2 to 1.1 +/- 0.3 mmol/L). The effects of calcitriol on renal function were tested by creatinine clearance values, which were 127 +/- 22 mL/min/1.73 m2 (2.12 +/- 0.37 mL/s/1.73 m2) at the conclusion of the study, compared with 128 +/- 25 mL/min/1.73 m2 (2.13 +/- 0.41 mL/s/1.73 m2) obtained at the initiation of calcitriol therapy. We conclude that calcitriol treatment of renal hypophosphatemic rickets in children results in improvement of growth velocity and serum phosphate concentration without deterioration of renal function.