Bone turnover in children with vitamin D deficiency rickets before and during treatment

Biochemical markers of bone formation [alkaline phosphatase, osteocalcin, a nd carboxyterminal propeptide of type I procollagen (PICP)] and bone resorp tion [cross-linked carboxyterminal telopeptide of type I collagen (ICTP) an d cross-linked N-telopeptides of type I collagen (NTX)] were measured in 14 children aged 8.5-10.5 mo with vitamin D deficiency rickets before and lon gitudinally during vitamin D treatment (3000-4000 IU/daily). Forty-four hea lthy children aged 8-10.5 mo were enrolled as sex- and age-matched controls . Before treatment, serum levels of alkaline phosphatase, PICP, and ICTP, a nd urinary excretion values of NTX were significantly higher, and serum ost eocalcin levels significantly lower than controls (31.4 +/- 3.5 mu kat/L an d 9.8 +/- 2.9 mu kat/L, p < 0.001; 1025 +/- 89 mu g/L and 952 +/- 97.4 mu g /L, p < 0.02; 15.6 +/- 2.6 mu g/L and 14.2 +/- 1.3 mu g/L, p < 0.01; 370.7 +/- 109.4 nmol BCE and 201.8 +/- 69.2 nmol BCE, p < 0.001; 17.6 +/- 9.1 mu g/L and 22.5 +/- 7.6 mu g/L, p < 0.05, respectively). During treatment, ser um alkaline phosphatase levels progressively declined in association with t he radiographic healing of the skeletal lesions. Serum levels of osteocalci n, PICP, and ICTP, and urinary excretion values of NTX showed a transient b ut significant (p < 0.05 to p < 0.001) increase in comparison with baseline values during the first 2-4 wk of treatment, and decreased slowly thereaft er. They were within the mean +/- 2 SD of controls before the recovery of t he skeletal lesions. Conclusions: These findings suggest that children with vitamin D deficiency rickets have increased bone turnover before and during the first weeks of treatment. Alkaline phosphatase is a more reliable marker than osteocalcin, PICP, ICTP and NTX for diagnosing and monitoring these patients.