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Bone turnover in children with vitamin D deficiency rickets before and during treatment
G I Baroncelli1, S Bertelloni, C Ceccarelli
1Department of Reproductive Medicine and Pediatrics, University of Pisa, Italy.
Insights
Children with vitamin D deficiency rickets exhibit elevated bone turnover, indicated by specific biochemical markers. Alkaline phosphatase is identified as the most reliable marker for diagnosis and monitoring during treatment.
Area of Science:
- Pediatrics
- Endocrinology
- Biochemistry
Background:
- Vitamin D deficiency rickets is a condition affecting bone metabolism in children.
- Assessing bone turnover requires reliable biochemical markers for diagnosis and monitoring treatment efficacy.
Purpose of the Study:
- To evaluate biochemical markers of bone formation and resorption in children with vitamin D deficiency rickets.
- To compare these markers with those in healthy children and assess changes during vitamin D treatment.
Main Methods:
- Measured serum levels of alkaline phosphatase, osteocalcin, and carboxyterminal propeptide of type I procollagen (PICP).
- Measured serum levels of cross-linked carboxyterminal telopeptide of type I collagen (ICTP) and urinary excretion of cross-linked N-telopeptides of type I collagen (NTX).
- Compared marker levels in 14 children with rickets to 44 healthy controls before and during vitamin D therapy.
Main Results:
- Children with rickets showed significantly higher alkaline phosphatase, PICP, ICTP, and urinary NTX, and lower osteocalcin compared to controls before treatment.
- During vitamin D treatment, alkaline phosphatase decreased, while osteocalcin, PICP, ICTP, and NTX transiently increased before declining.
- Marker levels normalized towards control ranges during skeletal lesion healing.
Conclusions:
- Children with vitamin D deficiency rickets have increased bone turnover both before and in the early stages of treatment.
- Alkaline phosphatase is a more dependable marker than osteocalcin, PICP, ICTP, and NTX for diagnosing and monitoring vitamin D deficiency rickets.
Unlabelled:
Biochemical markers of bone formation [alkaline phosphatase, osteocalcin, and carboxyterminal propeptide of type I procollagen (PICP)] and bone resorption [cross-linked carboxyterminal telopeptide of type I collagen (ICTP) and 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 longitudinally during vitamin D treatment (3000-4000 IU/daily). Forty-four healthy children aged 8-10.5 mo were enrolled as sex- and age-matched controls. Before treatment, serum levels of alkaline phosphatase, PICP, and ICTP, and urinary excretion values of NTX were significantly higher, and serum osteocalcin levels significantly lower than controls (31.4 +/- 3.5 microkat/L and 9.8 +/- 2.9 microkat/L, p < 0.001; 1025 +/- 89 microg/L and 952 +/- 97.4 microg/L, p < 0.02; 15.6 +/- 2.6 microg/L and 14.2 +/- 1.3 microg/L, p < 0.01; 370.7 +/- 109.4 nmol BCE and 201.8 +/- 69.2 nmol BCE, p < 0.001: 17.6 +/- 9.1 microg/L and 22.5 +/- 7.6 microg/L, p < 0.05, respectively). During treatment, serum alkaline phosphatase levels progressively declined in association with the radiographic healing of the skeletal lesions. Serum levels of osteocalcin, PICP, and ICTP, and urinary excretion values of NTX showed a transient but 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 thereafter. They were within the mean +/- 2 SD of controls before the recovery of the 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.