How Bone is Made in Children Receiving Dialysis
How Bone is Made in Children Receiving Dialysis
The study outlined is designed to measure and to determine whether the combined use of
 vitamin D2 (ergocalciferoI) and 1-alpha-hydroxyvitamin D2 (doxercalciferol)) or
 doxercalciferol alone will correct the mineralization defect in pediatric patients with
 established secondary hyperparathyroidism (2°HPT) undergoing regular peritoneal dialysis.
 Serum phosphorus levels will be controlled with a calcium¬-free-metal free phosphate binder;
 (obtained at baseline and after 8 months of treatment) sevelamer. Indices of bone
 mineralization obtained at baseline and after 8 months of treatment will be measured by
 quantitative histomorphometry in iliac crest bone biopsies after double tetracycline
 labeling. Immunohistochemistry will be done in specimens of bone biopsies from iliac crest to
 examine the expression for selected markers of bone turnover and mineralization such as
 FGF-23, DMP1, MEPE and OPG. Serum PTH levels will be measured with the 1st and 2nd generation
 immunometric assay (PTH-IMAs) and fibroblast growth factor-23 (FGF-23) will be determined by
 one assay with specific detection antibodies that are against epitopes within the C-terminus
 of FGF-23 and another assay that uses antibodies against epitopes within the N- and
 C-terminal portions of the molecule respectively. The value of non-invasive assessment of
 bone mass by quantitative computed tomography (QCT) and its relationship with vascular
 disease determined by ultrasound (US) of intimal carotid thickness (CIMT) will be correlated
 with bone histomorphometry and the different biochemical determinations.
Inclusion Criteria:

 -  medically stable patients

 -  6-21 years old

 -  undergoing treatment with continuous cycling peritoneal dialysis

 -  evidence of mineralization defect and secondary hyperparathyroidism

 Exclusion Criteria:

 -  histopathological lesion of bone such as adynamic bone or osteomalacia

 -  poor compliance

 -  current treatment with prednisone or other immunosuppressives

 -  treatment with human recombinant growth hormone

 -  parathyroidectomy