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.
Phase:
Phase 4
Details
Lead Sponsor:
University of California, Los Angeles
Collaborators:
Children's Hospital Los Angeles Loma Linda University National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)