| Outcome Measures: |
Primary: Percent Change in PTH Levels, Mean percent change in parathyroid hormone (PTH) levels will be calculated., Baseline and 9 months|Change in Bone Mineral Density (BMD) of the Femoral Neck by Dual-energy X-ray Absorptiometry (DXA), To test if 9-months of treatment with etelcalcetide changes femoral neck areal BMD, a change in age and sex adjusted Z-Score will be calculated from baseline to 9 months. A Z-Score of zero represent the population mean and higher Z-Scores indicate a better outcome., Baseline and 9 months|Propensity as Measured by T50, The propensity to calcify soft tissues will be measured by T50 for 9 months of treatment. T50 is a novel serum-based marker that assesses the propensity of calcification in serum. Shorter T50 indicates greater propensity to calcify., 9 months|Percent Change in Mean Hardness, Hardness will be measured by Ramen nano-indentation and mineralization measured by histomorphometry obtained (in GPa)., Baseline and 9 months | Secondary: Change in Bone Mineral Density (BMD) of the Spine by DXA, To test if 9-months of treatment with etelcalcetide improves spine BMD, a change in age and sex adjusted Z-Score will be calculated from baseline to 9 months. A Z-Score of zero represent the population mean and higher Z-Scores indicate a better outcome., Baseline and 9 months|Change in Bone Mineral Density (BMD) of Total Hip by DXA, To test if 9-months of treatment with etelcalcetide improves total hip BMD, the change in age and sex adjusted Z-Score will be calculated from baseline to 9 months. A Z-Score of zero represent the population mean and higher Z-Scores indicate a better outcome., Baseline and 9 months|Change in Bone Formation Rate, A quadruple label method will be used to assess effects of etelcalcetide on the bone formation rate. A tetracycline double label will be used pre-etelcalcetide and a declomycin double label will be used post-etelcalcetide in a protocol that administers label 3-days on, 12-days interlude, 3-days on. A single bone biopsy will be performed 1 to 10 days after completion of the second double label. Biopsy cores will be placed into 70% ethanol then serially dehydrated and embedded in methyl methacrylate. Four-micron thick sections will be cut and left unstained for dynamic histomorphometry. A region of interest including all trabecular bone and excluding cortical bone will be analyzed separately for each tetracycline or declomycin label. Standard analysis techniques will be used to measure single, double and no labelled surfaces and distances between the two labels of each fluorescence. Standard calculations of the bone formation rate/bone surface (um3/um2/year) will be made., Baseline and 9 months
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