Serum creatinine, urea, ionogram, uric acid, calcium, phosphorus, magnesium, and bone alcaline phosphatase will be assessed using standard methods. PTH will be measured by immuno-chemiluminescence using a second-generation assay (Immulite 2000; Siemens Medical Solutions Diagnostics, Los Angels, CA). Vitamin D [25(OH)D and 1,25(OH)2D] will be measured with radioimmunoassay provided by IDS (Boldon, UK).