Bone Density Conservation Agents/therapeutic use; Bone Resorption/prevention & control; Ergocalciferols/therapeutic use; Hyperparathyroidism, Secondary/drug therapy; Kidney Failure, Chronic/physiopathology; Kidney/drug effects; Receptors, Calcitriol/agonists; Aged; Biomarkers/blood; Biomarkers/chemistry; Bone Density/drug effects; Bone Resorption/etiology; Bradykinin/blood; Bradykinin/chemistry; Complement C4/analysis; Complement C4/chemistry; Female; Humans; Hyperparathyroidism, Secondary/blood; Hyperparathyroidism, Secondary/etiology; Hyperparathyroidism, Secondary/physiopathology; Kidney/immunology; Kidney/physiopathology; Kidney Failure, Chronic/immunology; Kidney Failure, Chronic/therapy; Kidney Transplantation/immunology; Magnetic Phenomena; Male; Microspheres; Middle Aged; Peptide Fragments/blood; Peptide Fragments/chemistry; Proteomics/methods; Receptors, Calcitriol/metabolism; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization