Muscle-specific deletion of the vitamin D receptor in mice is associated with diaphragm muscle weakness.

Diseases or conditions where diaphragm muscle (DIAm) function is impaired, including chronic obstructive pulmonary disease, cachexia, asthma, and aging, are associated with an increased risk of pulmonary symptoms, longer duration of hospitalizations, and increasing requirements for mechanical ventilation. Vitamin D deficiency is associated with proximal muscle weakness that resolves following therapy with vitamin D. Skeletal muscle expresses the vitamin D receptor (VDR), which responds to the active form of vitamin D, 1,25-dihydroxyvitamin D by altering gene expression in target cells.

Hyperphosphatemia with elevated serum PTH and FGF23, reduced 1,25(OH)D and normal FGF7 concentrations characterize patients with CKD.

Background: Hyperphosphatemia confers adverse cardiovascular outcomes, and commonly occurs in late-stage CKD. Fibroblast growth factor 7 (FGF7) is a phosphaturic peptide which decreases renal phosphate transport in vitro and in vivo. Serum FGF7 concentrations are reduced in hyperphosphatemic patients with hypophosphatasia and are elevated in some hypophosphatemic patients with tumor-induced osteomalacia.

Chemical Characterization and Quantification of Circulating Intact PTH and PTH Fragments by High-Resolution Mass Spectrometry in Chronic Renal Failure.

Background: The precise concentrations of full-length parathyroid hormone (PTH1-84) and the identity and concentrations of PTH fragments in patients with various stages of chronic renal failure are unknown.

Methods: We developed a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method to characterize and quantify PTH1-84 and PTH fragments in serum of 221 patients with progressive renal dysfunction. Following capture by matrix-bound amino-terminal or carboxyl-terminal region-specific antibodies and elution from matrix, PTH1-84 and PTH fragments were identified and quantitated using LC-HRMS.