Effects of vitamin D replacement therapy on serum FGF23 concentrations in vitamin D-deficient women in short term

ObjectiveFibroblast growth factor 23 (FGF23), a phosphatonin, inhibits renal phosphate reabsorption and suppresses 1-α hydroxylase activity. Calcitriol stimulates FGF23 synthesis in bone. We aimed to determine the effect of vitamin D replacement therapy on serum FGF23 concentrations in vitamin D-deficient women and to compare the FGF23 concentrations of vitamin D-deficient patients with healthy subjects and patients with genetically determined hypophosphatemic rachitis.Design and methodsThe study group was composed of vitamin D-deficient females (n=18, mean age 29.1±9.9 years), vitamin D-sufficient healthy females (control group; n=19, mean age 28.5±5.2 years), and patients with genetically determined hypophosphatemic rachitis (n=13, mean age 26.5±15.1 years). The groups were compared for serum FGF23, 1,25-dihydroxyvitamin D3 (1,25(OH)2D), calcium, phosphate, bone turnover markers, intact parathyroid hormone (PTH), and urinary excretion of calcium and phosphate. The vitamin D-deficient group was re-evaluated after a standard treatment regimen.ResultsSerum FGF23 concentrations were significantly lower in vitamin D-deficient patients than in vitamin D-sufficient women and hypophosphatemic rachitis group. Serum FGF23 and phosphate concentrations further decreased significantly during replacement of vitamin D (P