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


METHODS
The 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.


RESULTS
Serum 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<0.05). A significant negative correlation was evident between FGF23 and PTH before vitamin D replacement in the patients (r=-0.469, P<0.05).


CONCLUSIONS
Decreased FGF23 concentrations, which further decline during vitamin D replacement therapy, may have favorable action on bone mineralization by counterregulatory effect on phosphate homeostasis. Lower 1,25(OH)2D concentrations at baseline and hypophosphatemia during treatment may have dominating effects on FGF23 concentrations in vitamin D deficiency, leading to decreased FGF23 concentrations at baseline and during replacement therapy.
Uzum
Ayse Kubat
AK
Division of Endocrinology and Metabolism, Department of Internal Medicine, Istanbul Faculty of Medicine, University of Istanbul, Istanbul 34390, Turkey. akubatuzum@yahoo.com
Salman
Serpil
S
Telci
Aysegul
A
Boztepe
Harika
H
Tanakol
Refik
R
Alagol
Faruk
F
Ozbey
Nese Colak
NC
D000328:Adult; D015415:Biomarkers / Q000097:blood; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D013997:Time Factors; D014807:Vitamin D / Q000097:blood / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000188:drug therapy*; D055815:Young Adult
D015415:Biomarkers; C000717427:FGF23 protein, human; D014807:Vitamin D; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23