Circulating Fibroblast Growth Factor-23 (FGF-23) following vitamin D supplementation in vitamin D insufficiency
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1
Guy's Hospital, Osteoporosis Clinic, Rheumatology, United Kingdom
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2
Royal Liverpool Hospital, Department of Clinical Chemistry, United Kingdom
1,25 dihydroxy vitamin D up-regulates Fibroblast Growth Factor -23 (FGF-23). Both are implicated in a feedback loop, as increases in FGF-23 inhibit 1, 25 dihydroxy vitamin D synthesis. High dose vitamin D supplements are frequently given to patients with low 25(OH) vitaminD who are at high fracture risk. We investigated the effect of high dose vitamin D on circulating FGF-23 concentrations and the interaction between FGF-23 and 1, 25 dihydroxy vitaminD in patients with vitamin D deficiency /insufficiency.
Thirty one subjects (11M aged (mean [SD]) 56.6 [19.3] and 20 F aged 62.7 [15.3] years were studied. They were administered an intra-muscular injection of 300,000 I.U of Ergocalciferol (D2) and prescribed daily supplements of calcium (1.2 g) and 800 I.U colecalciferol (D3). Blood samples were obtained at baseline, 1, 2 and 3 months for measurement of serum calcium, phosphate, PTH, 25 (OH) vitamin D and FGF-23. 1,25dihydroxyvitamin D was measured at baseline and 3 months.
Serum 25 (OH) vitamin D increased significantly (baseline mean [SD] 33.5 [14.9], 50.5 [21.6] nmol/L at 3 months (p < 0.05). PTH decreased from baseline, but not significantly (baseline: 64[60], 3 months: 50[28.5] ng/L). There was no significant difference in serum phosphate. FGF-23 concentrations increased significantly (baseline: 85.3[44.1], 1 month : 111[58], 2 month : 99.6 [62], 3 month: 108[59] RU/ml (p <0.05). A positive correlation was seen between FGF-23 and serum phosphate at 3 months (r= 0.44, p= 0.02). 1, 25 dihydroxyvitamin D increased in 18 patients (Group A : baseline 107 [39] , 3 month 134[34.5] pmol/L) and decreased in 13 patients (Group B : baseline 158.6 [40] , 3 months 123 [37] pmol/L p<0.05). Baseline 1, 25 dihydroxyvitamin D was significantly higher in Group B compared to Group A (p<0.001). There was no significant difference in PTH. A larger increase in FGF-23 was seen in Group B (Group B mean [SEM] % change from baseline; 1 month: 90[47], 2 month: 84[44], 3 month: 45[16], Group A; 1 month: 36[12.5], 2 month: 14 [10], 3 month: 29 [15] p=0.039). These data suggest that FGF-23 is a counter-regulatory hormone for 1, 25 dihydroxy vitamin D production.
Keywords:
Bones,
Bone Research
Conference:
2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society, Cambridge, United Kingdom, 27 Jun - 29 Jun, 2011.
Presentation Type:
Oral
Topic:
Abstracts
Citation:
Inaoui
R,
Fraser
W,
Fogelman
I and
Hampson
G
(2011). Circulating Fibroblast Growth Factor-23 (FGF-23) following vitamin D supplementation in vitamin D insufficiency.
Front. Endocrinol.
Conference Abstract:
2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society.
doi: 10.3389/conf.fendo.2011.02.00029
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Received:
30 Sep 2011;
Published Online:
30 Sep 2011.
*
Correspondence:
Dr. R Inaoui, Guy's Hospital, Osteoporosis Clinic, Rheumatology, London, United Kingdom, rachidainaoui@wanadoo.fr