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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 

Fibroblast growth factor-23 is regulated by 1alpha,25-dihydroxyvitamin D.

Serum FGF-23 regulation was studied in patients with hypoparathyroidism or pseudohypoparathyroidism treated with calcitriol. Serum FGF-23 levels changed in parallel in response to changes in serum 1,25-D, suggesting that FGF-23 may be regulated by 1,25-D. In addition, the phosphaturic effect of FGF-23 may be diminished in the absence of PTH action on the kidney. INTRODUCTION: Fibroblast growth factor (FGF)-23 is a recently described hormone that has been shown to be involved in the regulation of phosphate and vitamin D metabolism. The physiologic role of FGF-23 in mineral metabolism and how serum FGF-23 levels are regulated have yet to be elucidated. Three patients with mineral metabolism defects that allowed for the investigation of the regulation of FGF-23 were studied. MATERIALS AND METHODS: Patient 1 had postsurgical hypoparathyroidism and Munchausen's syndrome and consumed a pharmacologic dose of calcitriol. Patient 2 had postsurgical hypoparathyroidism and fibrous dysplasia of bone. She was treated with increasing doses of calcitriol followed by synthetic PTH(1-34). Patient 3 had pseudohypoparathyroidism type 1B and tertiary hyperparathyroidism. She underwent parathyroidectomy, which was followed by the development of hungry bone syndrome and hypocalcemia, requiring treatment with calcitriol. Serum FGF-23 and serum and urine levels of mineral metabolites were measured in all three patients. RESULTS: Patient 1 had an acute and marked increase in serum FGF-23 (70 to 670 RU/ml; normal range, 18-108 RU/ml) within 24 h in response to high-dose calcitriol administration. Patient 2 showed stepwise increases in serum FGF-23 from 117 to 824 RU/ml in response to increasing serum levels of 1alpha,25-dihydroxyvitamin D (1,25-D). Finally, before parathyroidectomy, while hypercalcemic, euphosphatemic, with low levels of 1,25-D (10 pg/ml; normal range, 22-67 pg/ml), and with very high serum PTH (863.7 pg/ml; normal range, 6.0-40.0 pg/ml), patient 3 had high serum FGF-23 levels (217 RU/ml). After surgery, while hypocalcemic, euphosphatemic, and with high serum levels of serum 1,25-D (140 pg/ml), FGF-23 levels were higher than preoperative levels (305 RU/ml). It seemed that the phosphaturic effect of FGF-23 was diminished in the absence of PTH or a PTH effect. CONCLUSIONS: Serum FGF-23 may be regulated by serum 1,25-D, and its phosphaturic effect may be less in the absence of PTH.[1]

References

  1. Fibroblast growth factor-23 is regulated by 1alpha,25-dihydroxyvitamin D. Collins, M.T., Lindsay, J.R., Jain, A., Kelly, M.H., Cutler, C.M., Weinstein, L.S., Liu, J., Fedarko, N.S., Winer, K.K. J. Bone Miner. Res. (2005) [Pubmed]
 
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