Tertiary 'hyperphosphatoninism' accentuates hypophosphatemia and suppresses calcitriol levels in renal transplant recipients.

Abstract

Hypophosphatemia and inappropriately low calcitriol levels are frequently observed following successful renal transplantation. Fibroblast growth factor-23 (FGF-23) is a recently characterized phosphaturic hormone that inhibits renal 1 alpha-hydroxylase activity and may be involved in the pathogenesis of both phenomena. The following hypotheses were tested: pretransplant FGF-23 predicts posttransplant FGF-23, FGF-23 predicts posttransplant hypophosphatemia and FGF-23 is associated with decreased calcitriol levels independent of renal and parathyroid function. Serum biointact parathyroid hormone (PTH), calcidiol, calcitriol, full-length FGF-23, calcium and phosphate were monitored in 41 renal transplant recipients at the time of transplantation (pre) and 3 months thereafter (post). In addition, serum phosphate nadir in each individual patient was identified and urinary fractional excretion of phosphate (FE(PO4)) at month 3 was calculated. High FGF-23(post) levels were independently associated with high FGF-23(pre), low calcitriol(post) and high calcium(post) levels. FGF-23, but none of the other mineral metabolism indices, was an independent predictor of the phosphate nadir in the early posttransplant period. A high FGF-23(post) level was independently associated with a high FE(PO4). High FGF-23(post) and creatinine levels and low PTH(post) levels were independently associated with low calcitriol(post) levels. In conclusion, our data indicate that persistence of FGF-23 contributes to hypophosphatemia and suboptimal calcitriol levels in renal transplant recipients.

• Authors: P Evenepoel, M Naesens, K Claes, D Kuypers, Y Vanrenterghem
• Journal: American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons (Am J Transplant) Vol. 7 Issue 5 Pg. 1193-200 (May 2007) ISSN: 1600-6135 [Print] United States
• PMID: 17359508 (Publication Type: Clinical Trial, Journal Article)

Chemical References

• Biomarkers
• FGF23 protein, human
• Minerals
• Parathyroid Hormone
• Phosphates
• Vitamin D
• Fibroblast Growth Factors
• Fibroblast Growth Factor-23
• Calcitriol

Topics

• Adult
• Biomarkers (blood)
• Calcitriol (blood, physiology)
• Fibroblast Growth Factor-23
• Fibroblast Growth Factors (blood, physiology)
• Humans
• Hypophosphatemia (blood, etiology, physiopathology)
• Kidney Transplantation (adverse effects)
• Middle Aged
• Minerals (metabolism)
• Parathyroid Hormone (blood, physiology)
• Phosphates (blood, physiology)
• Predictive Value of Tests
• Prospective Studies
• Vitamin D (physiology)