Tertiary 'hyperphosphatoninism' accentuates hypophosphatemia and suppresses calcitriol levels in renal transplant recipients.
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.
Evenepoel
P
P
Department of Medicine, Division of Nephrology, University Hospital Leuven, B-3000 Leuven, Belgium. Pieter.Evenepoel@uz.kuleuven.ac.be
Naesens
M
M
Claes
K
K
Kuypers
D
D
Vanrenterghem
Y
Y
D000328:Adult; D015415:Biomarkers / Q000097:blood; D002117:Calcitriol / Q000097:blood* / Q000502:physiology; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood* / Q000502:physiology; D006801:Humans; D017674:Hypophosphatemia / Q000097:blood* / Q000209:etiology / Q000503:physiopathology; D016030:Kidney Transplantation / Q000009:adverse effects*; D008875:Middle Aged; D008903:Minerals / Q000378:metabolism; D010281:Parathyroid Hormone / Q000097:blood / Q000502:physiology; D010710:Phosphates / Q000097:blood* / Q000502:physiology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D014807:Vitamin D / Q000502:physiology
D015415:Biomarkers; C000717427:FGF23 protein, human; D008903:Minerals; D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol