Assessment of tubular reabsorption of phosphate as a surrogate marker for phosphate regulation in chronic kidney disease

作者：Hong Yu Ah; Lim Ji Hee; Kim Min Young; Kim Yaeni; Yang Keun Suk; Chung Byung Ha; Chung Sungjin; Choi Bum Soon; Yang Chul Woo; Kim Yong Soo; Chang Yoon Sik; Park Cheol Whee^*

来源：Clinical and Experimental Nephrology, 2015, 19(2): 208-215.

DOI：10.1007/s10157-014-0962-5

• Renal failure
• Chronic
• Phosphates
• Tubular reabsorption of phosphate
• Fibroblast growth factor 23
• Klotho

Fibroblast growth factor 23 (FGF23) and soluble alpha-Klotho are emerging potential biomarkers of phosphorus and vitamin D metabolism which change in concentration in early chronic kidney disease (CKD) in order to maintain normal phosphorus levels. Tubular reabsorption of phosphate (TRP) has been commonly used to assess renal tubular phosphate transport. The aim of this study was to evaluate the usefulness of TRP as a surrogate marker of parameters of CKD-mineral bone disease (CKD-MBD) in CKD.
A cross-sectional study was performed in 93 stable patients with predialysis CKD stage 1-5. In all patients, TRP, estimated glomerular filtration rate (eGFR), calcium, phosphate, intact parathyroid hormone (iPTH), 25-hydroxyvitamin D, serum FGF23 and urine soluble alpha-Klotho levels were measured.
As renal function declined, TRP significantly decreased (P < 0.001; r = 0.763) and both iPTH and serum FGF23 increased (P < 0.001; r = -0.598, P < 0.001; r = -0.453, respectively). The prevalence of hyperphosphatemia, secondary hyperparathyroidism, FGF23 excess and abnormal TRP increased progressively with declining eGFR. Although TRP level changed later than FGF23, abnormal levels of both TRP and FGF23 were observed earlier than changes in iPTH and serum phosphate. Decreased TRP was found to be independently associated with decreased eGFR and increased iPTH but was not associated with urine soluble alpha-Klotho or serum FGF23 level in multiple linear regression analysis.
TRP is a simple, useful and cost-saving surrogate marker of the assessment of altered mineral metabolism in CKD patients and can be used as an alternative to serum FGF23, especially for mild to moderate renal insufficiency.

• 出版日期2015-4