Changes in Markers of Mineral Metabolism After Living Kidney Donation

BACKGROUND Living kidney donors (LKDs) experience reduction in kidney function, however serum phosphate (sPi) levels are lower compared to patients with chronic kidney disease matched for reduced kidney function. Mineral metabolism adaptations that occur in LKDs have not been adequately investigated. To evaluate the effect of nephrectomy on markers of mineral metabolism in LKDs compared to healthy volunteers (HV) over 12 months. METHODS Mineral parameters were evaluated in twenty-one adult LKDs and twenty HVs. Parameters included sPi, intact parathyroid hormone, fibroblast growth factor-23 (FGF23), soluble Klotho (sKl) and urinary phosphate, measured prior to donation (T0), 1 month (T1), 6 months (T6) and 12 months (T12) post-kidney donation. Statistical analyses were conducted on normalized variables and changes were assessed using 2-way analysis of variance. RESULTS Mean ages of LKDs and HVs were 54.1 ± 14.7 and 52.6 ± 8.0 years, respectively. There were no baseline clinical or biochemical differences between LKDs and HVs. In LKDs at T1, serum creatinine increased (from 75 ± 12 to 114 ± 22 μmol/L), FGF23 increased (52 ± 15 to 70 ± 19 pg/mL) and sKl decreased (564 [469-662] to 424 [375-523] pg/mL), all P less than 0.001. Changes were sustained at T12. After donation, LKDs consistently demonstrated lower sPi compared with T0, with the maximal sPi change at T6 (-0.19 mmol/L difference, P < 0.001). Other markers of mineral metabolism were unchanged in LKDs. There were no mineral differences in HVs over 12 months. CONCLUSIONS Prospective evaluation of mineral metabolism parameters in LKDs provides valuable insight into compensatory mechanisms after reduction in kidney function. Further reduction of sPi at T6 despite early alterations in FGF23 and sKl suggest adaptation of mineral metabolism continues long-term in LKDs.