Bone and Mineral Metabolism and Fibroblast Growth Factor 23 Levels After Kidney Donation.

Abstract

Introduction: Prospective studies to better understand the effects of a mild reduction in kidney function on bone metabolism in otherwise healthy individuals is warranted. Materials and Methods: We measured renal function and mineral metabolites longitudinally for 1 year (days (D) 1, 2, 14, 180, & 365 post-operatively) in 74 healthy individuals who underwent kidney live donation. Changes were assessed by repeated measures ANOVA. Results: eGFR (MDRD)decreased to 59% of it's baseline on D2 (109±21 to 65±15, p<0.01) and started to increase at D3 (71±14, p<0.01), to its maximum at D180 (74±16, p<0.01), wile FGF23 increased from 60.61 (25th-75th percentile 19-81 RU/mL) at baseline to 110.99±144.56 (p<0.01) on D1 and remained higher through the study (D365: 65.87-25th-75th percentile 28-89 RU/mL). PTH rose maximally on D1 (64.9 ± 30.3RU/mL) and remained higher than baseline throughout the study (D365:52.4 ± 22.1RU/mL). Total serum Calcium levels decreased from 9,2 mg/dL to a nadir of 7.9 mg/dL on D1 (p<0.01). Serum Phosphate levels reached their nadir on D2 (2.7 mg/dL; p<0.01). At D14 total calcium and phosphate levels had returned to baseline, but phosphate levels returned down on POD4 (3.47 mg/dL;p<0.05) and D5 (3,33 mg/dL; p<0.01). Urinary fractional excretion of Pi increased from base line (11.4±5.1%) up to 16.1±10.7% until D360. Conclusions: Mild to moderate reduction in eGFR induces physiological increases in FGF23 and PTH, and decreases in serum Ca and Pi. The changes in Pi, PTH and FGF23 remains modestly yet significantly different from baseline throughout the first year after nephrectomy. The clinical consequences of elevated FGF23 following kidney donation require further studies