Renal clearance of mineral metabolism biomarkers

Abstract

CKDleads to disturbances inmultiple interrelated hormones that regulate bone and mineralmetabolism. The renal handling of mineralmetabolism hormones in humans is incompletely understood. We determined the single-pass renal clearance of parathyroid hormone, fibroblast growth factor 23, Vitamin D metabolites, and phosphate frompaired blood samples collected fromthe abdominal aorta and renal vein in 17 participants undergoing simultaneous right and left heart catheterization and estimated associations of EGFR with the renal elimination of metabolites. The mean age 6SD of the study population was 71.4610.0 years and 11 participants (65%) were male.We found a relatively large mean6SD single-pass renal extraction of parathyroid hormone (44.2%610.3%) that exceeded the extraction of creatinine (22.1%67.9%). The proportionate renal extraction of parathyroid hormone correlatedwith EGFR. The renal extraction of fibroblast growth factor 23 was, on average, lower than that of parathyroid hormone with greater variability across individuals (17.1%619.5%). There were no differences in the mean concentrations of Vitamin D metabolites across the renal vein and artery. In summary, we demonstrate substantial single-pass renal extraction of parathyroid hormone at a rate that exceeds glomerular filtration. Impaired renal clearance of parathyroid hormone may contribute to secondary hyperparathyroidism in CKD.