CKD progresses more rapidly to
ESRD among African Americans compared with Caucasians. Disordered
mineral metabolism is more severe among African Americans with CKD, which might partially explain the accelerated progression of their
kidney disease. Here, using data from the African American Study of
Kidney Disease and
Hypertension, we evaluated longitudinal changes in serum levels of
fibroblast growth factor-23 (FGF23),
parathyroid hormone (PTH),
phosphate, and
25-hydroxyvitamin D in a subset of 420 participants followed for a median of 4 years. We also examined the association of baseline levels of
mineral metabolites with risk for
ESRD or death in 809 participants. FGF23, PTH, and
phosphate levels rose over time; participants with faster rates of decline in measured GFR had the greatest increases in these parameters (P<0.01 for each). Higher baseline levels of FGF23, PTH, and
phosphate each associated with increased risk for
ESRD or death independent of GFR. FGF23 exhibited a dose-response relationship with outcomes (HR=1.30 per doubling, 95% CI=1.15-1.47; HR=2.24 for highest compared with lowest quartile, 95% CI=1.39-3.60), whereas PTH and
phosphate showed nonlinear relationships.
Vitamin D insufficiency (<30 ng/ml) was present in 95% of participants, but lower levels did not independently associate with outcomes. Using death-censored
ESRD as the outcome produced qualitatively similar results. In conclusion, abnormalities of
mineral metabolism worsen with progressive CKD and associate with higher risk for
ESRD among African Americans with hypertensive
nephrosclerosis.