Contribution of calcium, phosphorus and 25-hydroxyvitamin D to the excessive severity of secondary hyperparathyroidism in African-Americans with CKD

Nephrology Dialysis Transplantation, 04/20/2012

Parathyroid hormone (PTH) rises with progressive chronic kidney disease (CKD) stage far more in African–American than in non–AA patients, and only a moderate component of the rise in PTH is explained by changes in serum calcium, phosphorus and 25–hydroxyvitamin in either group.

Methods

  • The authors performed a cross-sectional analysis of initial laboratory data collected on 2028 CKD patients (505 AA) from US practices using a laboratory CKD service.
  • Serum calcium (Ca), phosphorus (P), 25-hydroxyvitamin D (25-D) and plasma PTH levels were compared between the two groups.

Results

  • Mean PTH for AA exceeded PTH for non-AA in Stages 2–5 (P < 0.001, all four stages).
  • 25-D levels were higher for non-AA in Stages 1–3 (P < 0.001).
  • Serum Ca and P did not differ between groups at any stage. Full adjustment for these variables using multivariable generalized linear modeling did not remove the effect of AA race: AA PTH values exceeded non-AA values in CKD Stages 2–5 (P < 0.02, all four stages).
  • Serum Ca, P and 25-D were all inversely correlated with PTH levels irrespective of race, but all factors combined accounted for ~42% of the variance in PTH.

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