Predictors of Short-Term Changes in Serum Intact Parathyroid Hormone Levels in Hemodialysis Patients: Role of Phosphorus, Calcium, and Gender1

Abstract

Several factors have been identified as important in the pathogenesis of secondary hyperparathyroidism in end-stage renal disease, including serum calcium, phosphorus, and calcitriol. To examine the independent effects of key factors, we prospectively studied 52 new hemodialysis patients with mild secondary hyperparathyroidism (PTH, 110–670 pg/mL) treated with a standardized regimen of calcium supplements, phosphorus binders, and no vitamin D derivatives. We used simple and multivariable linear regression analysis to examine the relationship between changes in PTH (ΔPTH) levels observed over a 4-week period and various biochemical and demographic variables. By simple linear regression we found that changes in serum phosphorus (r2 = 0.31; β = 41.6; P = 0.0001), initial phosphorus concentration (r2 = 0.15; β = 33.4; P = 0.005), initial PTH level (r2 = 0.29; β = 0.58; P = 0.0001), changes in serum calcium (r2 = 0.12; β = −74.0; P = 0.01), and gender (r2 = 0.07; β = 76.1; P = 0.05) were significantly associated with ΔPTH. However, upon multivariable regression analysis, only the changes in phosphorus (partial r2 = 0.31; β = 37.0; P = 0.0001), initial PTH level (partial r2 = 0.23; β = 0.50; P = 0.0001), and gender (partial r2 = 0.05; β = 63.1; P = 0.02) remained significantly associated with ΔPTH. Neither the serum concentration of 1,25-dihydroxyvitamin D3, bicarbonate, aluminum, or albumin nor changes in the serum bicarbonate concentration, the presence of diabetes, KT/V, or age were significantly associated with theΔ PTH. Our findings are consistent with independent effects of phosphorus and gender on parathyroid gland function in patients with dialysis-dependent renal failure through mechanisms that remain to be defined.