Predictors of short-term changes in serum intact parathyroid hormone levels in hemodialysis patients: role of phosphorus, calcium, and gender.

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 (deltaPTH) 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; beta = 41.6; P = 0.0001), initial phosphorus concentration (r2 = 0.15; beta = 33.4; P = 0.005), initial PTH level (r2 = 0.29; beta = 0.58; P = 0.0001), changes in serum calcium (r2 = 0.12; beta = -74.0; P = 0.01), and gender (r2 = 0.07; beta = 76.1; P = 0.05) were significantly associated with deltaPTH. However, upon multivariable regression analysis, only the changes in phosphorus (partial r2 = 0.31; beta = 37.0; P = 0.0001), initial PTH level (partial r2 = 0.23; beta = 0.50; P = 0.0001), and gender (partial r2 = 0.05; beta = 63.1; P = 0.02) remained significantly associated with deltaPTH. 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 the deltaPTH. 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.