PTH and the Risks for Hip, Vertebral, and Pelvic Fractures Among Patients on Dialysis

Abstract

Few investigations have described fracture risk and its relation to disorders in calcium (Ca), phosphorus (P), and parathyroid hormone (PTH) metabolism in the end-stage renal disease population. Laboratory values for Ca, P, and PTH were obtained from Dialysis Morbidity and Mortality Study (DMMS) Waves 1 to 4. Additional data available from the US Renal Data System were used to determine the incidence and associated costs of hip, vertebral, and pelvic fractures in 9,007 patients with nonmissing laboratory values and Medicare as primary payor. Cox proportional hazards and Poisson models were used to analyze time to first fracture and numbers of fractures, respectively. There was no association between Ca or P values and risk for fracture; risks for vertebral and hip fractures and PTH concentrations were U shaped and weakly significant using Poisson regression (P = 0.03). The age- and sex-adjusted mortality rate after fracture was 2.7 times greater (580/1,000 person-years) than for general dialysis patients from the DMMS (217/1,000 person-years). Mean total episodic costs of hip, vertebral, and pelvic fractures were 20,810 dollars +/- 16,743 dollars (SD), 17,063 dollars +/- 26,201 dollars, and 14,475 dollars +/- 19,209 dollars, respectively. Using data from the DMMS, there were no associations between Ca and P concentrations and risk for fracture. Risks for hip and vertebral fracture were associated weakly with PTH concentration, with the lowest risk observed around a PTH concentration of 300 pg/mL (ng/L). Fractures were associated with high subsequent mortality and costs. Prospective studies are needed to determine whether therapies that maintain PTH concentrations within or near the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative range will result in fewer complications of disordered mineral metabolism.