Bone Mineral Density: Serum Markers of Bone Turnover and Their Relationships in Peritoneal Dialysis

Background: The usefulness of bone mass measurements and bone turnover markers to estimate the risk of fracture and the type of underlying renal osteodystrophy are not well established in patients on peritoneal dialysis (PD).

Objective: To assess bone mass using total and regional bone densitometry in a group of patients on PD and to determine if serum markers of bone turnover identify patients with low bone mass.

Methods: Bone densitometry was studied by dual-energy x-ray absorptiometry (DEXA), and bone turnover using several serum markers, in 65 patients on PD. Bone mass was classified as normal, osteopenic, or osteoporotic according to World Health Organization criteria based on bone mineral density (BMD) T scores.

Results: T scores in the osteopenia range were present at the lumbar spine (LS) in 44.6% (45% of men and 44.4% of women) of patients and at the femoral neck (FN) in 56.9% (55% of men and 58% of women). T scores in the osteoporosis range were present at the LS in 13.8% of patients (10% of men and 15.5% of women) and at the FN in 21.5% (30% of men and 17.7% of women). Patients with BMD T scores in the osteoporosis range at both regions had increased serum intact parathyroid hormone (iPTH) levels compared to patients in the osteopenic/normal range. Bone mineral content in the whole skeleton (TBMC) correlated negatively with iPTH (r = -0.34) and with total time on dialysis (r = -0.26); in multivariate analysis, only iPTH correlated negatively with TBMC (B = -0.26, p = 0.03). No correlations were found between the other bone markers and BMD T scores at the FN or LS. There were no significant differences in absolute BMD or BMD T scores at the LS or FN between patients with and patients without fractures.

Conclusions: BMD T scores in the osteopenia/osteoporosis range were observed at the LS in 58.4% of these patients on PD and at the FN in 78.4%. TBMC correlated negatively with iPTH. There were no correlations between markers of bone turnover and bone mass measurements at the two skeletal regions, although patients with BMD T scores in the osteoporosis range had increased serum iPTH levels. Bone mass measurements were not different between patients with and patients without fractures.