Serum markers of bone turnover in dialyzed patients separated according to age

Bone metabolism changes with aging in healthy population. Our aim was to determine serum markers of bone turnover in dialysis patients separated according to age.

Peritoneal dialysis (PD) or hemodialysis (HD) patients were divided into two groups. Group I (n = 30) consisted of patients older than 65 years. Patients at the age less or equal 65 years were included in group II (n = 37). In all patients we determined serum concentration of intact parathyroid hormone (iPTH), cyclase activating parathyroid hormone (CAP), osteoprotegrin (OPG) and osteoprotegrin ligand (OPGL). Cyclase inactive parathyroid hormone (CIP) was calculated. Healthy volunteers (n = 13) at the age of 42.1 years (range 23.5-70.9 years) served as controls.

When results of dialysis patients were adjusted to gender, dialysis modality and duration, group I revealed significantly lower iPTH (113.0, 10.3-606.3 pg/ml), CAP (70.0, 6.5-442.6 pg/ml) and CIP (53.3, 3.3-214.4 pg/ml) than group II (310.6, 13.7-1266.9 pg/ml for iPTH; 205.0, 9.3-887.9 pg/ml for CAP; 76.0, 2.4-399.0 pg/ml for CIP), but this group showed significantly higher serum OPG (7.39, 1.52-15.84 pg/ml) than group II (5.45, 0.95-16.47 pg/ml) and controls (2.17, 1.05-3.95 pg/ml). Only patients of group II showed significantly higher iPTH, CAP and CIP than controls (34.9, 18.9-76.9 pg/ml; 24.3, 11.2-42.6 pg/ml, 12.0, 1.0-34.2 pg/ml, respectively for iPTH, CAP and CIP).

Our results suggest that age over 65 years is a risk factor for low bone turnover in dialyzed patients. An increase in serum OPG probably reflects a paracrine mechanism of bone cells to compensate for age dependent bone loss.