The aim of the study was to assess the relationship between the advancement of secondary hyperparathyroidism and the concentrations of selected calcification markers, i.e. osteopontin (OPN), osteoprotegerin (OPG), osteocalcin (OC), fetuin-A as well as fibroblast growth factor-23 (FGF-23) in peritoneal dialysis patients (PD).
Material and methods: The study included 67 patients (36 male and 31 females) aged 52.9 years (19-75 years) with chronic kidney disease (CKD) on peritoneal dialysis therapy 30.4 +/- 24.2 months. BMI was calculated using Quetelet formula. Serum Pi, Ca, albumin, fibrinogen, iPTH were performed using standard laboratory methods, while the selected bone metabolism parameters: fetuin-A, OC, OPG, OPN and FGF-23 were measured based on commercially available ELISA kits.
Results: Patients with high iPTH levels (> 300 pg/ml) had higher OC levels (median 68.5 ng/mL) comparing to patients with target iPTH, i.e. 100-300 pg/ mi (57.3 ng/mL; p = 0.003) and patients with low iPTH < 100 pg/ml (17.3 ng/mL; p < 0.0001). Also, OPN and FGF-23 concentrations were significantly higher in patients with high iPTH comparing to patients with target iPTH (1535 vs. 1001 ng/mL; p = 0.04 and 4952 vs. 702 RU/ mL; p = 0.02, respectively). Patients with increased Ca x P values (> 45 mg2/dl2) as compared with patients having lower Ca x P had higher FGF-23 (4308 vs. 678 RUlmL; p < 0.0001), higher OC (67.0 vs. 60.2 ng/mL; p = 0.049) and lower OPG concentrations (8.97 vs. 11.97 pmol/L; p = 0.02). OC strongly correlated with iPTH concentration (R = 0.78; p < 0.0001) and FGF-23 strongly correlated with Ca x P value (R = 0.74; p < 0.0001).
Conclusions: In peritoneal dialysis patients along with increment of IPTH concentrations and enchancement of calcium-phosphate imbalance, significantly rise concentrations of calcification markers such as: osteocalcin (OC), osteopontin (OPN), as well as fibroblast growth factor-23 (FGF-23).