Serum bone Gla-protein in renal osteodystrophy: comparison with bone histomorphometry.

Serum bone Gla-protein (S-BGP) and other serum biochemical parameters, including alkaline phosphatase (S-AP) and immunoreactive PTH (S-iPTH), were measured in 42 patients undergoing chronic hemodialysis. Each patient also had a tetracycline-labeled transiliac bone biopsy, allowing correlations between the biochemical and trabecular bone histomorphometric parameters, S-BGP was markedly increased [64.0 +/- 74.8 (+/- SD) vs. 6.2 +/- 2.2 ng/ml in normal subjects] significantly correlated with S-AP (r = 0.53) and S-iPTH (r = 0.55) levels. S-BGP was significantly higher in the 14 patients with high turnover renal osteodystrophy (HT-ROD; S-BGP, 138.5 +/- 90.8 ng/ml) than in the 28 patients with low turnover (LT-ROD; S-BGP, 26.8 +/- 14.8 ng/ml). S-BGP was significantly correlated with the cellular parameters of bone resorption and formation (r = 0.57-0.69) and with the dynamic parameters of bone formation (r = 0.62-0.82). The extent of stainable bone aluminum was significantly negatively correlated with S-BGP (r = -0.51) and serum iPTH (r = -0.33), but not with S-AP. S-BGP measurement allowed better discrimination between LT-ROD and HT-ROD groups than did S-AP measurement. However, in the patients with LT-ROD, S-BGP did not discriminate between patients with or without osteomalacia. We conclude that S-BGP is a valuable marker for evaluating bone remodeling and, more specifically, the bone formation rate at the tissue level in hemodialyzed patients.