Serum bone GLA protein (BGP) was measured by radioimmunoassay in 42 patients (age,
47.5 +/- 16.6 years; serum creatinine, 4.32 +/- 1.9 mg/dl) with predialysis chronic
renal failure (CRF). Nineteen patients were studied within a short period of time,
while 23 were followed with repeated measurements of serum BGP, creatinine, iPTH,
and alkaline phosphatase (AP) for a mean period of 17.1 +/- 8.1 months. Eleven of
these patients were treated with 1,25(OH)2D3 for a mean of 16.8 +/- 6.4 months. In
23 patients at various stages of CRF, a transiliac bone biopsy was performed for histomorphometric
evaluation. In the untreated patients, serum BGP was higher than normal and showed
a positive correlation with creatinine levels (P less than 0.001). Serum BGP was also
positively correlated with iPTH, AP, serum phosphate, active resorption surface, active
osteoblastic surface, osteoid surface, and volume. During treatment with 1,25(OH)2D3,
BGP, iPTH, and AP were significantly lower than in the untreated patients. The reduction
in iPTH and BGP was proportional, while BGP and AP no longer correlated. Repeated
measurements of BGP during the long-term follow-up showed a progressive rise in the
untreated patients and a downward course of BGP levels during treatment. In conclusion,
serum BGP increases progressively in CRF, rising with advancing renal damage in close
correlation with iPTH, AP, and the severity of renal osteodystrophy. Treatment with
1,25(OH)2D3 causes a parallel decline in BGP and iPTH levels and dissociation between
BGP and AP can be observed. Compared to AP, BGP seems to be a more reliable index
of secondary hyperparathyroidism and potentially more useful in the long-term monitoring
of treatment with 1,25(OH)2D3.