[Biochemical markers of bone formation in osteoporosis]

We measured circulating bone Gla-protein(BGP) changes following short-term(2 weeks) active vitamin D treatment in elderly men with osteoporosis (73.0 +/- 9.4 years, n = 9) to evaluate osteoblastic function. We also measured serum levels of BGP(n = 245) and bone specific ALP(B-ALP) in women (n = 113) with normal lumbar bone mineral density, and evaluated the difference in clinical significance between these markers of bone formation. Serum BGP was significantly increased at the end of the first and 2nd week of daily oral 2 micrograms of 1 alpha(OH)D3 administration. BGP measurement is a clinically useful method to detect osteoblastic function after active vitamin D3 treatment. Significant positive correlations were found between age and BGP (r = 0.402, p < 0.01) or B-ALP (r = 0.494, p < 0.01). These markers were significantly higher in postmenopausal women compared with age-matched premenopausal women. The z-score of the difference in B-ALP was 1.47 and that of BGP was 0.7. Although B-ALP and P1CP in sera remained stable even at room temperature for at least 4 hours, the BGP level was significantly lower when the blood sample was kept at room temperature for more than 1 hour. These findings suggest that B-ALP is a more sensitive and stable marker than BGP in evaluating bone formation, although both markers have significant correlations with each other, and BGP is useful to detect the active vitamin D3 effect on osteoblastic function.