Serum bone Gla-protein as a marker of bone growth in children and adolescents: correlation with age, height, serum insulin-like growth factor I, and serum testosterone.

Serum bone Gla-protein (BGP) was determined by RIA in 450 normal children (229 girls and 221 boys, aged 6-19 yr). Serum BGP concentrations changed in relation to age and sex with a pattern that resembles the height velocity curves for children. The increase in serum BGP occurred at the expected age of the growth spurt in both sexes, and the peak values occurred at the age of 12 yr in girls [mean, 49.2 +/- 5.6 (+/- SE) micrograms/L] and 14 yr in boys (64.0 +/- 6.3 micrograms/L). In the boys aged 10-14 yr and in the girls aged 9-12 yr, serum BGP correlated significantly with serum insulin-like growth factor I (IGF-I), serum testosterone, age and height. When the interrelationship was analyzed by means of partial correlation, with age held constant, serum BGP still correlated significantly with the other parameters, but when height was fixed there was only a correlation with serum IGF-I. In children with untreated central precocious puberty, the mean serum BGP concentration was significantly higher than in age-matched normal children [mean, 61.4 +/- 31.7 (+/- SD) vs. 29.0 +/- 10.3 micrograms/L; P less than 0.001]. Serum BGP values decreased significantly in these patients during 1 yr of treatment with a LHRH analog (buserelin) and cyproterone acetate. We conclude that serum BGP is a sensitive marker of bone growth in normal children and in children with increased growth velocity. Repeated measurements may provide useful information in the diagnosis and treatment of children with disturbances in bone turnover.