Serum-free gamma carboxyglutamic acid (free Gla) is a poor biochemical marker of bone resorption in early postmenopausal women

Abstract

In this study, we assessed the potential value of serum-free Gla to reflect changes of bone turnover at menopause. Serum-free Gla was measured in 49 healthy postmenopausal women and 19 healthy age-matched premenopausal women. No difference in serum-free Gla concentrations was observed between the two groups. In a double-blind longitudinal study of 36 postmenopausal women (a subgroup of the above 49 women) treated with either oral oestradiol valerate in a cyclical combination with cyproterone actate ( n = 19) or placebo ( n = 17) for nine months, the serum-free Gla concentration was unchanged with placebo and decreased by only 10% after hormonal replacement therapy. Initial serum-free Gla concentrations in postmenopausal women did not correlate with other biochemical markers of bone turnover. The predictive value of serum-free Gla concentration for the spontaneous rate of bone loss in early postmenopause was also assessed, and the marker showed no correlation to bone loss. These data indicate that the serum concentration of free Gla is not a useful marker of the bone turnover rate in the early postmenopause.