[A study on markers of bone metabolism in patients with non hypercalciuric calcium stone--measurement of gamma-carboxyglutamic acid and hydroxyproline]

Thirty-one patients (26 male and 5 female patients) of non-hypercalciuric Ca stone formers were studied concerning their bone metabolism. We measured plasma free gamma-carboxyglutamic acid, plasma hydroxyproline, urinary free gamma-carboxyglutamic acid and urinary hydroxyproline as markers of bone metabolism. Plasma free gamma-carboxyglutamic acid level showed significantly higher in stone formers than normal controls (1.01 +/- 0.37 nmol/ml vs 0.39 +/- 0.13 nmol/ml). But no significant difference were observed in plasma hydroxyproline level (1.99 +/- 0.73 micrograms/ml vs 2.27 +/- 0.92 micrograms/ml), urinary free gamma-carboxyglutamic acid (52.0 +/- 17.6 nmol/mg.Cr vs 45.7 +/- 9.8 nmol/mg.Cr), and urinary hydroxyproline (3.87 +/- 2.02 micrograms/mg.Cr vs 3.33 +/- 1.63 micrograms/mg.Cr). In conclusion, these results suggest that abnormality of bone metabolism may be not a primary event in causing stone formation in these patients.