In order to investigate the pathophysiology of anticonvulsant induced osteopenia, circulating levels of bone γ-carboxyglutamic acid containing protein (BGP) and urinary excretion of BGP were measured in sixteen childlen on chronic anticonvulsant therapy and twelve control children. Using microdensitometry analysis, osteopenia was found in 25% of the anticonvulsant therapy group, but was not observed in the control group. Serum levels of BGP and Al-P were significantly increased in the anticonvulsant group compared to those in control group (P<0.05, P<0.01), respectively.
Urinary excretion of BGP and Hydroxyproline showed a increasing tendency in the anticonvulsant group, but it was not statistically significant. There was no significant difference in serum levels of Vit D metabolites, PTH, calcitonin, Ca, P or urinary excretion of Ca, P between the two groups. It is suggested, therefore, that increasing BGP levels in children receiving anticonvulsant therapy is responsible in part for the occurrence of anticonvulsant induced osteopenia.