Serum level of under-carboxylated osteocalcin and bone mineral density in early menopausal Norwegian women.

Purpose: Serum level of under-carboxylated osteocalcin (ucOC) is considered a sensitive measure of vitamin K status, and ucOC levels are associated with bone mineral density (BMD) and fracture risk in elderly persons. The aim of this study was to assess the relationship between ucOC and BMD in early menopausal women.

Methods: The data reported here come from the enrollment in a double-blinded placebo-controlled randomized trial comprising 334 healthy Norwegian women between 50 and 60 years, 1-5 years after menopause, not using warfarin or medication known to affect bone metabolism. Total hip, femoral neck, lumbar spine, and total body BMD and serum level of ucOC and total osteocalcin were measured, and information of lifestyle was collected through questionnaires. The association between ucOC and BMD at all measurement sites was assessed by multiple regression analyses adjusting for possible confounding variables.

Results: The absolute serum level of ucOC was significantly and negatively associated with BMD at all measurements sites, both in univariate analyses (p < 0.01) and in multivariate analyses adjusting for years since menopause, smoking status and weight (p < 0.01). However, serum ucOC, expressed as percentage of the total osteocalcin level, was not associated with BMD at any site.

Conclusions: Achievement of adequate vitamin K nutritional intake is important, but ucOC expressed as percentage of total osteocalcin levels as reflection of vitamin K status does not seem to play a central role in determining BMD levels in early menopausal women.