Quantifying the balance between total bone formation and total bone resorption: An index of net bone formation

Abstract

Context: Bone gain vs loss across the skeleton loss depends on the balance between total bone formation and total bone resorption. Objective: The objective of the study was to determine whether resorption and formation markers can be combined to gauge net bone formation across the skeleton. Design: The study included a cohort followed up across menopause transition (Study of Women's Health Across the Nation). Setting and Participants: Community-dwelling women, 42-52 years old, premenopausal or early perimenopausal at baseline, participated in the study. Outcome: The study included the following measures: 1) bone balance index (BBI) created by estimating the relationship between resorption (urinary N-telopeptide) and formation (osteocalcin) markers when the total formation equals the total resorption in 685 women with stable bone mineraldensity(BMD)(β5ybeforethefinalmenstrualperiod[FMP])andapplyingthisrelationship to measured bone turnover markers in 216 women beginning to lose bone (2 y from FMP); and 2) annualized percentage declines over the following 3-4 years in the lumbar spine (LS) and femoral neck (FN) BMD. Results: Adjusted for covariates, the BBI was greater (more favorable) in women with a greater body mass index (P