Urinary N-telopeptide and Rate of Bone Loss Over the Menopause Transition and Early Postmenopause.

The purpose of this study was to assess the ability of urinary N-telopeptide (U-NTX) to gauge rate of bone loss across and after the menopause transition (MT). U-NTX measurement was measured in early postmenopause in 604 participants from the Study of Women's Health Across the Nation (SWAN). We examined the association between U-NTX and annualized rates of decline in lumbar spine and femoral neck bone mineral density (BMD) across the MT (1 year before the final menstrual period [FMP] to time of U-NTX measurement), after the MT (from time of U-NTX measurement to 2 to 4 years later), and over the combined period (from 1 year before FMP to 2 to 4 years after U-NTX measurement). Adjusted for covariates in multivariable linear regression, every standard deviation (SD) increase in U-NTX was associated with 0.6% and 0.4% per year faster declines in lumbar spine and femoral neck BMD across the MT; and 0.3% (lumbar spine) and 0.2% (femoral neck) per year faster declines over the combined period (across and after the MT) (all p < 0.01). Each SD increase in U-NTX was also associated with 44% and 50% greater risk of fast bone loss in the lumbar spine (defined as BMD decline in the fastest 16% of the distribution) across the MT (p < 0.001, c-statistic = 0.80) and over the combined period (across and after the MT) (p = 0.001, c-statistic = 0.80), respectively. U-NTX measured in early postmenopause is most strongly associated with rates of bone loss across the MT, and may aid early identification of women who have experienced fast bone loss during this critical period.