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

Abstract

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. © 2016 American Society for Bone and Mineral Research.

Keywords: Biochemical markers of bone turnover; DXA; general population studies; menopause; osteoporosis.

Fig. 1

The three periods over which rate of bone loss was assessed around the FMP. T1 refers to 1 year before the FMP when rapid bone loss has previously been shown to begin. T2 refers to the date in early postmenopause at which U-NTX_E-POST was measured. T3 is the date at which a follow-up BMD measurement was obtained 2 to 4 years after T2. There were three time points at which U-NTX was assessed. (1) U-NTX_PRE/E-PERI refers to U-NTX measured at SWAN baseline when women are premenopausal or early perimenopausal (<3 months of amenorrhea). We assumed that U-NTX_PRE/E-PERI does not change significantly from SWAN baseline to T1. (2) U-NTX_L-PERI refers to U-NTX measured when women are late perimenopausal (≥3 months of amenorrhea, not defined by relation to FMP). (3) U-NTX_E-POST refers to U-NTX measured ≥1 and <5 years after the FMP. FMP = final menstrual period; U-NTX = urinary N-telopeptide.