Estradiol Rates of Change in Relation to the Final Menstrual Period in a Population-Based Cohort of Women

Abstract

Context/Objective: The aim was to characterize rates of change in serum estradiol (E2) levels across the menopausal transition and into early postmenopause. Setting/Participants: We studied the Michigan Bone Health and Metabolism Study cohort of 629 women with median age of 38 yr (interquartile range, 7) at the 1992–1993 baseline with annual assessment of E2 levels over the subsequent 15-yr period. Design/Main Outcome Measures: The purpose was to describe patterns of acceleration/deceleration in _logE2 rates of change before and after the final menstrual period (FMP) using nonparametric and piecewise regression modeling. Results: Between −10 to −2 yr to the FMP, mean fitted serum E2 population values were relatively stable. The 95% confidence bands around the slight increase in E2 rate of change 5 yr prior to the FMP included the value of no change. The fitted population mean E2 value declined 67% from 64.5 pg/ml (se = 3.6) to 21 pg/ml (se = 1.2) in the 4 yr between −2 < FMP < +2. A second significant mean E2 rate of change was identified from 6–8 yr after FMP. Fitted population mean E2 values declined 18% from 18.1 pg/ml (se = 1.3) at FMP = 6 to 14.8 pg/ml (se = 1.3) at FMP = 8. In nonobese women, the mean E2 percent decline was 42% from FMP = 6 to FMP = 8, whereas in obese women, the mean E2 percent decline over this time was 31%. Conclusions: Population mean serum E2 levels were sustained until approximately 2 yr prior to the FMP. In the ensuing 4-yr period, E2 levels declined 67%. A secondary E2 decline, commencing about 6 yr after the FMP, was observed in nonobese but not obese women.