Changes in kidney function during the menopausal transition: the Study of Women's Health Across the Nation (SWAN) - Michigan site.

Objective: The aim of the study was to examine changes in kidney function during the menopausal transition (MT) and associations with levels of sex hormones (follicle stimulating hormone [FSH], sex hormone binding globulin [SHBG], estradiol, and testosterone).

Methods: We used data from the Michigan site of Study of the Women's Health Across the Nation, a longitudinal study of the MT. For this analysis, we included women who had at least one creatinine measure before the final menstrual period (FMP) and at least one creatinine measure after the FMP (n = 101 women with 440 observations). To determine whether the declines in estimated glomerular filtration rate (eGFR) remained constant during the MT, we used local weighted regression curves to fit eGFR estimates. We examined the association between sex hormones and eGFR with longitudinal mixed models adjusting for baseline age, day of menstrual cycle, and time from FMP.

Results: At baseline, women had a mean age of 45.4 ± 2.5 years; 54% were African-American and 46% were white. Although eGFR declined significantly over time, declines were linear, consistent with declines in eGFR due to age alone rather than the MT. Total testosterone, estradiol, ratio of testosterone:estradiol, and free androgen index were not significantly associated with eGFR, whereas lower FSH (-0.039, 95% confidence interval [CI] -0.067 to -0.012) and higher SHBG (0.050, 95% CI 0.004-0.096) were associated with higher eGFR.

Conclusions: Kidney function declines during the MT. Although associated with levels of FSH and SHBG, the rate of decline in eGFR is consistent with what would be expected of age alone.