Estradiol and its metabolites and their association with knee osteoarthritis

OBJECTIVE: To determine if levels of endogenous estrogen or estrogen metabolites are associated with an increased risk of developing knee osteoarthritis (OA) in women. METHODS: Serum estradiol (E2) and 2 urinary estrogen metabolites (2-hydroxyestrone and 16alpha-hydroxyestrone) with radiographically defined prevalent and incident knee OA in 842 white and African American women from the Southeast Michigan Arthritis Cohort. RESULTS: The mean age and body mass index (BMI) of women in the cohort were 42.3 years and 28.5 kg/m2, respectively. Women who developed radiographically defined knee OA had significantly greater odds of having baseline endogenous early follicular phase estradiol concentrations in the lowest tertile (0.86; OR 1.86, 95% CI 1.01-3.44 compared with women with ratios in the 0.54-0.86 range), after adjustment for other covariates. CONCLUSION: There were significant associations of lower baseline serum estradiol and urinary 2-hydroxyestrone with developing knee OA in middle-aged women.