Body size in relation to urinary estrogens and estrogen metabolites (EM) among premenopausal women during the luteal phase.

Estrogen metabolism profiles may play an important role in the relationship between body size and breast carcinogenesis. Previously, we observed inverse associations between current body mass index (BMI) and plasma levels of parent estrogens (estrone and estradiol) among premenopausal women during both follicular and luteal phases. Using data from the Nurses' Health Study II, we assessed whether height, current BMI, and BMI at age 18 were associated with the urinary concentrations of 15 estrogens and estrogen metabolites (jointly referred to as EM) measured during the luteal phase among 603 premenopausal women. We observed inverse associations with total EM for height (P (trend) = 0.01) and current BMI (P (trend) = 0.01), but not BMI at age 18 (P (trend) = 0.26). Six EMs were 18-27% lower in women with a height 68+ versus ≤62 in., primarily in the methylated catechol pathway (P (trend) = 0.04). Eight EMs were 18-50% lower in women with a BMI of 30+ versus <20, primarily in the 2-catechol and methylated catechol pathways (P (trend) < 0.001 for both). Our results suggest that height and current BMI are associated with estrogen metabolism profiles in premenopausal women. Further studies with timed urine and blood collections are required to confirm and extend our findings.