There is a complex relationship between physical activity and estrogen metabolism in premenopausal women. Changes in both levels of physical activity and endogenous estrogen appear to play a role in several disease processes. It is unclear whether there is a relationship between physical activity and estrogen and its metabolites. Only 3 small cross-sectional studies have examined this relationship; 2 reported a positive relationship between physical activity and the metabolites 2-hydroxyestrone and 16α-hydroxyestrone, but the third did not. Information on the effects of physical activity on estrogen metabolites other than 2-hydroxyestone and 16α-hydroxyestrone is limited.
The aim of this cross-sectional study was to investigate in premenopausal women the association between physical activity and sedentary behavior reported for adulthood and adolescence with changes in the comprehensive profile of estrogen metabolism. Participants were 603 premenopausal women enrolled in the Nurses’ Health Study II (NHSII). Urinary levels of parent estrogens (estrone and estradiol) and 13 estrogen metabolites (jointly termed EM) were determined in luteal phase urine samples using liquid chromatography–tandem mass spectrometry. Geometric means of individual EM, metabolic pathway groups, and pathway ratios were examined for different levels of physical activity (total activity, walking or hiking, and vigorous activity), with adjustment for age, body mass index (BMI), alcohol intake, menstrual cycle length, and timing of sample collection .
High levels of physical activity in adulthood (42+ metabolic equivalent hours/week) were associated with a 15% reduction of urinary estradiol levels (Ptrend = 0.03) and a 15% lower level of 16-hydroxylation pathway EM (Ptrend = 0.03) compared with those reporting the least activity (<3 metabolic equivalent hours/week). There was no significant association for levels of 2- and 4-hydroxylation pathway EM with physical activity. There was a positive trend for high overall physical activity and the following 4 ratios: 2-pathway EM to parent estrogens (27% higher, Ptrend = 0.05), 2-pathway catechols to parent estrogens (33% higher, Ptrend = 0.03), 2-pathway catechols to methylated 2-pathway catechols (40% higher, Ptrend < 0.01), and 2-hydroxyestrone to 16α-hydroxyestrone (56% higher, Ptrend = 0.01). Walking and vigorous physical activity, like total activity, showed a positive association with estrogen metabolism, but had no association with sedentary behaviors or activity during adolescence.
These findings show an association in premenopausal women between high levels of physical activity with lower urinary levels of parent estrogens and 16-hydroxylation pathway EM and preferential metabolism to 2-pathway catechols.