The Effect of Physical Activity on Hydroxylated Estrogen Metabolites

Abstract

1445 Estrogen is metabolized in the body through two mutually exclusive pathways yielding metabolites with different biological activities. 2-Hydroxyestrone (2-OHE1) has weak or no estrogenic activity whereas 16α-hydroxyestrone (16α-OHE1) has significant estrogenic activity. The ratio between these metabolites (2/16) may be predictive of risk for developing breast cancer. Exercise has been associated with reduced risk for breast cancer and early evidence has demonstrated that exercise may alter estrogen metabolism to favor the weak estrogen, 2-OHE1. PURPOSE: To assess the relationship between level of physical activity and urinary estrogen metabolites in premenopausal women. METHODS: Seventy-seven eumenorrheic females completed diet diaries and physical activity logs for 2 weeks prior to providing a luteal phase urine sample. Urine samples were analyzed for the concentrations of 2-OHE1 and 16α-OHE1 and the 2/16 ratio was computed. Hierarchical regression, controlling for age and BMI, was used to determine the relationships between the estrogen metabolites and MET-hrs per day of physical activity. RESULTS: Regression analysis indicated a significant positive relationship between 2-OHE1 and the 2/16 ratio with MET-hrs/day of physical activity (P < .05). CONCLUSION: These results indicate that physical activity may modulate estrogen metabolism in favor of the weak estrogen, 2-OHE1, thus producing a higher 2/16 ratio. These alterations in estrogen metabolism may represent one of the mechanisms by which increased physical activity reduces breast cancer risk. Further, these findings may encourage women to exercise more regularly to decrease their risk for developing breast cancer.