The Relationships Among Estrogen Metabolites and Exercise Frequency, Duration, and Intensity in Premenopausal Women

Abstract

Estrogen is metabolized in the body through two mutually exclusive pathways yielding metabolites with different biological activities: the low estrogenic 2-hydroxyestrone and the highly estrogenic 16α-hydroxyestrone. The ratio of these metabolites (2/16) may be predictive of risk for developing breast cancer. Recent research has found that a program of aerobic exercise increased the 2/16 ratio in women at the lower end of the ratio (<1) but the specific component of exercise (frequency, duration, intensity) needed to alter the ratio is unknown. PURPOSE: The purpose of this study was to identify differences in self-reported levels of exercise frequency, intensity, and duration in women at the lower end of the 2/16 ratio (≤1) as compared with women at the higher end of the ratio (≥2). METHODS: Nineteen premenopausal women with a 2/16 ratio ≤1 and 28 premenopausal women with a 2/16 ratio ≥2 completed a questionnaire identifying their weekly average frequency, intensity, and duration of exercise during the previous year. Ordinal regression was used to determine significant differences in each variable between the two groups. RESULTS: Women with a 2/16 ratio ≥ 2 had significantly higher levels of exercise frequency (p=.038) and higher duration (p=.055) than women at the lower end of the ratio. The greatest difference between the groups was in the area of exercise frequency. Fifty percent (n=14) of the women with the higher 2/16 ratio reported an exercise frequency greater than four days per week and none of the women were inactive. In the low ratio group, only twenty-one percent (n=4) reported a frequency greater than four days per week and three women in this group were completely inactive. Sixteen women (57%) in the high ratio group reported exercise duration in the moderate (46-90 min) or high (>90 min) categories as compared with seven women (37%) in the low ratio group. Reported exercise intensity did not differ between the groups. CONCLUSIONS: Exercise frequency and duration may be the specific elements of exercise needed to alter estrogen metabolism to favor the weaker estrogen, 2-hydroxyestrone, and increase the 2/16 ratio. These results move research in the area of estrogen metabolism closer to the development of exercise prescriptions designed to increase the 2/16 ratio and possibly decrease risk for breast cancer.