Assessment Of Endogenous Estrogen Activity In People Having Different Exercise Habits

Life Sciences & Biotechnology Update, Feb, 2001

Evidence exists that exercising women have lower estrogen levels than sedentary women. These lower estrogen levels may be the mechanism behind their reduced breast cancer risk. Previous studies included athletes with high exercise levels, and estrogen measurements were based on a few serum samples from different times during a menstrual cycle.

This (University of Southern California) study includes identical female twins who are discordant for moderate exercise. Estradiol is measured on a daily basis from saliva samples collected during a complete menstrual cycle. Procedures and questionnaires are developed, and enrollment of eligible pairs is ongoing. Screening interviews have been conducted with 197 pairs; of these, 36 are initially eligible, but 7 declined to participate and 2 later became ineligible due to menopausal related reasons. Thus, sample collection is currently completed or underway for 27 pairs.

Estradiol and progesterone assays have been completed for 16 pairs. Although fewer eligible pairs are identified than expected, more twins will be available from additional phases of the California Twin Program. In year 3, work will continue, to screen and enroll twins, complete data entry of questionnaires, conduct hormonal assays, integrate laboratory and questionnaire data sets, and complete preliminary analyses.

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