"This study indicates that exercise can lower levels of circulating estrogens and increase levels of a protein called sex hormone binding globulin (SHBG--a blood-borne protein) that binds up free-estrogen in the serum," Dr. McTiernan said. Increased levels of SHBG act to regulate the circulating levels of free, biologically available estrogens.

Dr. McTiernan noted studies showing that women on low-fat diets reduced serum levels of estradiol by 6.2 percent. The active women in the exercise study reduced estradiol level another ten percent with no dietary limitations during the study. The women who persisted with the exercise-training schedule lost an average of only 3 pounds of body fat during the 12-month study, but reduced estradiol blood levels by about one-sixth from pre-trial levels.

Although blood estrogen levels decreased, no drop in whole-body bone density was evident in the women who exercised compared with their pre-trial levels, or compared with the control group of women who merely stretched for exercise.

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Contact: Russell Vanderboom
vanderboom@aacr.org
215-440-9300
American Association for Cancer Research
15-Apr-2004