Obesity, non‐protein‐bound estradiol levels, and distribution of estradiol in the sera of breast cancer patients

This study attempted to determine the relationship of nutritional status, menopausal status, presence of breast cancer, stage of disease, and tumor estrogen receptor levels to percent non‐protein‐bound estradiol (%NPBE) and percent distribution of estradiol on sex hormone‐binding globulin (SHBG) and albumin in breast cancer patients and control patients. Normal‐weight controls had significantly lower %NPBE compared with overweight controls and normal‐weight and overweight breast cancer patients. There was a significant shift in the percent distribution of estradiol from SHBG to albumin in breast cancer patients, independent of body weight. Elevated %NPBE and abnormal percent estradiol distribution on albumin persisted after mastectomy and were unrelated to menopausal status, presence and stage of disease, and tumor estrogen receptor levels. These results show that breast cancer patients have increased exposure to unbound circulating estradiol and an increased percentage of estradiol bound to albumin, which may influence the availability of estradiol, considering its low binding affinity to albumin. Because these abnormalities persist after mastectomy, the current results may be important in developing dietary intervention protocols that correct %NPBE and abnormal estradiol distribution on binding proteins.