Possible relevance of steroid availability and breast cancer

The as yet circumstantial evidence for a central role of estrogens in the promotion of human breast cancer is supported by many data. However, it has not been possible to identify breast cancer patients or women at risk by abnormally elevated estrogen levels in plasma. The concept of available, i.e., non-SHBG bound sex steroid seems to offer a better understanding than total serum steroid levels do. We demonstrated that sex steroid protein binding is decreased by free fatty acids. This finding may help to explain how the affluent Western diet and sedentary life style is related to high incidence rates of breast cancer. We have postulated that it is especially the central (abdominal) type of obesity which may increase sex steroid availability. This mechanism could be important already at the age of breast development when the sensitivity to promotion seems relatively great. It may also explain the increased incidence rates which are observed in Western industrialized countries after menopause. It seems likely that other endocrine-related cancer, such as endometrial or prostatic carcinomas are influenced in an analogous way.