Because it is fairly simple and inexpensive to do, "measuring leptin could be an additional marker for assessing breast cancer risk," says Richard Hajek, Ph.D., of the University of Texas's M. D. Anderson Cancer Center, lead author of the leptin study.
Produced by fat tissue, leptin tells the brain that it is time to stop eating. As body fat increases, more leptin is produced, which acts to reduce hunger and food intake; conversely, as body fat decreases, less leptin is produced, stimulating food intake.
Leptin levels change slowly over time, however, which means that they can reveal high fat intake in a person's past. This is important because high fat intake is associated with increased estrogen levels in the body and greater risk of breast cancer.
The study, published in the Proceedings for the 2003 Annual Meeting of the American Association for Cancer Research, suggests how leptin levels can change according to a pattern of eating and why leptin can tell us more about breast cancer risk than simply measuring current body fat or evaluating current fat intake.
For example, a thin woman with a low leptin level who binges on fatty hamburgers for weeks or months, with a corresponding increase in body fat, will produce a higher level of leptin. If she goes back to eating normally, her leptin level will fall but it may not return to where it was before the high fat bingeing. So while her body fat is relatively low, and her current fat intake is also low, only her leptin level may reveal evidence of the extra estrogen, and associated increased risk of developing breast cancer, produced during the binge period.
"The amount of leptin found in a woman's blood stream can indicate her accumulation of fat over the years," Hajek says. "Measuring current body weight and fat intake doesn't offer that kind of perspective."
Asked for comment, TheDoctor's Robert G. Lerner, M.D., Professor of Medicine and Professor of Pathology at New York Medical College, pointed out that this small study is consistent with mounting evidence that high fat consumption carries health risks beyond breast cancer.
"The question of the relationship of obesity to cancer risk," Lerner said, "has been examined by investigators who published their findings in a recent issue of The New England Journal of Medicine. This epidemiological study concluded that increased body weight was associated with increased death rates for all cancers combined and for cancers at multiple specific sites, not just those thought to be responsive to estrogen."
Reviewed by: John E. Morley, M.D.