Recently, the scientific world has been finding that the relationship between estrogen and obesity are much closer than they previously thought. In postmenopausal women especially, individuals with higher levels of body fat were found to be at an increased risk for developing breast cancer than their skinnier counterparts. Researchers noticed an 11% increase in the prevalence of obesity in postmenopausal women between 1988 and 2000. The serum estrogen concentrations in a woman with a body mass index (BMI) of 30 or higher is 60%-219% higher than a women with lower BMI, and the breast cancer risk increases by 18% for every 5-point change in BMI (“DDT and breast cancer in young women”) .The implications of these findings suggest that there are ways to prevent certain types of breast cancer in women, simply by monitoring weight and instituting a diet and healthy living plan when necessary. It is important for women to know which factors can be controlled in order to increase their ability to prevent this disease. A decrease in body fat will subsequently decrease the amount of estrogen in the blood and therefore decrease the risk for developing certain types of breast cancers.

In a a more recent set of experiments, scientists have shown that the onset of menopause contributes to obesity in many women. This occurs because of estrogen receptors in the hypothalamus, which become deactivated at menopause, cause the individual to increase intake of food and other factors leading to weight gain. A specific receptor called estrogen receptor alpha has been shown to regulate both food intake and energy expenditure (American Chemical Society, 2007). One of the areas currently being studied in the brain is called the ventromedial nucleus (VMN), an area of the hypothalamus that is rich with these specific receptors. In test animals that had a decrease in estrogen in the hypothalamus, there was a subsequent decrease in overall metabolic rate and an increase in visceral fat, despite a constant caloric intake.

It has become apparent that in women, there is a vicious cycle occurring with their physical health that no individual is exempt from. More research is showing that menopause triggers certain events in the brain which cause an increase in body fat, as a result of decreased estrogen in the body. In response to this problem (and other symptoms characterized by menopause), women will seek out hormone replacement therapy in order to try and reverse the post-menopausal symptoms. However, the increase in body fat is already causing damage to their system by releasing even more estrogen into their bloodstream. The increase in serum estrogen levels puts the individual at increased risk for developing breast cancer, and the rise in obesity is being linked to heart disease and diabetes.

Listen to a news report discussing the link between the climbing obesity rates and rising cancer rates

The biosynthesis of estrogens differs between premenopausaland postmenopausal women. Premenopausal women mainly synthesizeestrogens in the ovary. However, in postmenopausal women ovarianbiosynthesis is replaced by peripheral site synthesis, and inobese postmenopausal women, adipose tissue is the main sourceof estrogen biosynthesis. (“Obesity and Estrogen”).   There have been studies conducted that showed that women who had developed post-menopausal breast cancer, had a rising level of estrogen as well.

From review of the menstrual cycle, menopause occurs once the follicle stock has been exhausted from a woman’s ovary, which means the estrogen production does not come from the follicles (which produces high levels of estrogen in order to develop the mature graafarian follicle).  So, this estrogen must be coming from peripheral sites (other organs, adrenal glands) that can cause an increase in estrogen, but obese women who are producing it from fat storages throughout the body are expected to have higher levels of estrogen, and have been linked to higher incidences of breast cancer.

Estrogen receptors have been shown to be linked with the tumors in breast cancers.  A specific estrogen receptor- alpha, has been shown to increase proliferation of cells.  The upgrade of this specific estrogen receptor in the myoepithelium of the lobules and ducts of mammary glands has been shown in obese women whom had developed tumors in the breast. This connection between circulating estrogen levels, obesity, and breast cancer has been linked to many cases studies.  Other receptor studies in tumor development have been PR (progesterone) and HER-2 (human epidermal growth factor-2), and there is research showing a positive correlation with BMI.  (“Obesity and Estrogen”).

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