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BLOG: June 2010 - December 2013
I - Breast cancer risk factors
12. Factors promoting breast cancer: hormones
As we know it, most predisposing breast cancer (BC) factors - like poor diet, prolonged stress, or chronic internal infections, all of which can negatively affect efficiency of the detox and/or immune system, become breast cancer promoting factors after its initiation by inhibiting or blocking body functions directly or indirectly related to fighting malignant growth.
Likewise, the risk factors commonly referred to as promoting breast cancer factors, are usually also predisposing factors before cancer initiation. Hence, we are talking about mainly one same group of factors, but acting under different circumstances and, sometimes, through somewhat different mechanisms.
One group of breast cancer risk factors that does not share this duality are hormones stimulating cell proliferation and their exogenous mimics (chemically similar compounds that can act like these hormones in the body). They cannot stimulate malignant growth before the malignant cells actually form, and their only effect potentially contributing to cancer formation is that they may make cancer more likely by stimulating proliferation of pre-cancerous cell forms. But this can only take place after malignant transformation has been initiated.
The group of hormones of primary concern are those stimulating cell proliferation: ovarian hormones, insulin and insulin-like growth hormone (IGF), as well as exogenous compounds that can mimic their action (environmental estrogens).
So, the most important sources of woman's hormonal exposure that can be among factors promoting breast cancer growth are:
● exposure to endogenous female sex hormones in general, and to estrogens in particular
● hormonal medical treatments
● hormonal exposure due to obesity and/or weight gain
● body size related hormonal exposure
● insulin and IGF exposure, genetic and diet-related
● exposure to environmental estrogens
Factors related to the level and balance of ovarian hormones are proven to be significant. Those are also the ones nearly exclusively publicized as the risk factors, and particularly those related to female's reproductive experience.
In addition to the internal hormone production, hormonal BC risk factors include hormonal medical treatments - particularly so called hormone replacement therapy (HRT) - as well as exposure to environmental estrogenic compounds (estrogen mimics). Of the latter, the risk factor are generally those with strong estrogenic potency; those weak or very weak generally inhibit estrogenic activity within the body.
Obesity and weight gain also affect body's hormonal activity. This effect is likely to be negative, but it cannot be assumed: there is a fairly consistent statistical evidence that overweight in premenopausal women has generally protective effect. Whether it is real, or only statistical association in nature, it is not clear at present.
Body height or, probably more appropriate, frame size is, on the other hand, directly related to the overall internal hormonal level and activity, thus its association with promoting breast cancer has the backing of this cause-effect relationship. In general, larger frame implies higher level of hormonal activity, hence also higher breast cancer risk on that basis.
Both insulin and IGF (insulin-like growth factor) stimulate cell proliferation. Exposure to these hormones can be significantly influenced by dietary patterns.
Following page addresses these breast cancer promoting factors in more detail.