Breast Cancer

There has been a huge amount of debate on the link between hormones and breast cancer, especially since the publication of the WHI study in 2002. The results of this study were widely misinterpreted, and the study itself was of such poor design that the results are of questionable significance.
The results of the WHI and The Million Women Study have been re-examined several times, and been shown to have overstated the increased risk. The most recent analysis has shown these studies have not proven an increased risk due to the lack of control for variables and poor design, conduct and follow-up of the studies. However, the majority of women who develop breast cancer have not taken any hormone replacement.
There have been numerous studies showing a small increase risk for women taking the OCP, with a more significant risk if started before age 15.

  In NSW, Australia the lifetime risk of breast cancer is 1 in 9. This compares to 1 in 7 for prostate cancer (which is now being linked to oestrogen rather than testosterone) and a 1 in 3 risk of bowel cancer at age 75.
There are 2 distinct types of breast cancer, but with the identification of gene variants (polymorphisms) there may be more than 10 types. The genetic type associated with the BRA1C gene affects women as early as in their 20's or 30's and is a very aggressive metastatic cancer which can be fatal despite early treatment. There is almost always a family history of beast cancer, and associated ovarian and prostate cancer.
  Breast cancer after menopause is most often much less agressive and likely to achieve 5 year "cure" with treatment. The family history is probably not significant.
  The least well defined group is women in the perimenopausal/early menopause stage. As breast cancers can take up to 8 years to be large enough to produce a palpable lump, some of these women will have the cancer starting in premenopause and will have the breast cancer gene.
 Probably the majority will have one or more of the gene polymorphisms being explored currently, and for whom progesterone may be most beneficial during perimenopause where oestrogen dominance is usual.
  One of the most useful things I was told at university was from a professor of surgery - that cancer is an immune surveillance disorder. If the immune system is  functioning perfectly cancer can not take hold. Cells are constantly mutating but are prevented from progressing by our immune system response. One study found about 40% of women dying from trauma had early breast cancer at autopsy, suggesting the majority of cancers are effectively dealt with before they can progress.
Unfortunately our immune systems are under seige from numerous directions, and become less effective with age (explaining the 1 in 3 bowel cancer at age 75). One major factor is prolonged exposure to stressors. Several studies have shown up to 80% of women diagnosed with breast cancer have been though unusual stress in the 2 years prior to diagnosis

It would take several hundred pages to present all the information related to breast cancer, however I believe there is enough evidence to support a reduction in risk of breast cancer using progesterone.
Several studies have shown an inverse relationship between progesterone level and risk of developing breast cancer. High levels of oestriol and progesterone in pregnancy confer a long term protective effect against breast cancer.
The peak age of breast cancer diagnosis is 60, and I wanted to understand why this was so, as postmenopausal women supposedly have no oestrogen. I have spent nearly 10 years researching , although have never seen a study specifically addressing this.
The drop in oestrogen at menopause is primarily oestradiol; oestrone continues to be produced by conversion of adrenal androgens. So there is oestrone, which binds mainly to the alpha oestrogen receptors which stimulates proliferation of breast cells, without the balancing effect of progesterone.
Obese women convert more androgen to oestrone and there is a link with BMI and breast cancer.
Recent studies have also linked higher premenopausal oestrone levels with breast cancer.
High DHEA levels (including from supplementation) have also been linked to higher breast cancer risk.
Oestriol binds mainly to the beta receptor which inhibits proliferation of breast cells. Oestradiol binds equally to both receptors.