Oestrogen Dominance Can Affect Breast Cancer Treatment

The link with oestrogen and breast cancer is well established and rebalancing with bioidentical natural progesterone could be a priority, particularly for women who are overweight.


A new study, led by a team at The Institute of Cancer Research in London and The Royal Marsden NHS Foundation Trust, found that when breast cancer patients were given hormone-suppressing drugs they did reduce oestrogen levels in women. However those diagnosed as obese and with breast cancer still had oestrogen levels remaining after treatment that were still more than double those of women of normal weight.

There is a normal weight gain at menopause, though this can be increased by high oestrogen levels as when progesterone levels are low its natural action to act as a diuretic and regulate thyroid production – both of which are factors in weight gain – is restricted. Over three-quarters of breast cancers require oestrogen to grow, so one of the main ways of treating the disease is by blocking the hormone’s production or action and the most natural way to do this is to ensure that progesterone and oestrogen levels are in balance and that oestrogen dominance is dealt with.

Obese women will have higher levels of oestrogen than women of normal weight and of the many reasons to maintain a healthy weight it would seem that ensuring good progesterone levels to protect against breast cancer initially or to deal with drug treatment is essential.

Senior author Professor Mitch Dowsett, a team leader in the Breakthrough Breast Cancer Research Centre at The Institute of Cancer Research and head of the academic department of biochemistry at The Royal Marsden, said: “Our findings are based on laboratory studies, so we would need to carry out clinical trials to tell us whether women with a higher BMI would benefit from changes to their treatment. Women with higher BMIs should certainly not be alarmed by this finding or stop taking their treatment. Our study takes us a step closer to understanding which of the treatment options available might be the most suitable for individual women.”


Interestingly their options do not seem to include advocating natural progesterone supplementation but confirm a recent study that indicated the aromatase inhibitor anastrozole was no more effective than older-style tamoxifen in women with higher BMI.

If you are wondering if you are of normal weight, then in the UK, the healthy weight range BME (Body Mass Index) is considered 18.5 to 25, between 25 and 30 is overweight and above 30 is obese.