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Is synthetic thyroid hormone behind your cancer

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Thyroxin and breast cancer risk

A link between diseases of the thyroid gland and breast cancer was first noted in the early 1970s, since when there have been many learned articles, which, although not conclusive, have general pointed a finger of concern.  For example Turken et al (Biomed): Women with breast cancer* have higher levels of anti-thyroid peroxidase antibodies.

(*Typically and as usual, almost all the research has been funded to look in to breast cancer, but the general conclusions of this article may well be appropriate for any cancer).

Many experts believe this link between women with thyroid disease (especially thyroid cancer) and increased risk of breast cancer does exist. Without getting too technical, early conclusions were that this was more likely due to an autoimmune response, than metastatic action or the direct action of thyroid hormones on breast cells. The following years were taken up with research that looked at the action of thyroid hormones on breast tissue, but this was deemed  inconclusive.

That is until the 2005 finding by a team of researchers at the MD Anderson Cancer Center in Texas. They were quite clear: Women with lowered thyroid activity get less breast cancer by 61 per cent. Women with high thyroid activity get more. And women with breast cancer were 57 per cent less likely to have hypothyroidism (that is where a person produces less thyroid hormone).

Disrupting the balance of your hormones

At icon we have long explained to people that your hormones are all linked in a finely balanced web. The technical name for this is homeostasis. Put one out and the rest will soon follow. Increase the levels of one, and some others will increase too, while some will decline.

The one whose level we disrupt all too often is insulin. Eating one or two big meals a day and/or eating large quantities of sugar (especially glucose) in chocolate bars or hidden in processed meals, cereals, cakes, fizzy drinks and ice cream, and/or eating white, refined carbohydrates (pasta, rice, bread, cakes) floods the blood with sugar, prompting production of insulin so that the sugar is removed from the blood stream (and stored in the cells) before it reaches the brain and puts you into a coma. Of course, the link between sugar, insulin and type-2 diabetes is now well established. In icon 1 2007 we looked at the increasing link between these factors and cancer. Poor insulin control coupled with sugary/glucose rich meals adds fuel to the fire of cancer, as research from Harvard has now proven.

But it is not merely the sugar effect. True, glucose is the favourite food of the cancer cell, but incidence of diabetes and a lack of insulin have been linked to increased risk of colon and breast cancer. As has being overweight. Indeed research from North Carolina has shown that the heavier a woman is, the less chance she has of beating the disease, once diagnosed with breast cancer. The research also concluded that losing weight during treatment i.e. controlling sugar and insulin levels reduces mortality levels. In our view we disagree with the dieticians at the hospitals like the Royal Marsden and Christie, Manchester who publish diet advice to all patients taking chemotherapy, suggesting drinking milky sugary tea, and eating cheese burgers and sticky buns.

The Thyroid

The thyroid is an organ in the front of the neck and is shaped rather like a butterfly. The thyroid glands principal hormone is Thyroxin and this has a metabolic-rate-increasing effect on almost all of the tissues of the body. Recently the University of Maryland has linked high levels of the hormone to excitable, hyperactive children and ADHD.

A lack of it (hypothyroidism) is associated with symptoms like a puffy face, tiredness, fatigue, and low energy. Other more rare symptoms include muscle cramps, hair loss, constipation, depression, memory loss and decreased libido. Since the metabolic rate declines, it is likely that the patient will also gain weight more easily.  Hypothyroidism in extremis can lead to changed (decreased) ovulation patterns in women and even loss of fertility. Equally, a number of pregnant women suffer from the disease but do not notice it, as fatigue is all too common anyway in pregnancy. One in seven women, and one in twenty men develop low thyroid hormone production as they age. Often they dont even know it.  A simple blood test can be used for diagnosis.

Why might you develop low thyroid hormone levels?

The major argument put forward is modern diet. It is a well-known fact that a lack of iodine will prevent the formation of thyroxin. However polyunsaturated oils like soya bean, corn and others that have been extracted and refined until nothing worthwhile remains, lead the field of culprits, as (according to US research) do linoleic and linolenic fatty acids; whereas coconut oil (made up of medium chain fatty acids) is supposedly helpful. Having read lots of web sites on this I find some of the arguments very flaky indeed. Im not sure anybody really knows. (In Thailand where I live, they eat large volumes of seafood iodine and fresh coconuts yet have a very high incidence of thyroid problems!)

Thyroid hormone and cancer?

Importantly, Dr Massimo Cristofanilli, leading the MD Anderson research team stated that: Thyroxin and oestrogen shared many similar pathways in the process of breast cancer. If drugs like Tamoxifen can be used to block the oestrogen pathway (via receptor sites on breast cells) then it might be possible to design drugs to block the thyroxin receptors.

Oestradiol, a particularly aggressive form of oestrogen, is known to attack receptor sites on cells and create havoc inside them particularly in the mitochondria (the power stations), such as increasing sodium levels, decreasing potassium, magnesium and oxygen levels and as a result causing the cell to power down. The result can be cancer. In women with low levels of thyroxin, there seems less cellular attack by oestradiol, and less cancer.

A hormone made in the pituitary gland directly stimulates the thyroid to produce thyroxin. (This hormone, unsurprisingly, is called thyroid stimulating hormone or TSH). Again a dietary problem may restrict production of TSH but the issue may be far more complex. Anyone who has read Pillar IV - Mental State from our series about potential cancer causes will know that the chemicals of the brain have a great effect on pituitary function. Maybe mental state is a crucial factor in this pituitary-thyroid-breast conundrum and certainly more significant than your doctors training in this area?


All seems fine with the MD Anderson theory until you realise that the test groups were all devoid of supplementation. The respondents analysed were all normal, or high, or low. Full stop.

A typical treatment for a woman with low thyroid hormone production might be supplementation using 75 mcg of synthetic thyroxin. And what prompted this article was that we received three applications for Personal Prescriptions * each from a woman with breast cancer, each with low thyroid activity, but all having been prescribed thyroxin at exactly the same dosage level (despite different ages, sizes, weights) for more than five years. They were all under 55 years old and thus outside the high-risk age band for breast cancer.

Now, there has been research on exactly this issue. A team of researchers from the Mayo clinic (Hoffman, McConahey, Brinton and Fraumeni: Jama vol 251,1984) looked into breast cancer incidence one or more years after women were given synthetic thyroxin and concluded that women taking the supplement were well below normal rates of breast cancer: (47 vs. 52.9). However, they compared the thyroxin-supplemented women with normal women and showed the rates were about 10 per cent less. Wouldnt it have been more accurate to compare the supplement users to other hypothyroid sufferers who were not using supplementation and looked for any increase? Now we have the MD Anderson study we would expect a 61 per cent lower figure when the supplemented group turned in a 10 per cent lowered figure. Was the difference due to the synthetic hormone?

Simon et al (Cancer Epidem 11 1574-8 2002) looked into much the same point and concluded that most research looks into the situation of thyroid disease, and even thyroid cancer. And this might not be relevant to simple supplementation for women with low levels of thyroid hormone. Except that, women with Thyroid cancer, after removal of the thyroid are regularly given 200 µg doses of synthetic thyroxin.  Maybe, just maybe, problems are being actually cause by the synthetic nature of the added hormone, or by providing hormone at levels that could cause problems for that particular individual. After all we do not all have exactly the same levels of hormones sloshing around in our blood streams. If thyroxin can stimulate receptors on breast cells to cause breast cancer, there clearly must be a danger in over-supplementation.

Could synthetic Thyroxin be increasing cancer risk?

Well, here we talked to two doctors, who answered our questions (but insisted on anonymity). And the fact is that the treatment for lowered thyroid activity is relatively inflexible We give them a standard dose of synthetic thyroxin.

But do they need it everyday? We assume the thyroid hormone deficiency is the same day in day out. Is that likely? No, not really.

So some days these women could have an excess of thyroid hormone? Its possible.

Did you know that excess of thyroid hormone has been linked to an increase in breast cancer risk? No. 

Regular readers know all-too-well our stance on using synthetic hormones like HRT. You add synthetic hormones to your body at your peril. Maybe synthetic thyroid hormone is equally worrying, especially if natural levels fluctuate daily. A supplemented woman (or man) could end up with a high level of thyroxin on any day. And MD Anderson scientists were absolutely clear, stating that high levels of thyroxin did cause cancer!

Low thyroid hormone levels?  1 Go and see a Naturopath quickly. 2 Take this article.

As we explained above, lack of thyroid hormone is likely to be caused by a complex inter-relationship of hormones and chemicals, and underpinning all this is often poor diet with possibly a contribution from Mental State, in turn often also affected by diet.

But it could just be down to low iodine levels. There are actually several research studies linking low iodine levels with increased rates of cancer. Few people know that the Hoxsey Therapy had potassium iodide as one of its ingredients. With low thyroid hormone problems, sadly, too many doctors reach for the prescription pad to give out synthetic thyroid hormone when they havent even checked the patients iodine levels (a 24 hour urine sample would do it.)

There is clear research in the USA that thyroxin therapy in the presence of iodine deficiency increases the risk of breast cancer and probably thyroid cancer as well. Endocrinologist, Dr. Guy Abraham (formerly of the U.C.L.A. Department of Endocrinology), is an expert who is convinced that everyone needs to be on iodine therapy until their iodine stores have been properly restored. Only after this should a doctor assess whether there is thyroid hormone deficiency. Otherwise it is obvious what might happen. A meal or two containing good levels of iodine will double up on the thyroxin therapy given.

And high thyroxin levels result in cancer. Fact. (Ghandrakant, C. et al Breast Cancer Relationship to Thyroid Supplements for hypothyroidism JAMA, 238:1124, 1976) In research amongst a group of women having screening mammograms - research that everyone seems to have ignored for 30 years - the incidence of breast cancer was twice as high in a group taking synthetic thyroxin for hypothyroidism. (12.1% in supplement group; 6.2% in controls). Worse, the incidence of breast cancer was far higher still where the women had taken synthetic thyroxin for more than 15 years (19.5%).

First take Iodine and then check again. Only if that doesnt work, consider synthetic hormone. Hintze et al agree. Their research (European Journal of Clinical Investigation, 19:527-534, 1989) clearly favours the group on iodine over the group on hormone supplement.

A qualified Nutritionist or Naturopath should be able to sort this out for you without having to resort to taking synthetic hormone supplements. If you have a breast cancer as well, we think a Naturopath should be your first port of call after leaving your diagnosis.

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