Thyroid hormone increases breast cancer - Thyroid UK

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Thyroid hormone increases breast cancer

Margo profile image

I was quite shocked to read this yesterday:

Are there any reliable iodine tests that I can take in the UK

34 Replies

Thanks for sharing that.

I am tested really deficient, but doctors wont recommend taking any iodine.. I do know that iodine is needed in breast tissue and being deficient increase the risk of breast cancer, but I guess I now should take it more seriously and start taking iodine regardless what doctors say.

Margo profile image
Margo in reply to Justiina

Justiina, I don't have a high opinion of doctors/consultants/experts personally. Did you get an NHS test? Did you have to ask for it?

Justiina profile image
Justiina in reply to Margo

I live in Finland and got my iodine test through complete thyroid panel as it was a part of it. It also measured selenium, bromine and arsenic .

Here is the link to the test I took as it states Thyroglobulin should measured at the same time, it explains why it is good to have it with urine test, as just urine test might not be accurate

I had low iodine and high thyroglobulin.

Margo profile image
Margo in reply to Justiina

Thank you Justiina

Anyone else confused about the iodine debate?

Someone posted recently on the form of iodine called"Nascent Iodine"Looks really interesting,but I keep reading that if hypo & on replacement therapy,you should not go near it,or seaweed etc


I agree Naomi8 it is hard to make sense of what to do.

The breasts and thyroid need different forms of iodine. I've read a lot about the controversy as well although Dr. Brownstein discounts it as others do.

Grey Goose posted an interesting video. While another myth going around is whether liquid iodine will absorb externally. Start at minute 23 because of what he says about D3 and the latter portion is about the iodine I think.

Margo profile image
Margo in reply to Heloise

Thanks Heloise will do.

Hi Margo,

thanks for posting,

I had breast cancer 21 years ago and diagnosed hypo. just over 4 years ago.

I wonder does this mean I have always had a iodine deficiency or because I am now on thyroxine I am more prone to iodine deficiency.

I am going to now get a iodine test.

Interesting to see what your result is browny.

I've looked into iodine testing and I'm not convinced they are reliable. The iodine loading test (Urine) is supposed to be the best but even this can give false results apparently. Plus, I can't find anyone in UK to do this one - only one I found had to be sent to the States.

I use patch test on same part of arm each time and the length of time for patch to disappear has been increasing over time. (I have been supplementing with iodine).

Iodine is a complete mystery to me - experts seem to be either vehemently for or vehemently against it, lol

Margo, this link discusses urine tests and iodine loading/urine tests to find iodine status but I don't know whether the loading test is available in the UK

Mark Vanderpump says milk is an important source of iodine in the UK and of his study finding iodine deficiency in teenage girls ‘One cup of milk contains about half the amount of iodine needed per day. A possible explanation for our findings may be that teenage girls are drinking less milk and are less likely to have milk and cereal for breakfast. The solution could be to add iodine to the salt used in products such as bread as has been done in for example Denmark.’

The reason for that is that commercial (not organic) milk producers wipe the udders with iodine (not because there is lots of iodine in milk) - if they still do - no doubt it's now an antibiotic or pharmaceutical antibacterial agent or soon will be.

Margo profile image
Margo in reply to Clutter

Thanks Clutter.

I do worry about this. I am vegan, so I suspect I am iodine deficient, but I am so scared of supplementing and causing an antibody flare up. Does anyone know which sort of iodine is needed by the breasts? I didn't know there were different kinds.

Just read your link Margo, and now I am even more worried. How do you even test for iodine deficiency?

Margo, I did a urine iodine test through Genova, very easy to do. My result was 20!! should be 150-199 so I started to take Lugols' iodine after following the protocol to remove halides. It's all in the book.

Because I have Hashi's I was concerned, but managed to reduce TPO by going gluten and lactofree. The debate rages on about whether or not to take Iodine. Having read several books about it I decided to take it. I also take Selenium tablets.

It can't be a coincidence that as more people have thyroid problems, Iodine intake is very reduced compared to 50 years ago and there are many more cases of breast cancer!!

All you can do is read the available research and make up your own mind. best wishes.

Margo profile image
Margo in reply to crimple

Thanks Crimple.

The uk was declared to be iodine deficient in 2011, ( And I asked on the 2012 forum (. whether, in light of this finding, our tsh threshold would be brought down to be the same as Germany. The reason given for the uk tsh threshold being higher was originally because German soils were iodine deficient. Of course there was no reply and bugger all has been done in the form of introducing iodine in salt, or reducing the tsh threshold.

I have hashimotos controlled by medication. ( NDT).... I bought some lugols iodine and took it for a year or so..... I didnT notice any effects at all, and eventually stopped taking it. (As you do).....

Xx g

I wonder what Dr Malcolm Kendrick would have to say about Dr Brownstein's interpretation of the research statistics?

In his book 'Doctoring Data' he gives many examples of how statistics are misused for marketing purposes, and explains how we all need to become alert to this.

bobsmydog profile image
bobsmydog in reply to WildDeer

I wondered that so had a look at his blog and this question was asked, but I'm still trying to get my head around the figures

Marc says:

Dr Brownstein,

Are you sure you linked the correct article ?

This is what the Abstract of JAMA. 9.6.1976. Vol. 236, N. 10. 1124 ( says :


This study was undertaken to determine the relationship between thyroid supplements and breast cancer. The incidence of breast cancer among the patients who received thyroid supplements was 12.13%, while in the control group it was 6.2%. The incidence rate of breast cancer was 10%, 9.42%, and 19.48% among patients who received thyroid supplements for one to five, 5 to 15, and for more than 15 years, respectively. The incidence of breast cancer among nulliparous women who received thyroid supplements was 33%, while in the nulliparous women without thyroid supplements the incidence was only 9.25%. Even in a specific age group, the incidence rate of breast cancer was higher among patients receiving thyroid supplements, when compared to the control patients in the same age group.

Where do you get the 200% number from ?


Best Regards,


David Brownstein says:


For women who took thyroid hormone for more than 15 years, the

incidence of cancer was 33%, for those without thyroid hormone, it was 9.25%. 33/9.25 is 3.56 or 256% increased (I rounded the number down).


I have just been diagnosed with breast cancer 3 days ago I have also had metastatic thyroid cancer. I strongly believe there is link, if anybody has any links to research I would be very grateful indeed as my surgery and treatment is being planned. Many Thanks

lucylocks profile image
lucylocks in reply to sorrel89

Hi Sorrel89,

Sorry to hear of your diagnoses.

I do not have any links to research, I just wanted to say good luck with the surgery and treatment.

I had breast cancer 21 years ago, age 39. I had surgery and treatment so understand what you are going through.

Just thought I would let you know to give you some encouragement.

Good luck and best wishes browny

Does it really mean that taking replacement hormones causes cancer or that hypo (and perhaps hyper on block and replace) people being treated have rubbish immune systems and are therefore more likely to get cancer? Dr B (the iodine guru) cannot KNOW that all those women were iodine deficient. Probably some were and some weren't.

Correlation is not causation.

Oh, I do so agree with you! It also means that hormones are unbalanced and you're likely to be estrogen-dominant, which causes breast cancer. This is just scare-mongering to sell his book.

Something along these lines was posted a while ago. So then I found this :

Which suggests the opposite.

Also, given the fact that when you are taking thyroid hormone replacement, you are also taking iodine (four atoms of iodine for every molecule of T4, which are removed and recycled) taking extra iodine suppléments could very well mean an excess of iodine. Excess iodine can cause all sorts of problems, including triggering Hashi's if you haven't already got it.

That is reassuring, thanks for posting it. It does appear to relate to hyperthyroid patients who then subsequently went hypothyroid, rather than people who began hypothyroid. It states "There was also no breast cancer excess among women who remained euthyroid (SIR = 1.0)". Does anyone know what S I R means?

It was basically about women taking thyroid hormone replacement, whether they'd been hypo or hyper.

Sorry, I Don't know what SIR means.

It's really nice to see that study, thanks again for posting it.

You're welcome. I didn't want people worrying about it.

Even googling has not revealed what SIR means. The only medically relevant definition is "Standardized Incidence Ratio" but that doesn't seem to fit the context. A mystery!

Oh, I think it does - although I couldn't explain it! Never have understood ratios. lol

Just reread the study and it makes sense now, it is just saying in eurathyroid patients the standardised incidence ratio was 1, that is the same as normal.

I have read this before and the truth is that being hypothyroid causes all kinds of Cancers, so thus, people taking [mostly all take Levo/t4] thyroid hormone, get Cancer. T4 leaves most people hypo to some degree and there are many good doctors out there, that know it is poor treatment. T3 is the active hormone anyway. Some people don't convert well. Also, Cancer i believe, is Autoimmune, so is the leading cause of Hypothyroidism..Hashimoto's. Once you get one autoimmune condition, you can get others..again, a link, if you call it one.

Thanks faith63 your post makes good sense.

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