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Saturday March 23rd 2019


Thyroid/Breast Cancer Connection!

Post Published: 22 July 2010
Category: Guest Bloggers, Thyroid And Breast Cancer Connection
This post currently has 11 responses. Leave a comment

I’m a fan of aggressive prevention, and what better diagnosis to prevent than cancer? Many of my patients don’t realize that the hormonal balancing and nutraceutical prescriptions we co-create in my integrative medical practice are often in the service of cancer risk reduction. More specifically, many of my patients don’t realize the crucial link between healthy boobs and their thyroid. Who knew?

I do not mean to be glib about the diagnosis of breast cancer. I personally have a positive family history and know first-hand the deeply emotional and complicated issues reflected in this diagnosis. But what troubles me is the tremendous distortion I’ve seen in the media’s oversimplification of how hormones “cause” breast cancer. The truth is far more nuanced and worth digesting.

It is not surprising to find a link between thyroid troubles and breast cancer. Look at the epidemiology – both conditions share a predominance in women, with a peak incidence in menopause.  What else do the breast and thyroid have in common? Both tissues take up and use dietary iodine.  Research has shown that iodine or iodine-rich seaweed inhibits breast tumor growth, and is further supported by the outrageously low rates of breast cancer in Japanese women living in Japan and eating a traditional Japanese diet (for more data on this, see Daphne Miller’s new book, The Jungle Effect). When Japanese women move to the U.S. and consume a standard American diet (SAD), their breast cancer rates approach the epidemic levels that we have here in the States.

Let’s address specifically the role of thyroid optimization and risk of cancer generally, and, specifically, breast cancer.  Here’s what we know:

  • Women with breast cancer are 2 times more likely to have thyroid antibodies than women without breast cancer
  • Pre-menopausal women with thyroid cancer are at increased risk for breast cancer 5-20 years later according to MD Anderson Cancer Center. Breast cancer is not associated with an increased risk of thyroid cancer, which suggests that thyroid cancer treatment with post-surgical radio-active iodine (RAI) was the reason for the greater risk.
  • Non-toxic goiter (an enlarged thyroid) is twice as common in women with breast cancer
  • Survival from breast cancer is improved if your TSH is normal (i.e., your are “euthyroid”). In women with breast cancer with underactive thyroids, survival from breast cancer was 0% at 16 months, and in euthyroid survivors, survival at 16 months was 100% (older data – Journal of the American Medical Association, 1963)
  • Thyroid problems that are benign (non-malignant, such as Graves, Hashimoto’s thyroiditis) correlate with risk of cancer (bladder, kidney, blood, and thyroid cancer), particularly in women with low free T3 and normal TSH (Thyroid, 1998).

Unfortunately, there is no clear consensus about how thyroid hormone may influence breast tissue. In fact, there are additional studies showing conflicting results, such as a 2005 study, also from M.D. Anderson, showing reduced risk of breast cancer in hypothyroid patients.

Most research to date has focused on the role of sex hormones (estrogen, progesterone, testosterone) on breast tissue, but thyroid hormone shares similar mechanisms in control of cell growth and proliferation.

What about iodine? Before you start munching on kelp, a few words.  Many of us here in the US are iodine deficient, and this was addressed here in the States and in other industrialized countries by adding iodine to salt several decades ago. Yet 45% of households don’t use iodized salt. Now we are starting to see areas of iodine deficiency again. However, both slightly too much and slightly too little iodine can be a problem for you. Excess iodine in some of us thyroid-sensitive folk can worsen autoimmune thyroiditis. Overall, in the US we consume an average of 240 micrograms of iodine per day, and 15% of women in the US are moderately to severely iodine deficient. In Japan, the average consumption is 12 mg of iodine, a 50-fold greater amount. Why don’t the Japanese have a problem with consuming too much iodine? Does it protect them from breast cancer? Do they have a higher rate of thyroid problems? No – their rates of thyroid dysfunction are similar to ours.

What to do? Regarding iodine, best bet is to test your iodine and see how much you need individually. Many of us take a multivitamin with 100-200mcg of iodine, and that is probably a safe amount, but may be excessive if you also consume a lot of shellfish and/or sea vegetables. I favor testing – moderate to severe deficiency is defined as urine excretion of iodine of less than 50 mcg/L.

Regarding breast cancer risk and thyroid dysfunction, I believe the safest route given the findings is the voice of reason: seek euthyroidism (in my book, that’s a TSH of 0.35-2.0 with an absence of thyroid symptoms) combined with evidence-based breast cancer screening. I agree with the new mammogram guidelines: perform first baseline at age 50, and perform mammogram (preferably digital – less radiation) every 2 years after that. Some of my patients favor thermograms in their 40s and alternated with their mammo in their 50s+.

For my friends with greater concern, a family history of breast cancer, or a personal history of thyroid cancer followed by RAI, or just want to be aggressively preventive, another great option is to check your 2/16 ratio of estrogen metabolism. High levels of 4-hydroxy-quinone estrogen and 16-alpha-hydroxy-estrone correlates with greater risk of breast cancer. Many labs offer this test, one of my favorites is offered by Genova. Other important lifestyle factors that reduce breast cancer risk are staying lean (Body Mass Index 19-25), limiting alcohol (less than 4 x 4oz servings of wine or beer per week), and more cruciferous vegetables (brussel sprouts, broccoli and the like).

Written by, Sara Gottfried, MD

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11 Responses to “Thyroid/Breast Cancer Connection!”

  1. Caroline says:

    Very interesting. I have had both thyroid cancer in 1981 and breast cancer in 2007. I was told there was no connection between the two but it is interesting to hear of the correlation here.

    • Raquel says:

      These comments are two years old, but are very interesting considering we are still struggling trying to find answers regarding these cancers treatment and causes. I was diagnosed with breast cancer in 1994 and had a mastectomy and chemotherapy. 17 years later, I stage III cancer, and other than the usual osteoporosis , osteoarthritis, fibromyalgia, etc, I was relatively healthy with a husband, family and a full time career. I started to develop “symptoms ” apparent to me because I felt different, but not to any of my doctors because all blood tests, scans, etc were normal. Finally, a growth on my thyroid led to thyroid cancer diagnosis. I had a thyroidectomy, and the pathology report came back: thyroid cancer cells in one lymph node, and Breast cancer cells in another. So… What to do. Nobody has tried to find out what my Iodine levels , or estrogen levels (estrogen and herceptin positive ) , no one is talking about effects of synthetic hormone on breast cancer cells, etc etc. I feel lost only because there is so much information out there, but when it comes to individual situations..I cannot imagine going through chemo again, etc etc. I am meeting with my PCP next week.

  2. Thank you, Dr. G, for this enlightening article. I’ve never once heard about the thyroid/breast cancer connection, but as a thyca patient, I will definitely be looking into this a bit more.

  3. Lori says:

    Dr. G – once again, I’ve learned something valuable from your column. Thank you for taking the time to write them!

  4. Linda Payne says:

    Please advise if any studies have been done regarding non-thyroidectomies and breast cancer? I was diagnosed with Atypia Hyperplasia lump and it was removed. Now I don’t know if I should trust my surgeon’s recommendation for a follow up with an oncoligist or to go for my yearly mamo’s and let it go at that.

  5. Linda Payne says:

    Sorry, forgot to finish non-cancerous thyroid.

  6. Maria Minno says:

    My mother died of breast cancer, and that’s one reason why I have never had a mammogram, and would never get one. Mammograms CAUSE breast cancer. Thermograms are much better for detecting cancer as well as for being non-damaging.



  7. Maria Minno says:

    Iodine is truly critical to the health of the thyroid as well as breasts. In fact, iodine supports the secretory function of all glandular tissue. Iodine deficiency results in sweat glands not being able to secrete sweat, hair follicles not being able to secrete hair (hair loss), pancreas glands not being able to secrete digestive enzymes (indigestion and diabetes), the stomach not being able to secrete hydrochloric acid (resulting in further nutrient deficiencies and digestive problems, acid reflux, etc.) and thyroid glands not being able to produce or secrete thyroid hormones.

    Imagine what iodine deficiency would do to the breasts, which are giant secreting glands? The thyroid gland needs the most iodine by weight, but breast tissue is the tissue that uses iodine at the second-highest rate. As I understand it, as soon as a person takes thyroid medication, their chances of getting breast cancer increase significantly, because the iodine is pulled out of the breast and other body tissues to feed the thyroid. This may make a person feel better, but thyroid medicine is clearly not a cure. Do you know anyone who has been cured of their thyroid problems by taking thyroid medicine? Having to take a drug for the rest of your shortened life is an addiction, not a cure.

    Traditionally iodine was used to treat not only goiter, but also breast lumps and tumors. Lynne Farrow explained at a Nourishing Traditions Conference a few years ago that seaweed, which is rich in iodine, was probably the world’s first super-food or food supplement – there are prehistoric remains of seaweed stashed in dwellings that were over 100 miles from the coast, and the only transportation was by foot. That is a lot of work to get seaweed, so iodine has probably been a very important component of the human diet for many millennia, at least. Lynne and her friends have put up a very informative website that includes information and resources for iodine http://www.breastcancerchoices.org/

    For many years dairymen would use an iodine-based udder wash. This prevented mastitis and promoted lactation. The iodine would fortify the milk, so dairy products such as butter and milk were rich in the mineral. One reason we are deficient in iodine now is that we don’t get it in milk products anymore, as they primarily use some petrochemical-based udder wash instead. Iodine is known by veterinarians to treat many diseases in livestock. Why wouldn’t it be important to humans? There is actually a book written by Andre Voisin about the connection between soil health, grass health, and animal health. Voisin shows that in places where iodine was insufficient in the soil, the imbalance worked its way up the food chain to humans, and caused cancer.

    “When you don’t know what where or why: prescribe you then K and I” was an old medical school rhyme. “K” stands for potassium and “I” stands for iodine, so this meant that for symptoms that don’t add up to anything definite, give the patient potassium iodide! I hear so much complaining on this list about doctors who cannot diagnose thyroid disorers. If they just followed the old maxim, you would be in luck! Lugol’s solution, an iodine-rich preparation, was historically used for many health problems related to iodine deficiency, and all pharmacists knew how to compound it up until the 1950’s. It was considered safe until the pharmaceutical industry conducted a campaign against this important nutrient, so people would buy their drugs instead. Heart surgeons, however, still use an iodine wash to sterilize surgical wounds, because it does such a great job, and promotes healing.

    One problem with iodine supplementation now is that so many people are on low fat diets. Iodine requires fats and fat-soluble activators, particularly vitamin A, for proper incorporation of iodine into the body. In addition, the thyroid gland benefits from lauric acid, which is a fatty acid found in high amounts in coconut oil. If these nutrients aren’t plentiful, it can be difficult to absorb the iodine. The fat soluble vitamins are critical in preventing and curing autoimmune disease. This is one reason why it’s so important to have healthy fats, including plenty of saturated fats and cholesterol, in the diet during iodine supplementation (and always!).

    Fermented cod liver oil is probably the best source of essential fatty acids and the fat soluble activators. Other nutrient-dense foods for thyroid health include full-fat yogurt, creamy cheese, and butter from pastured animals. Lard, tallow, and other types of fats from organic pastured animals are critical to recovering from autoimmune disease, as well as to having healthy thyroid and adrenal glands. Liver is a fantastic source for vitamin A and minerals other than iodine needed for thyroid and overall health, but it’s important to eat it with plenty of bacon, fat, or lard from pastured animals to balance the vitamin A content with vitamin D. Caviar, especially, and also other fish eggs, and even chicken eggs provide essential fatty acids, fat soluble activators, and iodine, so no wonder caviar is so coveted a food around the world!

    Another problem with iodine supplementation is the amount of halogen toxins people are exposed to. When deficient in iodine, the halogens fluorine and bromine are similar, molecularly, and the thyroid gland and other body tissues will absorb these deadly toxins instead. These become incorporated into tissue, where they can cause disease, dysfunction, and cancer of many types. When iodine supplementation finally occurs, the tissue will throw out the toxic fluoride and bromide and absorb the iodide in its place. These toxins can cause autoimmune reactions, which I believe can lead to Grave’s and Hashimoto’s.

    Fluoride is put into toothpaste, slathered into your mouth during dental treatments, and is intentionally put into much of the drinking water throughout the US. It is also hidden, but in high amounts, in drugs, including the inhalers for asthma, the antidepressant Prozac, and the antibiotic Cipro. It is a cellular poison, between arsenic and mercury in toxicity. It is in pesticides, and therefore often found at high levels in foods, including tea, green tea, soy, lettuce, grapes and wine.

    Bromide is being used instead of iodide now as a dough conditioner in bread. It is used to fumigate produce, and is found in flame retardants and many other manufactured products. It is in Mountain Dew. It is implicated in mental illness as well as thyroid disease. A wonderful source of information on thyroid health and the link with breast cancer, iodine deficiency, and the toxin bromine, is Lynne Farrow’s website, Breast Cancer Choices at http://www.breastcancerchoices.org/

    Biochemist Dr. Galen Knight also provides information on iodine and health in the many articles that he has authored and made available on the web. Dr. David Brownstein has written two books on thyroid health and iodine. https://www.drbrownstein.com/bookstore.php

    Other medical doctors who are not afraid to work with iodine include Dr. Flechas in North Carolina http://cypress.he.net/~bigmacnc/drflechas/iodine.htm and Dr. Rind in Florida http://www.drrind.com/Home.htm Dr. Rind is quick to point out that adrenal health is critical to thyroid health, and I have found this to be so.

    Soy: Why haven’t I heard a word about it from people talking about thyroid disease? A Google Scholar search for the words “thyroid” and “soy” will pull up all sorts of articles on the damage soy has been shown to do to the thyroid gland. Soy is in nearly all processed foods. Just eliminating soy from the diet can have amazing positive effects on thyroid health. Here are some articles to start off with:

    http://www.westonaprice.org/soy-alert/266-myths-a-truths-about-soy.html Myths and Truths About Soy

    http://trit.us/soy/thyroidproblems.html Soy, the Unsuspected Cause of Thyroid Problems?

    http://www.westonaprice.org/soy-alert.html Soy Alert!

    There is a book about soy that explains its toxicity to the thyroid, called “The Whole Soy Story” by Kaayla T. Daniel, and there is even a lawsuit being filed against Illinois prisons for the “cruel and unusual punishment” of forcing inmates to eat a diet high in soy.

    Finally, thank you, Dr. Gottfried, for your informative article. I hope further articles will delve more deeply into the real major causes of thyroid disease, and examine some of the major players.

  8. Lisa Poll says:

    Very confused.
    I have had both thyroid cancer in 2010 and diagnosed with breast cancer last week. So confused… Is there any special test, treatment, medicine, pill, etc I should be telling my doctor about? I take Syntroid 175 and have anti bodies ATG all the time…


  9. Maria Minno says:

    I tried to tell you people this a couple of years ago and I got screamed off this thyroid site. There is a total connection. It starts with fibrocystic breast disease, first sign of iodine deficiency. Next is thyroid deficiency, second level sign of iodine deficiency. Next is endometriosis or other estrogen dominance issue. Finally, breast cancer, and then you die. All you have to do is take iodine and start eating a healthier diet. Get off the soy, and don’t drink fluoridated water. Halogens like fluorine and bromine and chlorinated hydrocarbons that are common in water, medicines, tea, wine, and pesticides work against iodine, so if you are exposed to these you need any more. And since Fukushima, and before that the USA aboveground nuclear testing, we’re all “downwinders” because we were exposed to radioactive iodine. At this point, with all the toxic halogen exposure and the things food processing have changed to take the iodine out of our diet, almost everyone here is severely deficient in iodine (and other minerals and nutrients). That’s what Iodoral and Lugol’s solution are for. It’s such a cheap way to prevent thyroid disorders and breast cancer. It even helps ADD and ADHD in children. Even Down’s syndrome responds positively to iodine supplementation. Check out the talks and website of David Brownstein, and the fabulous website of BreastCancerChoices.org – and don’t forget to check out the Weston A. Price foundation’s website for the most reliable information I know of on nutrition.

  10. Lisa Poll says:

    Excess iodine and thyroid cancer

    Observational studies have found increased iodine intake to be associated with an increased incidence of thyroid papillary cancer. The reasons for this association are not clear. In populations that were previously iodine deficient, salt iodization programs have resulted in relative increases in thyroid papillary cancers and relative decreases in thyroid follicular cancers. In general, thyroid papillary cancers are less aggressive and have a better prognosis than thyroid follicular cancers.

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