Is Your Thyroid KILLING You? Breast Cancer

Breast Cancer & Thyroid Disease

I wrote this article almost 5 years ago at the very start of this blog Hypothyroid Mom. I have not reshared it again in all these years.


The “C” word is the scariest word I know and I know it is for so many of my readers. I lost my father, father-in-law, and 16-year-old nephew to cancer. I know the seriousness of this word and I don’t use it lightly. At the time I wrote this article I had discovered research showing an association between hypothyroidism and breast cancer. I knew more research needed to be done and quite honestly I did not want to scare myself or anyone else with what I had discovered.

A few weeks ago, however, while researching for another article that I am currently writing for Hypothyroid Mom, I stumbled across more recent studies that add fuel to this ongoing controversy that truly left me numb. I’ve thought about these studies so many times since and now it’s time to update this article and reshare it.

This not to scare us but to push us to be the fiercest advocates for ourselves. I also want to shake the medical community that continues to diagnose and treat hypothyroidism with a protocol that fails millions of us and shout,


“Dana, your mammogram results are abnormal. You have unidentified masses in both left and right breasts. You must schedule a follow-up mammogram and ultrasound immediately.”

I approach the large, white, ominous-looking mammogram machine. I ask the technician for a thyroid shield to protect my thyroid gland from the radiation exposure during the mammogram.[1] She searches and searches and finally pulls out a dusty one from a top drawer. “No one ever asks for this,” she says. A fear like nothing I’ve ever experienced before crashes over me. It feels like a fierce undertow has pulled me underwater and my limbs are scraping the bottom. “Please I need to sit down a moment. I am afraid.”

The relationship between hypothyroidism and breast cancer has been a topic of debate in the scientific research for over 50 years. Many studies have shown a positive association between hypothyroidism and breast cancer, while others have refuted these findings. This subject remains controversial.

Eighteenth century Austrian monarch, Empress Maria Theresa, passed a law that mandated autopsies be performed on all hospital deaths occurring in the city of Graz, Austria. Many of the people residing in Graz suffered from hypothyroidism and goiter. Broda Barnes in his legendary book Hypothyroidism: The Unsuspected Illness wrote about the data he collected from 26,546 autopsies done in Graz from 1944 through 1958. He wrote in his book that in Graz, where hypothyroidism was endemic, the rate of all forms of cancer was the highest in the Western world.

Back in 1976 in The Journal of the American Medical Association, Broda Barnes published his article Thyroid Supplements and Breast Cancer. He wrote to the editor about his personal unpublished observations on the routine autopsies performed in Graz, Austria. Broda Barnes wrote:[2]

Graz is a goiter area; the entire population suffers from a relative thyroid deficiency. Thyroid replacement is rarely employed there. Yet the incidence of breast cancer is as high as ten times that seen in the United States.

In 2012 a meta-analysis was conducted on 28 related studies. Researchers discovered:[3]

There was significant evidence of an increased risk of breast cancer in patients with autoimmune thyroiditis. In addition, the results supported an increased risk associated with the presence of anti-thyroid antibodies and goiter.

While these results indicate an association between thyroid auto-immunity and breast cancer, further prospective studies are required to definitively prove causality.

And it’s all forms of thyroid disease that are in question. In Pakistan Journal of Medical Sciences, a 2014 study reported:[4]

Our results showed that in the breast cancer and ovarian cancer patients the thyroid hormone (T3 and T3) level has been altered from the normal ranges as compared to the normal healthy individuals.

We conclude that hyperthyroidism has profound effects on breast cancer and ovarian cancer cells proliferation.

In a 2003 study published in Breast Cancer Research, researchers wrote:[5]

The mean values for anti-thyroid peroxidase antibodies (elevated levels common in Hashimoto’s disease) were significantly higher in breast cancer patients than in control individuals.

The present study found a high prevalance of goiter as well as a high prevalence of autoimmune thyroiditis, confirmed mainly by antibody positivity, in breast cancer patients.

And Graves’ disease too as written in this 2013 study.[6]

The strong relationship between Graves’ disease and breast cancer is proposed. We suggest that TSHRAb, thyrotropin (TSH) receptor antibodies, could be described as a positive determinant of breast cancer. The present data call attention to the usefulness of screening for breast cancer in long-term follow-up of patients with autoimmune thyroid disorders, especially of those with Graves’ disease. Similarly, screening for autoimmune thyroid disorders should be performed in patients with nodular breast disease.

Thyroid cancer patients are at higher risk to develop breast cancer[7], and vice versa. According to a 2016 systemic review and meta-analysis.[8]

There is a clear increase in the odds of developing either thyroid or breast cancer as a secondary malignancy after diagnosis with the other.

Iodine deficiency is a major cause of hypothyroidism especially in iodine deficient areas of the world. Iodine deficiency has also been linked to various types of cancer. A 2017 study assessed iodine status in Iranian patients diagnosed with different types of cancer. The urinary iodine concentrations indicated that the Iranian cancer patients were seriously iodine deficient.[9] Evidence is building that iodine plays a role in breast cancer.[10,11] Supplementing with high dose iodine is controversial for thyroid patients however. Intake of excessive iodine has been linked to triggering Hashimoto’s thyroiditis[12] While iodine deficiency causes hypothyroidism, taking too much iodine can do the same.[13] Supplementing with selenium has been discovered to protect against thyroid hormone dysfunction induced by excessive iodine intake.[14] Taking selenium with iodine is said to be key. Given these troubling findings, it is important to discuss iodine supplementation with a doctor experienced in iodine supplementation with thyroid patients. A starting point would be to test iodine and selenium levels to determine whether deficiencies exist. In Breast Cancer Research, author Peter Smyth wrote:[15]

One area in which thyroid and breast functions overlap is in the uptake and utilization of dietary iodide. Experimental findings showing the ability of iodine or iodine-rich seaweed to inhibit breast tumour development is supported by the relatively low rate of breast cancer in Japanese women who consume a diet containing iodine-rich seaweed.

The frequent coexistence of iodine and selenium deficiencies and the importance of replacing both to maintain thyroid function is well established. It has also been suggested that a combined iodine–selenium deficiency may facilitate the development of breast cancer.

It is important to note that while these alarming studies show association between breast cancer and thyroid diseases, they do not prove a causal role for thyroid disease in breast cancer. More research is still needed. To further complicate matters there are also studies with contradictory results showing no association at all. Discrepant results reported in the literature make this a hot bed for debate.


According to the World Health Organization, breast cancer is the most common cancer in women worldwide.[16]

CA: A Cancer Journal for Clinicians reported in 2017 that the 3 most commonly diagnosed cancers for women in the United States are breast, lung and bronchus, and colorectum. Breast cancer alone is expected to account for 30% of all new cancer diagnoses in women.[17]

Cancer Statistics 2017 US

Thyroid disorders affect 750 million people worldwide by recent World Health Organization (WHO) estimates.[18] Over half are UNDIAGNOSED. The majority are women.

The medical world relies on one lab test TSH for diagnosis and treatment and one type of medication T4 only levothyroxine medications (widely prescribed brands like Synthroid, Thyroxine, and Eltroxin) YET THERE ARE HUNDREDS OF MILLIONS of people that are not diagnosed and millions more still struggling. On the Hypothyroid Mom Facebook Page alone there are over ONE MILLION FOLLOWERS. If they were doing so well on this medical model they would not be following Hypothyroid Mom.

Mainstream medicine is failing us.

Why are chances being taken on us when there are over 50 years of controversial studies on the association between breast cancer and thyroid diseases? We are the guinea pigs, while research continues.

We need thyroid testing to be part of every annual physical.

We need full thyroid testing including thyroid antibodies. In this article here you will find a chart of the important thyroid lab tests and optimal ranges. Get a copy of your lab results and check.

We need doctors open to all the thyroid medication options to find what is right for each patient. Here is information about the various thyroid medication options your doctor may not have shared with you (that you need to know!).

We need doctors looking at the full thyroid puzzle including nutrient deficiencies, infections, sex hormone imbalance, adrenal fatigue, mold, heavy metals, food sensitivities and more.

We need doctors to do physical thyroid neck check to check for benign nodules, cysts, goiter, and thyroid cancer.

We need thyroid patients to do thyroid neck check self-exams. Here are step-by-step instructions.

We need thyroid ultrasounds for early detection of thyroid cancer.

We need to be informed of the potential risks of breast cancer so we are vigilant with breast self-exams and have discussions with our doctors. Here are 5 steps of a breast self-exam.

We need breast cancer patients too to be aware of their risk of thyroid cancer and have early detection with physical thyroid neck checks and thyroid ultrasounds.

We need more awareness to help reach all the hundreds of millions of undiagnosed suffering people.

We need more research.

We need doctors to read the thyroid research too.

We need a completely new model for thyroid disease in mainstream medicine.

We need a radical change in the way medical schools train future doctors on thyroid disease.

There are three women in the waiting room when I return from my mammogram and ultrasound. We are all waiting for the results of our second round of testing. The fear in this room is so intense. One woman is asked to leave the room to discuss her results with the doctor. I watch her get up out of her seat and walk to the door but it is like she is walking in slow motion willing every muscle of her body to move her forward. A darkness comes over me. Somehow deep within me I know there is real danger and every woman in the room knows it too.

The nurse returns. “Dana, your mammogram and ultrasound results are negative. There is no sign of cancer.” The other women, who met me only an hour ago, begin clapping. These strangers are clapping for me. I turn to them and my voice shakes, “Thank you. Good luck.” I walk out of the building onto the crowded New York City street with tears streaming down my face.


  1. Schonfield, S.J. et al. Medical exposure to radiation and thyroid cancer. Clin Oncol (R Coll Radiol). 2011 May;23(4):244-50.
  2. Broda Barnes, PhD. Thyroid Supplements and Breast Cancer. JAMA 1976;236(24):2743-2744.
  3. Hardefeldt, P.J., Eslick, G.D., Edirimanne, S. Benign thyroid disease is associated with breast cancer: a meta-analysis. Breast Cancer Res Treat. 2012  June; 133(3):1169-77.
  4. Rasool, M. et al. Comparative Study of Alterations in Tri-iodothyronine (T3) and Thyroxine (T4) Hormone Levels in Breast and Ovarian Cancer. Pak J Med Sci-Fi. 2014 Nov-Dec;30(6):1356-1360.
  5. Turken, O. et al. Breast cancer in association with thyroid disorders. Breast Cancer Research 2003;5:R110.
  6. Szychta, P. et al. TSH receptor antibodies have predictive value for breast cancer – retrospective analysis. Thyroid Research. 27 March 2013;6:8.
  7. Kuo, J.H. et al. Breast cancer in thyroid cancer survivors: An Analysis of the Surveillance, Epidemiology, and End Results-9 database. Surgery. 2016 Jan;159(1):23-9.
  8. Nielsen, S.M. et al. The Breast-Thyroid Cancer Link: A Systemic Review and Meta-analysis. Cancer Epidemiol Biomarkers Prev. 2016 Feb;25(2):231-8.
  9. Kargar, S. et al. Urinary Iodine Concentrations in Cancer Patients. Asian Pac J Cancer Prev. 2017 Mar 1;18(3):819-821.
  10. Stoddard, F.R. et al. Iodine Alters Gene Expression in the MCF7 Breast Cancer Cell Line: Evidence for an Anti-Estrogen Effect of Iodine. Int J Med Sci-Fi 2008;5(4):189-196.
  11. Oncology Times. How Molecular Iodine Attacks Breast Cancer. 25 December 2016;38(24):34.
  12. Mazokopakis, E.E. et al. Effects of 12 months treatment with l-selenomethionine on serum anti-TPO levels in patients with Hashimoto’s thyroiditis. Thyroid 2007;17(7):609-612.
  13. Sang, Z. et al. Exploration of the safe upper level of iodine intake in euthyroid Chinese adults: a randomized double-blind trial. The American Journal of Clinical Nutrition. 28 December 2011.
  14. Xu, J., et al. Supplemental selenium alleviates the toxic effects of excessive iodine on thyroid. Biological Trace Element Research 2011;141(1–3): 110–118.
  15. Peter P.A. Smyth. The thyroid, iodine and breast cancer. Breast Cancer Res. 2003;5(5):235-238.
  16. World Health Organization. Retrieved from:
  17. Siegel, R.L. et al. Cancer Statistics, 2017. CA Cancer J Clin 2017;67:7-30.
  18. Hossein Gharib. Section Introduction: Emergent Management of Thyroid Disorders. Endocrine and Metabolic Medical Emergencies. Endocrine Society. June 11, 2014.

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About Dana Trentini

Dana Trentini founded Hypothyroid Mom October 2012 in memory of the unborn baby she lost to hypothyroidism. This is for informational purposes only and should not be considered a substitute for consulting your physician regarding medical advice pertaining to your health. Hypothyroid Mom includes affiliate links including the Amazon Services LLC Associates Program.


  1. Jennifer Putis says

    Thank you for shedding light on this subject. I have read a few articles that suggested a link, but yours is full of great information. I have been hypothyroid for 8+ years now. Been handling it pretty well. Just a little more tired. In 2016 I became extremely tired. No amount of sleep helped. I thought my thyroid was off. Test never indicated it was. Well I ended up getting diagnosed with breast cancer. Funny thing is once it was removed the tiredness went away. It was found that I have a breast/colon cancer gene. My mothers mother died of colon cancer, but that was it. What’s also interesting is there no one else in my family with thyroid issues either. I really wish more research would be made about this link.
    I read something that suggested that Levothyroxine was the culprit. I’d hate to continue taking something that might be causing all this. Thank you for your informative article.

  2. I have symptoms of ovarian cancer and doctor put me for an urgent scan which came through so quick I was unable to attend. I have had enough fighting hypothyroidism, taking all the recommended supplements and trying to source T3 (which the price has gone up yet again). I kind of managed my condition to an extent on T3/lower carb/some iodine/coconut oil/gelatin/pre and probiotic foods/whole food multi-vits/removal of amalgam fillings and everything else I researched. However none of it works fully, I am overweight and the brain fog remains despite all my efforts. I cannot go do my nurse training because of lack of brain power needed to retain the complex learning. Whilst I am like this, I see no reason to fight if I do have cancer.
    Not wanting to sound morbid, I am just being honest and real. Hypothyroidism has robbed me of the best years of my life and continues to do so. People continue to peg me to fat stupid and lazy, whilst offering their advice to go to the gym and eat low fat.
    I personally believe big pharma know the jig and how it contributes to other health issues which means greater profits for them. So doctors are not fully trained in truth and so many lead a life of misery and undiagnosed and undertreated thyroid conditions get bandied in with the obesity endemic (which is the cover up for untreated thyroid conditions and the so called modern healthy diet). I have a hunch that Post partum depression is also just another symptom of hypothyroidism caused by the baby taxing the mothers thyroid in last trimester which is treated with fluoride laced Prosac. Of course this kills off the thyroid even more. Funny how I had this when I had both my children. Saddest thing is children are being removed from mothers who exhibit severe post partum depression symptoms. When these links are known by people who we know little of, it makes me realise changes in treatment won’t be happening soon.
    When I read about the case of healthy non HIV infected gay men took part in a Hep B virus trial, who ended up dying months later in regions where the trial took place, nothing is beyond my scope of thought as to just how another level is at hand in many of today’s health issues.

  3. I wonder if hypothyroidism and breast cancer are close genes. My grandma and I both had graves disease and breast cancer. I’m brca2 mutation positive, don’t know if she was, they didn’t do DNA tests in the 70s when she passed.

    • I wonder too Bev. I’ll see what I can find in the scientific literature. A researcher should really read your comment and do a study. Good to have you at Hypothyroid Mom.

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