This website is dedicated to the millions of thyroid patients who are being ignored and left to suffer unnecessarily, and to healthcare practitioners, who want to better serve those patients.

Hypothyroidism and Cancer

Supplementary memorandum submitted by Kathy Page
INTRODUCTION As a member of BREAST UK I am a patient advocate. I am a retired biomedical scientist with personal experience of both breast cancer and hypothyroidism. Looking at the research into both diseases, it soon becomes evident that there is a link between all cancers and hypothyroidism.

In fact, if hypothyroidism were taken seriously, not only would much cancer be PREVENTED and outcomes in treatment be improved, but other ailments such as ME and heart disease would also benefit. This would save the NHS a great deal of money in a relatively short time.

The following is an overview of some of the literature illustrating how low thyroid is implicated in cancer, and how equivocal blood test results have let patients down and made some existing research unclear.

The purpose of this memorandum is to bring to your attention the link between hypothyroidism and cancer with the hope that more research will follow, leading to improved patient outcomes.


1.1 This is an old book but it tells how people suffer for years without being properly diagnosed and are then treated with synthetic hormone that doesn’t always work. The sin is that it is all still relevant today. His theories are backed with research. He realised that hypothyroidism is associated with atherosclerosis, heart disease, diabetes and cancer.(Ref:1)

1.2 Every cell in the body needs thyroid hormone, therefore, every cell will feel the effects of deficiency. Which systems develop symptoms first depends on individual strengths and weaknesses.’ This sheet explains how the thyroid controls metabolismthe energy needed in every cell to function properly. With lower body temperatures all the enzymes work more sluggishly.


2.1 Broda Barnes’s theory is that, whereas low thyroid people would have died from infections, especially TB, with the introduction of antibiotics they were now surviving and reproducing. Hypothyroidism runs in families.

2.2 Richard M Alford MD says that the cause is the failure to treat maternal hypothyroidism during pregnancy. The foetus supplements the maternal deficiency from about the fifth month and the child is born deficient. Like Broda Barnes he attributes many diseases and problems to hypothyroidism. “Those with very poor metabolic function will die very young on average in spite of their genes. The optimal thriving condition in an euthyroid individual increases their capability to suppress the effects of their abnormal genes”. (Ref: 3)

2.3 Environmental hormone disrupters, find their way into our bodiesmimic the shape of the real hormone and block the receptor site.(Ref: 4)

  • “In many instances, specific hormones and the biological processes they control are chemically identical in animals and humans,” and “this means that a chemical which affects the same component of the endocrine system of an insect can be expected to similarly affect a mammal”.

2.4 The EU Commission is gathering evidence to identify a list of 100 potential endocrine disrupting substances. Report due in April 2000. Particular reference to herbal oestrogens, phthalates used in plastics and pesticides.

2.5 Dr Durrant-Peatfield lists a number of chemical agents that interfere with the manufacture of thyroid hormone. Chemicals in paints & wood preservatives, plastics, some vegetables, cigarette smoke, caffeine, aspirin and fluorides etc. (Fluoride is added to some water supplies!)(Ref: 5)

2.6 Selenium is a dietary supplement recommended for cancer prevention. Areas of naturally high selenium intake, like Japan, have lower breast cancer mortality. Selenium is a component of the enzyme that is needed to convert Thyroxine T4 into T3 which can then be used by individual cells in the body.(Ref: 6)


3.1 Study by the Institutes of Endocrinology and Pathology, University of Pisa, Italy. This study examined breast cancer patients, before starting any therapies, all from an iodine sufficient area. Thyroid disease was present in 46 per cent of breast cancer patients and in 14 per cent of controls. (This was using the less sensitive lab tests!)(Ref: 7)

3.2 An article in the Lancet in 1974(Ref: 8).

This study showed that a large number of patients with breast cancer have sub-optimal level of thyroid activity which is not secondary to pituitary or hypothalamic disease. Areas where endemic goitre is uncommon have a low breast cancer mortality and it is increased in areas where it is common. Low thyroid in breast cancer has an adverse effect of prognosis, and thyroidectomy performed on patients with apparently stable breast cancer can cause sudden dissemination of the disease. The above report suggests a causal relationship between thyroid dysfunction and breast cancer.

3.3 Another article in the Lancet in 1974(Ref: 9).

Hypothesis based on previous experimental evidence that a sub-optimal level of circulating thyroid hormones may abnormally sensitise mammary epithelial cells to prolactin stimulation, leading to dysplasia and eventual neoplasia. It is also possible that with sub-optimal levels of thyroid hormones, prolactin initiates malignant transformation in cells unprimed for mammotrophic stimulation, probably in the presence of optimal concentrations of growth hormone and ovarian steroids. Plasma prolactin levels in patients with early or advanced breast cancer are normal but TSH (Thyroid Stimulating Hormone) is significantly raised.


4.1 A study in Japan found that the patients whose disease progressed, showed significantly lower T3 levels and higher TSH, and their tumours were resistant to subsequent therapies. Prolactin levels were higher in the “progressive disease” and “no change” groups compared to “partial response” group.(Ref: 13).

5.1 A study showing concerns about radiogenic effects of irradiation outside the treated area. It measured the scattered dose to contra-lateral breast, thyroid and gonads.(Ref: 10).

5.2 Breast cancer patients near Chernobyl, demonstrated significant disturbances in function of hypophyseal-thyroid and hypophyseal-adrenal axes. These may effect prolactin secretion, which worsens the prognosis.(Ref: 11).

5.3 Hypothyroidism & Tamoxifen

Symptoms are the same as the side effects attributed to Tamoxifen, and cause many people to stop using Tamoxifen. It would be logical to screen all breast cancer patients for hypothyroidism as part of their adjuvant therapy. Perhaps more patients would then stay on the regime or would not suffer these distressing symptoms. Tamoxifen also influences thyroid hormone levels by modulating plasma TBG (thyroid binding globulin) & by interfering with hormone synthesis or secretion in the thyroid gland.(Ref: 12).

5.4 Low basal temperatures mean that all the hormones are not working at optimal temperature. This must affect the blocking reaction of tamoxifen and oestrogen, rendering it less effective.


Dealing with interpretation difficulties.(Ref: 14)

6.1 Blood tested by the laboratory can only give a snapshot in time. It varies in response to cold or illness. Levels are greater in the early morning and lower in the evening. There is also a day to day cyclical variation.

6.2 The tests:

Total T4measures circulating thyroxine. Does not show how utilised in the body.
T3 uptakeis only an estimate of sites not taken up by T4 and has only a 50-60 per cent sensitivity for hypothyroid states.

TSH(Thyroid Stimulating Hormone) measures pituitary response to circulating T3 & T4. A sensitive TSH test is available. There is diurnal variation.

Free T4a better assessment of thyrometabolic rate than total T4.

  • Total T3the active form of the hormone. More useful to indicate hyperthyroidism as the test is more accurate at the higher levels.

6.3 Thyroid hormone available in the blood stream may not reach proper equilibrium with the extra-cellular fluid and cells. The body will attempt to maintain blood levels within certain ranges no matter what is occurring at the cellular level. Physicians should bear in mind the variables in the time that the sample is taken. Laboratory error and different testing methods add further variations.

6.4 Reference ranges are determined from a wide population. Patients who are marginally ill may fall within the range and so are missed. Lab tests should not be used to make a diagnosis, but to substantiate clinical signs and symptoms. The patients optimal range should be found rather than basing on population studies. Other medications may affect some patients in regulating thyroid supplementation.

6.5 Basal Body Temperatureas advocated by Broda Barnes MD.(Ref: 1, 2, 5, 14)

A more sensitive indicator of hypothyroidism than blood testing. It gives an indication of what is occurring during optimal thyroid output rather than a random blood draw. It gives a better indication of what is occurring at the cellular level by measuring the body’s metabolic response.
June 2000

1. Hypothyroidism, The Unsuspected Illness. By Broda O Barnes MD and Lawrence Galton. ISBN 0-690-01029-X have reviews.
2. Your Thyroid. Broda O Barnes M.D. Research Foundation Inc.
3. Richard M Alford MDLow Metabolism or Hypothyroidism.
4. Environmental Estrogens. The Endocrine System & Endocrine Disruptor News. How Endocrine Disrupters Work.
5. ArticleSuggestions for an approach to the management of thyroid deficiency. Dr Durrant-Peatfield.
6. ArticleRichard A Passwater, Ph.D. New discoveries expand our knowledge about selinium’s importance.
7. The Journal of Clinical Endocrinology & Metabolism. Vol 81, No. 3, pp. 990-994 March 1996. Study by the Institutes of Endocrinology and Pathology, University of Pisa, Italy.
8. The Lancet 11 May 1974. Hypothalmic-Pituitary-Thyroid axis in Breast Cancer. I Mittra & J L Hayward, Imperial Cancer Research Fund Breast Cancer Unit. Guy’s Hospital, London.
9. The Lancet 11 May 1974. Hypothalmic-Pituitary-Prolactin axis in Breast Cancer. I Mittra, J L Hayward, Imperial Cancer Research Fund Breast Cancer Unit, Guy’s Hospital & A S McNeilly, St Bartholomew’s Hospital, London SE1 9RT
10. ArticleAn in-vivo dosimetric study of the scattered radiation during the treatment of breast carcinoma. Radiologia Medica 91(1-2):122-5, 1996 Jan-Feb.
11. ArticleThe functional status of the hypophyseal-thyroid and hypophyseal-adrenal systems in breast cancer patients taking into account their exposure to the factors of the accident at the Chernobyl Atomic Electric Power Station. Likarska Sprava. (5-6); 29-31, 1995 May-June.
12. ArticleThyroid function in post menopausal breast cancer patients treated with Tamoxifen. Scandinavian Journal of Clinical & Laboratory Investigation. 58(2):103-7 April 1998
13. Relationship between thyroid-pituitary function and response to therapy in patients with recurrent breast cancer. 1996 July-August, Gunma University School of Medicine, Japan.
14. Journal of Naturopathic Medicine. Thyroid Function Testing: Dealing with Interpretation Difficulties.


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