Iodine and Thyroid Health


Iodine and Thyroid Cancer Risk among Women in a Multiethnic Population
The Bay Area Thyroid Cancer Study

1. Pamela L. Horn-Ross2,
2. J. Steven Morris,
3. Marion Lee,
4. Dee W. West,
5. Alice S. Whittemore,
6. I. Ross McDougall,
7. Kent Nowels,
8. Susan L. Stewart,
9. Vickie L. Spate,
10. Amy C. Shiau and
11. Melissa R. Krone

+ Author Affiliations

Northern California Cancer Center, Union City, California 94587 [P. L. H-R., M. L., D. W. W., A. S. W., S. L. S., A. C. S., M. R. K.]; Research Reactor Facility, University of Missouri, Columbia, Missouri 65211 [J. S. M., V. L. S.]; Department of Epidemiology and Biostatistics, University of California School of Medicine, San Francisco, California 94143 [M. L.]; and Departments of Health Research and Policy [A. S. W.], Radiology and Medicine [I. R. M.], and Pathology [K. N.], Stanford University School of Medicine, Palo Alto, California 94305


Research on the relationship between iodine exposure and thyroid cancer risk is limited, and the findings are inconclusive. In most studies, fish/shellfish consumption has been used as a proxy measure of iodine exposure. The present study extends this research by quantifying dietary iodine exposure as well as incorporating a biomarker of long-term (1 year) exposure, i.e., from toenail clippings. This study is conducted in a multiethnic population with a wide variation in thyroid cancer incidence rates and substantial diversity in exposure. Women, ages 20–74, residing in the San Francisco Bay Area and diagnosed with thyroid cancer between 1995 and 1998 (1992–1998 for Asian women) were compared with women selected from the general population via random digit dialing. Interviews were conducted in six languages with 608 cases and 558 controls. The established risk factors for thyroid cancer were found to increase risk in this population: radiation to the head/neck [odds ratio (OR), 2.3; 95% confidence interval (CI), 0.97–5.5]; history of goiter/nodules (OR, 3.7; 95% CI, 2.5–5.6); and a family history of proliferative thyroid disease (OR, 2.5; 95% CI, 1.6–3.8). Contrary to our hypothesis, increased dietary iodine, most likely related to the use of multivitamin pills, was associated with a reduced risk of papillary thyroid cancer. This risk reduction was observed in “low-risk” women (i.e., women without any of the three established risk factors noted above; OR, 0.53; 95% CI, 0.33–0.85) but not in “high-risk” women, among whom a slight elevation in risk was seen (OR, 1.4; 95% CI, 0.56–3.4). However, no association with risk was observed in either group when the biomarker of exposure was evaluated. In addition, no ethnic differences in risk were observed. The authors conclude that iodine exposure appears to have, at most, a weak effect on the risk of papillary thyroid cancer.

end quote

The above is related to normal Iodine.

The US Cancer Atlas reveals those US counties with low natural Iodine counts record comparatively higher rates of Thyroid cancer. The same source shows those US counties with high natural counts also record comparatively higher rates of Thyroid cancer.

Long term dietary Iodine intake is one factor among many which determines vulnerability to thyroid cancer. As there seems to be a middle band of Iodine intake that is optimal, it is surprising that long term additional Iodine provided by regular use of vitamin/mineral supplements show a reduction in risk in the above paper.

The following article, which is not academic and which is not adequately referenced, is a guide to other risk factors associated with thyroid cancer. Suffice to say, unqualified long term boosting of Iodine by way of supplements is probably a benefit in the context of iodine deprived diets. Such long term boosting of Iodine in the context of optimal and higher than optimal natural Iodine dietary uptake seems to present as a possible risk – but that’s just my opinion. Lesson is not to artificially boost long term dietary Iodine without first getting fully qualified medical clearance to do so.

Its a complicated thing. One cannot just fiddle about with long term Iodine uptake and expect a benefit. It might present additional risk to individuals.

The emergency response of very short term boosting of natural Iodine uptake to minimise uptake of radioactive Iodine in Japan should not be resisted.

BUT : If such a measure extended into longer term administration in the context of long term contamination of the biosphere by Radio Iodine, the protection may in actual fact add, rather than subtract from, the cancer risk of the population in question. Further, individuals vary. It can be expected that the long term optimal daily intake of Iodine for individuals will vary. A long term protective dose for one person may present a risk factor for another.


Thyroid Disease 101
Basic Information on Hypothyroidism, Hyperthyroidism, Nodules, Cancer

By Mary Shomon, Guide

Updated June 19, 2006

An estimated 27 million Americans have thyroid disease, and more than half are undiagnosed. Frequently misunderstood, and too often overlooked and misdiagnosed, thyroid disease affects almost every aspect of health, so understanding more about the thyroid, and the symptoms that occur when something goes wrong with this small gland, can help you protect or regain good health.

Women are at the greatest risk, developing thyroid problems seven times more often than men. A woman faces as high as a one in five chance of developing thyroid problems during her lifetime, a risk that increases with age and for those with a family history of thyroid problems.

Where is the Thyroid and What Does it Do?

Your thyroid is a small bowtie or butterfly-shaped gland, located in your neck, wrapped around the windpipe, behind and below the Adam’s Apple area. The thyroid produces several hormones, of which two are key: triiodothyronine (T3) and thyroxine (T4). These hormones help oxygen get into cells, and make your thyroid the master gland of metabolism.

The thyroid has the only cells in the body capable of absorbing iodine. The thyroid takes in iodine, obtained through food, iodized salt, or supplements, and combines it with the amino acid tyrosine. The thyroid then converts the iodine/tyrosine into the hormones T3 and T4. The “3” and the “4” refer to the number of iodine molecules in each thyroid hormone molecule.

When it’s in good condition, of all the hormone produced by your thyroid, 80% will be T4 and 20% T3. T3 is considered the biologically more active hormone — the one that actually functions at the cellular level — and is also considered several times stronger than T4.

Once released by the thyroid, the T3 and T4 travel through the bloodstream. The purpose is to help cells convert oxygen and calories into energy.

As mentioned, the thyroid produces some T3. But the rest of the T3 needed by the body is actually formed from the mostly inactive T4 by a process sometimes referred to as “T4 to T3 conversion.” This conversion of T4 to T3 can take place in some organs other than the thyroid, including the hypothalamus, a part of your brain.

The thyroid is part of a huge feedback process. The hypothalamus in the brain releases Thyrotropin-releasing Hormone (TRH). The release of TRH tells the pituitary gland to release Thyroid Stimulating Hormone (TSH). This TSH, circulating in your bloodstream, is what tells the thyroid to make thyroid hormones and release them into your bloodstream.

Causes of Thyroid Disease

What causes thyroid problems? There are a variety of factors that can contribute to the development of thyroid problems:

* Exposure to radiation, such as occurred after the Chernobyl nuclear accident
* Overconsumption of isoflavone-intensive soy products, such as soy protein, capsules, and powders
* Some drugs, such as lithium and the heart drug cordarone, can cause hypothyroidism.
* An overconsumption or shortage of iodine in the diet can also trigger some thyroid problems. (This also applies to iodine-containing supplements, such as kelp and bladderwrack.)
* Radiation treatment to my head, neck or chest. Radiation treatment for tonsils, adenoids, lymph nodes, thymus gland problems, or acne
* “Nasal Radium Therapy,” which took place during the 1940s through 1960s, as a treatment for tonsillitis, colds and other ailments, or as a military submariner and/or pilot who had trouble with drastic changes in pressure
* Overconsumption of uncooked “goitrogenic” foods, such as brussels sprouts, broccoli, rutabaga, turnips, kohlrabi, radishes, cauliflower, African cassava, millet, babassu, cabbage and kale
* Surgical treatments for thyroid cancer, goiter, or nodules, in which all or part of the thyroid is removed, leave you hypothyroid
* Radioactive iodine treatment (RAI) for Graves’ disease and hyperthyroidism typically leave patients hypothyroid

You have a higher risk of developing thyroid disease if, among a variety of factors:

…You have a family member with a thyroid problem
…You have another pituitary or endocrine disease
…You or a family member have another autoimmune disease
…You’ve been diagnosed with Chronic Fatigue Syndrome
…You’ve been diagnosed with Fibromyalgia
…You’re female
…You’re over 60
…You’ve just had a baby
…You’re near menopause or menopausal
…You’re a smoker
…You’ve been exposed to radiation
…You’ve been treated with lithium
…You’ve been exposed to certain chemicals (i.e., perchlorate, fluoride)

end quote. Extract only. Its just an article on the net without any peer review that’s obvious. Just a guide.

In short, it may well be counterproductive for well fed people to fiddle about with Iodine supplements long term.
The US Cancer Atlas data tends to indicate both a relative lacking and a relative boosting of Iodine beyond – an optimal middle range – are risk factors for cancer.

It may well be that the findings of Horn-Ross et al (1. above) result from a total survery population who experience a less than optimal level of dietary Iodine. (ie the Bay Area of San Fransico.) ie Horn-Ross et al are surprised to find iodine boosting by way of vitamin tablets reduced Thyroid cancer risk in the survey.

Think carefully if you are tempted to copy Iodine boosting merely because you have seen it on TV re Japan.

4 Responses to “Iodine and Thyroid Health”

  1. Role of Acomplia in Weight Loss - 减肥 Says:

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  3. go to website Says:

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    • nuclearhistory Says:

      I remember from looking at the problem of thyroid disease in relation to the nuclear test era that too high as well as too low an iodine intake can result in increased thyroid cancer. And that was stable Iodine. So don’t make changes in your iodine uptake without talking to your doctor everyone, please.

      I it seems to me that in the course of fighting the effects of radiation in the body, the endocrine system is stressed. And that includes the thyroid gland. There are two vectors here: 1. Iodine 131 going to the thyroid, giving increased dose to that gland. 2. The extra work the thyroid does when the body responds to the effects of radiation throughout the body. That’s my opinion. The rate of endocrine and hormonal illness among Downwinders in Nevada and Utah is apparently quite high, especially among women.

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