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Iodine for Hypothyroidism: Crucial Nutrient or Harmful Toxin?


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This article is part of a special report on Thyroid Disorders. To see the other articles in this series, click here.

In a previous article I showed why, when used alone, thyroid hormone replacement often fails. In this post I’ll explain why optimizing your iodine intake is so crucial, and why both too little and too much iodine can be harmful.

Iodine deficiency is the most common cause of hypothyroidism worldwide. Once researchers realized this, health authorities around the world began adding iodine to table salt.

This strategy was effective in correcting iodine deficiency. But it had an unanticipated—and undesired—effect. In countries where iodine has been added to table salt, the rates of autoimmune thyroid disease have risen. The following is just a sample of studies around the world demonstrating this effect:

Why does this happen? Because increased iodine intake, especially in supplement form, can increase the autoimmune attack on the thyroid. Iodine reduces the activity of an enzyme called thyroid peroxidase (TPO). TPO is required for proper thyroid hormone production.

On the other hand, restricting intake of iodine can reverse hypothyroidism. In one study, 78% of patients with Hashimoto’s regained normal thyroid function with iodine restriction alone.

However—and this is a big “however”— it appears that iodine may only pose a problem for people with Hashimoto’s and other autoimmune thyroid diseases in the presence of concurrent selenium deficiency.

In the study above where rats developed goiter while receiving excess iodine, when they were given adequate selenium they did not develop the goiter.

Other studies have shown that selenium protects against the effects of iodine toxicity and prevents the triggering and flaring of autoimmune disease that excess iodine without selenium can cause.

In my practice I always test for both iodine deficiency and Hashimoto’s when a patient presents with hypothyroid symptoms. If they are iodine deficient, I will start them on a trial of iodine and selenium together. In most cases, patients see a significant improvement. In a minority of cases, they cannot tolerate supplemental iodine even with adequate selenium intake.

Unfortunately, the blood test for iodine that your doctor might run is not very accurate. The best way to determine iodine status is with a 24-hour urine loading test. This involves taking a large dose of iodine and collecting your urine for 24 hours afterward. If you are iodine deficient, you’ll retain more of the ingested iodine than you should and the level of iodine excreted in the urine will be lower than expected. The two labs I recommend for this test are Doctor’s Data and Hakala.

That said, if your doctor or health care practitioner won’t order these tests, you can simply begin an iodine protocol. This involves starting with a low dose of iodine (I start my patients with kelp tablets that contain 325 mcg of iodine per tablet) and increasing very slowly over time. As I’ve described in this article, it’s crucial that you also take 200 mcg of selenium per day during this protocol to protect against the potentially adverse effects of iodine supplementation, especially if you have autoimmune thyroid disease.

Physicians that specialize in treating hypothyroidism with iodine (such as Dr. Abraham and Dr. Brownstein) suggest doses as high as 50 mg per day may be necessary to restore iodine levels in those that are deficient. I have used doses this high in my practice, but it’s imperative that patients build up to such high doses very slowly, and I don’t recommend doing it without the supervision of a clinician experienced with iodine treatment. Be aware that high doses of iodine can lead to a transient increase in TSH levels, which can be mistakenly interpreted as a sign of hypothyroidism.

Finally, it’s important to keep in mind that a minority of patients with Hashimoto’s confirmed by biopsy (the gold standard) never test positive for thyroid antibodies. This is probably because their immune systems are so depressed they can no longer produce antibodies. If you have a combination of hyper- and hypothyroid symptoms, I would still suspect Hashimoto’s even if your thyroid antibody tests are normal. It’s wise to be cautious with iodine if you have any signs of autoimmune thyroid disease, even without a confirmed diagnosis.

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  1. Bill, had you done a salt loading Iodine test to see if you had a deficiency?

     I wonder how many of these people who’ve experienced good results with Iodine confirmed an iodine deficiency. I’ve always asked this question….what if a hashimoto’s patient has an iodine deficiency?? Then wouldn’t they obviously need iodine supplements just as they would need vit D supps if they were vit. D deficient!?

  2. Here’s one data point: me. I’ve been severely hypothyroid for years, and diagnosed with Hashimoto’s based on antibody tests. When I supplemented with iodine (initially via daily iodine-rich sea vegetable consumption and later via 12.5 mg Ioderal daily), my requirement for thyroid hormone supplementation decreased dramatically: so far, from 165 ug T4 per day to 100 ug T4 per day and still, apparently, dropping. These dose reductions were made by my endocrinologist based on both routine TSH and Free T4 lab tests and my subjective feelings of wellness. There’s no doubt I need far less T4 medication than I did before beginning iodine.
    None of my doctors has ever seen anyone reduce their required T4 dose like this, and all agree this has to be considered a sign of improvement my illness. My endocrinologist, who did not encourage me to try iodine but reassured me it could not cause harm at these doses, is so impressed that he is considering trying iodine supplementation with other patients.
    As far as I can tell, my experience is quite consistent with what the docs most experienced with iodine supplementation (Abraham, Brownstein, and Flechas) have observed for a number of years now. They indicate that about a third of their hypothyroid patients can reduce their T4 dose, often by about half, with adequate iodine supplementation. The rest, apparently, cannot do so for some reason but stabilize and do not experience the typical need for ever-increasing doses, as I did before starting iodine. I don’t recall these docs citing any cases where autoimmune hypothyroidism got worse with iodine. And they’ve been giving iodine for years, sometimes at doses an order of magnitude greater than mine.

  3. Mario i have heard Dr. Kharrazian mention LDN as being effective. As a functional medicine practitioner, however, he largely does not go the pharmaceutical route if he doesn’t have to.
    Labrat, the teens is indeed a difficult time to introduce a gluten-free diet. However i have heard many moms say their children are less picky once they get through the transition. Picky eating is actually a symptom of food intolerances in children. I saw my own daughter’s palate really widen after we kicked dairy and gluten. It’s not easy, but many people see profound improvements as a result, so it’s worth the effort. I highly recommend you read up on pubmed or elsewhere on the connections between Hashimoto’s and gluten intolerance. Blood screens for gliadin have a very high false negative rate.

  4. Bromide exposition does not come only from bread. Far from that. Is all around any modern city, but, due it’s flammability laws, it is specially high in USA. Californian citizens have the highest exposures in the world. Bromide is in the dust, carpets, textiles, foams, electronics and plastics:
    And, for those of us in a high fat paleo diet, in USA, fat from red meat and pultry is a possible source too:
    For those on a low sodium diet, elimination of bromine, at least in rats, is dependent of sodium intake:
    Again, at least in rats, bromide can affect iodine absorption in thyroid and mammals glands:
    It can also decrease body temperature and body weight:

    Greenpeace, Chemical Footprints in Blood:
    The question is: does a good and balanced immune system is enough to get ride of all this bromide?

    A diet low in iodine, that showed to normalize TSH in that China study, will work in USA or other country with high bromide contamination?
    Dr. Datis Kharrazian doesn’t mention bromide, fluoride nor bisphenol-a on his book. At same time, Drs. Brownstein and Abraham never mention how one can improve the immune system. And neither of them mentions LDN, which is one of the best things (after a paleo diet) you can use to improve your immune system.
    So, no one have all the answers nor is 100% correct all the time.

    • That’s just what I was thinking. Perhaps all these great minds should hook up and listen to each other a little more. Put everything on the table? But even then, there’s bound to be some other variable that’s hiding in the shadows…

      • Just wanted to say I so agree too Mario. Wish I could hold a party and invite them all along to meet. You’d be invited too Chris, might need to mediate!

        I have read Dr B’s and Dr K’s books and also Dr Derry’s Iodine and breast cancer book and they are all very compelling. I swam a lot in chlorinated pools as a child so assume it must have effected me to some degree. I have also tried taking Lugols but couldn’t get up to 50, probably 20 without the area around my thyroid becoming swollen and tender and feeling like I had a huge lump in my throat. I still use Lugols topically for fibrocystic breast which works wonders (note: use a barrier oil first to stop skin irritation) but don’t know how much or how often……basically I’m dithering until the research catches up and we have more answers.

  5. Chris and Elaine

    Thank you for your input. From my perspective – stress makes sense to me as I have always felt her symptoms were more related to psycho-social issues. She is also an asynchratic gifted child. Very high intellect with suppressed emotional and social developement. She is quite eccentric and does not have much in common with her peers. I have her in counselling for executive function issues and with a gifted and talented counsellor. We have also been through a very contentious divorce in the past 4 yrs. Can you elaborate on how to support healthy pituitary function?

    Elaine – no. I’m a lab tech – I have checked her TSH regularly over the past year and it has basically remained stable. I have actually considered gluten-free but have hesitated as it would be a very difficult thing to implement. She is a very picky eater and it’s hard to find things that she will eat as it is. I did check her for anti-gliadin ab and it was negative.

    • Unfortunately the standard lab tests for gluten intolerance are insufficient.

      The literature is so clear on the connection between gluten intolerance and autoimmune thyroid that I recommend all patients with thyroid disorders avoid gluten – regardless of test results. If you want an accurate test, get the full profile from http://www.enterolab.com. Dr. Fine is a gluten researcher that has pioneered the latest, most specific methods.

      • When you say “gluten intolerance” I assume you are referring to celiac disease? I have hashi/hypo and had an intestinal biopsy but tested negative for celiac disease. I have always felt however, that while I might not be intolerant per se, that maybe I am gluten sensitive at least. What are your thoughts on gluten intolerance vs. gluten sensitivity? Same thing for all intents and purposes? Is it possible to be gluten sensitive even if you are not clinically gluten intolerant? Thanks.

    • Labrat, Have you had your daughter evaluated for Asperger’s Syndrome? : Red flag words include asynchratic gifted child, suppressed emotional and social development, eccentric, not much in common with her peers, executive function issues. If you haven’t tested her, the starting point is a developmental/ behavioral pediatrician or you can google Asperger’s psychologist in your area. (They do “psycho educational” testing, which we found to be Invaluable when dealing with school, & understanding strengths & weaknesses in our Asperger’s son. The foremost researcher in the world for Asperger’s Syndrome is Tony Atwood. He has a website & books, so if you check out his website, you will get a better idea if you should pursue testing. Many of these kids respond well to a GFCFSF diet (Gluten, casein, & soy free). I have also read about good results with a Paleo/ Primal diet. The stool test (Enterolabs) is the most accurate way to be sure if she really may have gliadin/ gluten sensitivity. Yes, big adjustment, but worth trying gluten… free.

  6. labrat, whenever you see positive TPO antibodies you are looking at Hashimoto’s, which is primarily an immune disease more so than a thyroid disease. Does her TSH fluctuate? It can swing from low to high with Hashimoto’s.
    The most important first step your daughter can take is to completely eliminate gluten from her diet. There are strong links between gluten and Hashimoto’s in many studies. A gluten-free diet is paramount. If not, she is at risk of developing autoimmune diseases against other tissues. For instance, Type I diabetes is also correlated with gluten.
    For more information, you can learn more from the book at http://www.thyroidbook.com.

  7. I’ve read Dr. Brownsteins Iodine book and as a hashimoto’s patient I tried Iodoral in the hopes it could help….this was before I read Dr. K’s book. When I first tried Iodoral at 12.5mgs I had side effects of metallic tast in my mouth and salty feeling eyes (hard to explain) When I raised to a higher dose of 50mgs this went away. I only tried this for a couple of weeks and never felt any better but no worse either….then I stopped when i started reading Dr. K’s book. I’m curious  since as you mention most hashi’s are TH1 Dominant if this could have anything to do with how some hashi’s react to iodine supplementation. I’m TH2 dominant and as I said I had no negative reaction. don’t know if there’s any correlation at all but thought i’d put it out there. Also wondering about any connection between  Gluten free diet being so important and without consuming bromide containing breads and products perhaps this helps prevent iodine from being displaced in the body? Not sure if GF products contain bromides…i’ll have to check some labels….

    • In some of the studies indicating increased autoimmune activity with iodine, the authors claim that it is more prevalent in people with a “genetic predisposition”. They’re not referring to Th1/Th2 dominance, and I can’t think of a mechanism where that would influence iodine’s effect on TPO, but I can’t rule it out either.

  8. Chris, thanks for starting this great discussion. I tried iodine last year and made it to three Idoral drops per day, but I just couldn’t take the swelling. I kept telling myself that if I continued with the regimen, the swelling would subside. At one time, I belonged to the iodine FB group and did read success stories from other thyroid patients. I tried again, and again my thyroid swelled to the point that it was difficult to swallow food.
    During my third attempt to introduce Idoral’s drops into my diet, my friend told me to stop the drops and read Dr. K’s book. I did, and decided maybe Dr. K. was right about iodine. I then gave up gluten and I am now seeing a doctor who practices Dr. K’s methods. I am taking supplements to balance my TH1 dominance. I’m feeling better than I’ve felt in a very long time.
    Neither have I read Dr. Brownstein’s book, nor have I been able to work up to 50 mgs per day. Therefore, I cannot fully comment on Dr. Brownstein’s methods. I can only comment on my limited experience with iodine and with my alternative wellness program.
    I do have a concern about lack of iodine in my diet, not for my thyroid, but for the rest of my body, especially since my grandmother died of breast cancer. I have read that iodine supplementation cuts down the risk of breast cancer.
    Any thoughts on this?
    🙂 Tamra

    • Perhaps you could try obtaining small amounts of iodine through seafood. That may not be enough to trigger an immune response, but could meet your systemic needs.

      • I took a supplement with Kelp and Alfalfa and it gave me terrible heart palps at bedtime and my face was even twitching.
        Also, after a small dose of Lithium Orotate (which increases Iodine and decreases T4/T3) I had severe anxiety and nightmares for days. Can these be hyper symptoms due to possible Hashi’s? I haven’t been diagnosed, but I have TSH .550 and normal T4/T3 with severe Hypo Symptoms. Ab neg TPO 27 ( 3 yrs ago)

  9. I just had a Genova CDSA done a month ago and had them check for H. pylori, test results were negative.  Is it smart to get a urea breath test as well to confirm?  After being on the SCD diet for over 6 months (amazing turnaround) and with the confirmation of the CDSA test my bacteria levels seem to be under control besides a very small level of Candida.  Am I missing another link in the stomach acid puzzle (nutrient deficiency, signaling pathway)?  Or after several years of SIBO I should just be patient?  Thanks!

    • Hard to say, Steve, without actually doing a full intake and exam. Sometimes H. pylori shows up on the stool test, sometimes not – and the same for the urea breath test. If I strongly suspected it, I’d do both. How do you know your stomach acid is still low? Have you had it tested, or are you going by your response to HCL?

  10. Chris much respect! Keep up the awesome work.
    Quick question in all your studies on Iodine, do you believe an iodine deficiency plays a role in inadequate stomach HCL levels?
    I don’t have any thyroid issues, however among a host of guy dysbiosis problems (SIBO, yeast) I’m correcting I have low stomach acid. I’ve been supplementing with betaine HCL for over 6 months hoping that it would correct the problem (no luck) and in some of Pro-Iodine camp literature I was reading that the parietal cells need iodine to collect chloride to make HCL.  I started supplementing with Iodine this month in hopes this might help me restore my stomach acid levels however I can’t seem to find any medical literature/studies explaining/confirming this hypothesis.  Thoughts?

    • Physiologically it’s plausible, though it isn’t discussed much in the literature. More typically hypochlorhydria is caused by bacterial overgrowth in general, and H. pylori in particular. Have you ruled out H. pylori with a urea breath test? H. pylori suppresses stomach acid production in order to create a more hospitable environment for itself.

    • Steve I had low stomach acid and have found adding One tablespoon of Apple cider vinegar (organic, with mother), in one cup or so of water, fixed me up very fast, before I could even get to the store to buy betaine HCL. I didn’t believe it would work and put it off for a while until the symptoms got so bad I couldn’t ignore them. The ACV should help with the yeast too.

    • Steve,

      Salt supplementation 1/2 teaspoon of sea salt twice a day, in water or food will help produce more stomach acid. Additionally, supplementing with large amounts of the amino-acid; “L-Glutamine” (powder preferred) is extremely helpful in healing the gut lining, stomach and intestines. Stay with a very low-carb diet with lots of cooked vegetables, bone broths, meats and organ meats too!

  11. Interesting but very confusing. If you don’t mind giving your opinion (and anyone else as well) what do you make of my daughter’s case. I am trying to make sense of it.

    16 y/o female. Likes to sleep a lot, is always cold (today was over 90 and she wore a light weight long sleeve  shirt, a long skirt and knee high boots and was comfortable – I was hot just looking at her) and is photophobic, she really hates bright light and sunshine.

    She’s been tested several times in the past year or so and her results are pretty stable.
    TSH 1.0 +/- 0.5, FT4 1.0 +/- 0.2, TG Ab negative TPO Ab 54-107.

    We’ve decided to just keep our eye on her TSH going forward – should I be worried about the low level of anti-TPO? Do you think restricting iodine would resolve it?

    • Your daughter has elevated TPO antibodies. That suggests autoimmune thyroid disease.

      Her TSH is normal from a conventional perspective (0.5 – 5.0), but low from a functional perspective (1.8 – 3.0). FT4 is also low from a functional perspective when it drops below zero. Positive TPOAbs combined with low TSH and low T4 suggests autoimmune hypothyroidism secondary to pituitary hypofunction. Chronic stress is at the root of this pattern. Stress taxes the pituitary until it can’t release enough TSH to trigger thyroid hormone production. Stress management and supporting healthy pituitary function are essential to working with this pattern.

      Keep in mind that it’s impossible to provide a diagnosis on the internet with something as complex as a thyroid condition. These are just a few ideas to consider.

    • labrat,

      Your daughters light sensitivity(photophobic) can be a sign of low aldosterone, an adrenal hormone. She may also be low cortisol as well. When the adrenals are not right, the thyroid often follows, or vice-versa.

  12. Another issue with using iodine to shut down TPO is that it doesn’t address the overall immune imbalance present in Hashimoto’s.  Studies show Hashimoto’s patients often have antibodies to other tissues in addition to the thyroid.  The best approach is to regulate the immune system so that all affected tissues are protected.

    • Thank you for all your work, Chris. I seem to have hypothyroid, because of a whole slew of symptoms that eased when I was prescribed Synthroid. I’m trying to learn what I can. Would you be so kind as to forward me your citations via email davetrindle at gmail dot com? I have also compiled a large collection of citations, and perhaps I can provide you the ones I have that are not on your list…best regards, Dave Trindle

  13. Uncle,

    That’s exactly what I advocate.  I’m happy to provide the citations.  I don’t include them all in the original articles because I don’t want to overwhelm people.

  14. Thanks for the additional citations. I am not arguing for or against a particular point, per se. I am simply asking that all crucial points be backed up by rigorous science. I’m happy to review these studies and form my own opinion, rather than just accept something.

  15. Uncle, so where are the studies to the contrary? Also, how do you account for the anecdotal evidence, of humans, of iodine making Hashimoto’s worse in people? Also, are the high doses of iodine suppressing TPO and hence the autoimmune reaction in people with Hashimoto’s? Is that how it is working? If so (because i’m not sure i totally understand the oxidation thing) then there is no argument.Also, how do you account for the study, on humans, of an iodine-restricted diet resolving Hashimoto’s symptoms in the majority of subjects? Where is the evidence that high iodine for Hashimoto’s brings cytokine and CD/CD8 levels to normal?

  16. Thanks for the reply.
    As you quoted from the first article, “Both low iodine and 100 times normal iodine intakes might activate the immune state on some degrees.”

    This study was conducted in rats. Since you apparently feel comfortable generalizing these findings to humans, do the results apply to those who are euthyroid or those with thyroid dysfunction (e.g., Hashimoto’s)? And if a person’s diet is iodine deficient, supplemental iodine in normal dosages is likely to be beneficial, correct? It would seem, based on these results, that adequate iodine in the diet is necessary, just not 100x normal amounts. But again, we are talking about a study in rats. We don’t know how this can be applied to humans, and whether we can use the results to make recommendations to those with Hashimoto’s based on this one animal study.

    Also, I noticed that the first article was in Chinese. Were you able to read the entire article, or just the abstract? I often find it necessary to review the methods and results in greater depth to accurately understand the strengths and weaknesses of the research. Unfortunately, I can’t read Chinese.

    The second article you cited is also a review article that does not provide any citations to randomized controlled trials in humans that support the statement you quoted.

    So, we are back where we started.

  17. Chris, you are doing an excellent job handling the comments – especially those that disagree. Polite, factual and concise. Thumbs up!

    • I think its important to realize and appreciate that there can be different perspectives and every body, every study, every variable is and can be different. Chris has done research as have others and I for one am thankful for the time and research. No need to get undiplomatic about Chris’ research, his perspective and or his blog. What if you or I are the 1 millionth (just an example!) person to BENEFIT from his findings. We only get more powerful with more knowledge. Thank you Chris for sharing your views.

  18. “Why does this happen? Because increased iodine intake, especially in supplement form, increases the autoimmune attack on the thyroid.”

    This citation links to an article titled Drugs and Thyroid Function published in 1995 in NEJM. It is a review article, not an empirical study. Within the article, I could not find any references to original sources that provide empirical support for the claim that increased (increased relative to what?) iodine (not iodide) in supplement form (e.g., not a side-effect of another medication) increases the autoimmune attack on the thyroid (how measured?).
    Since this is the crux of your argument, I’m sure your readers would prefer reference to randomized controlled trials rather than reviews that don’t cite original sources.

    • “Iodine might exert influence on the level of CD4/CD8, and thus the production of thyroid antibodies might directly or indirectly take part in the process of thyroid autoimmunity. Both low iodine and 100 times normal iodine intakes might activate the immune state on some degrees.”

      “It is conceivable that Tg polymorphisms, combined with the explosive mix of iodine, TPO and H2O2 necessary for thyroid hormone synthesis, inadvertently provide the trigger for the autoimmune thyroid response.”

      Also consider the study linked to indicating iodine restriction alone can induce a euthyroid state.

    • Here are a few more, some more conclusive than others:

      “In genetically predisposed individuals the iodine intake modulates autoimmune thyroid reactions. Especially with acute or chronic increase of iodine intake it leads to a significant increase in the incidence and intensity of autoimmune thyroid disease.”

      “Thyroid antibodies, both thyroglobulin (TgAb) and peroxidase (TpAb) or microsomal, were not detected in serum from patients with endemic goiter, but became positive in 43% of subjects three and six months after therapy with iodized oil, and there developed transient hyperthyroidism. Similarly, the addition of iodine to the diet or the administration of iodine-containing medications increases the frequency of ATD and the severity of existing autoimmune thyroiditis. Furthermore, autoimmune thyroiditis has been induced by the administration of excess iodide to strains of chickens and rats that are genetically predetermined to develop the disease.”

      “The best-established environmental factor is excess dietary iodine. Increased iodine consumption is strongly implicated as a trigger for thyroiditis, but only in genetically susceptible individuals.”

      “High iodine intake, selenium deficiency, pollutants such as tobacco smoke, infectious diseases such as chronic hepatitis C, and certain drugs are implicated in the development of autoimmune thyroiditis, primarily in genetically predisposed people.”

      “In our investigations, we have shown directly that T cells from humans with chronic lymphocytic thyroiditis proliferate in the presence of iodinated but not in the presence of noniodinated human thyroglobulin… if iodine is added to the drinking water, the prevalence and severity of the thyroid lesions increase markedly. The immune response is specific for thyroglobulin, both in terms of the antibody response and T-cell proliferation.”

      “A body of clinical and epidemiologic evidence points to excessive ingestion of iodine as an environmental agent. In genetically determined thyroiditis in animals, iodine enrichment has been shown to increase the incidence and severity of disease.”

      “Autoimmune thyroiditis, a model of organ-specific autoimmune disease, is associated with iodine as a precipitating environmental factor. T cells from patients with chronic thyroiditis proliferate in response to normal human thyroglobulin, but fail to react with non-iodinated thyroglobulin.”

      “A causative relationship between dietary iodine and thyroiditis has been clearly established in animal models of thyroiditis, including the NOD.H2(h4) mouse strain, which develops enhanced thyroiditis spontaneously after supplementation of drinking water with sodium iodide.”

  19. Lithium is known to depress thyroid function. When your TSH is all over it means your autoimmune thyroid condition is acting up, perhaps in response to getting off the meds. The book at thyroidbook.com addresses this autoimmune issue and what to do.