If you discover you have a hot nodule, then prepare to become obsessed with your iodine intake.

The iodine connection

Iodine supply is the only aspect of a toxic nodule’s production of excess hormone that is in your control, and you can’t afford to ignore it. No other dietary constituent will have nearly as much power to determine the quality of how you feel.

People with normal thyroids have the luxury of knowing their pituitary gland will help regulate how their thyroids handle variations in iodine ingestion. Meanwhile, many with autoimmune hypothyroid conditions will advocate for large doses of iodine to “stimulate” a sluggish gland. Even some with autoimmune hyperthyroidism may be given excessive doses of iodine, which is well-known to temporarily slow down thyroid hormone production in an adaptive response known the Wolff-Chaikoff effect. callout 1This effect can still be somewhat relied on in “early” thyroid autonomy, at least in one study I found (S7), and experiments showed that excess iodine can be “suppressive to autonomous thyrocyte proliferation.”

But someone with a long-standing hyperfunctioning nodule can no longer rely on internal systemic controls – whether from the pituitary or the Wolff-Chaikoff effect. An autonomous nodule reacts unpredictably, marching to the beat of its own drummer, and if it finds iodine available, it is likely to take it up, store it, and industriously produce thyroid hormone just as fast as it can. (See How Thyroid Hormone is Produced)

Now, as important as iodine levels are with a hot nodule, one might think endocrinologists would be quick to proffer guidelines and warnings about iodine intake to their patients with a toxic adenoma. But many, maybe even most, do not. Mine certainly didn’t. In fact, when I specifically asked if I should be thinking about limiting iodine since my symptoms had exploded a few months after switching to iodized salt, my doctor waved a dismissive hand and said there was no way the iodine in salt could have caused my sudden drop in TSH. He also said I didn’t need to worry about iodine in my food. “Just eat regular amounts,” he said. He did not specify what that a “regular amount” might be.

Then I went home and did a search on PubMed and found study after study that confirmed that even seemingly small increases in iodine can cause considerable increases in thyroid hormone in someone with an autonomous nodule (or even occasionally without one). This is known as the Jod-Basedow Effect, named after the German word for iodine (Jod) and the German physician Karl Von Basedow, one of the first to describe the symptoms of hyperthyroidism.

The Jod Basedow effect: hot nodule meet iodine

Dr. Von Basedow, working in the mid 19th-century, did not of course discover the contribution of hot nodules or toxic adenomas to hyperthyroidism; that would be left to Dr. Emil Goetsch in 1918. But while Dr. Von Basedow believed iodine could helpful for his autoimmune hyperthyroid patients (as it sometimes is in Grave’s Disease), Dr. Goetsch was warning in a 1934 paper (S3), that iodine “has no place” in the treatment of autonomous nodules. “Non-toxic adenoma is commonly activated by indiscriminate treatment with iodine and the symptoms of toxic adenoma are exacerbated by its use.”

A 1977 study published in Clinical Endocrinology (S2) described how in “sixteen cases of toxic adenoma of the thyroid ... potassium iodide was given in doses of 100 micrograms a day for one week, 200 micrograms a day for another and 400 micrograms a day for a third week. There was a progressive increase in the serum T4 level.” The study concluded by warning “the physician should be aware of the possibility of precipitating or aggravating thyrotoxicosis in patients with an autonomous hot nodule by increasing their intake of iodine.”

A 1996 report on thyroid autonomy in the Journal of Endocrinology and Metabolism begins with the observation that introducing iodized salt into formerly iodine-deficient populations often triggers an outbreak of hyperthyroidism, and concludes that one of the main reasons is the prevalence of autonomous nodules in such populations. “Incremental iodine addition to the diet of patients with such adenomas induces hyperthyroidism.”

This 2003 review (S1) in the Annals of Endocrinology said, “In a patient with hyperfunctioning adenoma, iodine supplementation may precipitate thyrotoxicosis,” and pointed to a study of four subjects with hyperfunctioning adenomas with normal TSH who became “thyrotoxic when given 0.5 mg iodine [500 mcg] per day.” And, “in another study of similar patients, administration of only 0.1 or 0.2 mg [100 to 200 mcg] iodine resulted in substantial increases in serum T4 concentrations.”

More recently, a 2015 paper (S4) that while the recommended daily amount of iodine for health is 150 micrograms, the “Jod Basedow phenomenon can be seen with 300-400 micrograms of iodine.”

These amounts are definitely equal to the iodine in my heavy-handed use of salt (about 140 mcg per half teaspoon), added to the amount found in the three eggs (200 mcg) I ate most days. And it doesn’t even count the amount contained in the dairy products I ate near daily (65 mcg in a cup of cottage cheese) or the generous amount in the rainbow rolls and seaweed salad at the sushi restaurant I frequented (92 mcg in just one roll).

After reading these studies and others, I have no doubt that the addition of iodized salt to my already hefty daily intake of iodine caused my heretofore unknown hot nodule to ramp up its production of hormone to the point I went running to the Emergency Room with frightening heart palpitations and massive anxiety. (For this, I am ironically grateful, because otherwise I’d have never been diagnosed with the nodule and might have lived more years with mysterious and maddening symptoms that hugely impacted my quality of life.)

I don’t know why my endocrinologist didn’t acknowledge the possibility of a connection to the salt. He did, however, admit that “medical amounts” of iodine could cause an autonomous nodule to ramp up hormone production. When I asked him what he meant, he mentioned heart medications like amiodarone, which pack a big iodine punch. Too bad he didn’t mention contrast dye.

Only a few months later, after taking too much beta blocker to help get my still-jumpy heart rhythm under control, I fainted in a store and was again on my way to the emergency room. Having never fainted before, I had no idea that’s what it was, all I knew is a felt really really weird, to the point I worried I might be having a stroke. So what is the first thing the helpful ER staff wanted to do? Rule out a stroke with a CT scan that required iodinated contrast dye. After much dithering in my muddled head, I agreed to the iodinated dye. And each day over the next several months, I would really really wish I hadn’t.

Beware iodinated contrast dye with a hot nodule

It takes a good hour of internet searching to learn that small amounts of iodine in food or salt can cause a hot nodule to increase its production of thyroid hormone. But it only takes about 30 seconds to find literally dozens of studies that iodinated contrast dye can induce hyperthroidism in “at risk” individuals. The at-risk part is, of course, thyroid autonomy from a hot nodule that is more likely to lurk in those who are older, or who live in iodine-deficient regions.

There is simply too much iodine in contrast dye for someone with a hot nodule to handle. In this medical review, the authors explain that “A dose of contrast media used in typical radiological procedure contains about 13,500 micrograms of free iodide, and 15 to 60 g of bound iodine that can be liberated as free iodide in the body.” callout 6They call this “an acute load” vastly greater than the recommended daily intake of iodide of 150 mcg, or even than the “upper tolerable limit” of 1100 mcg of iodine established for those with a normal thyroid. Which might be another review, entitled Consequences of Excess Iodine, found that even people with normal thyroid function experienced “a 2 to 3-fold increased risk of developing either incident hyperthyroidism or overt hypothyroidism after exposure.” The review continues:

“After ICM administration, iodine stores remain elevated for up to 4–8 weeks ... In healthy US adults with intact thyroid and renal function, median urinary iodine concentrations increased by 300% from baseline to peak levels, and they did not return to baseline until a median of 43 days after ICM administration. In another study of patients in Brazil, urinary iodine levels did not normalize until 1 month after undergoing a single iodinated CT scan.”

However, as some authors point out, just because excess iodine is no longer showing up in urine doesn’t mean it is gone from the body. This paper states that after exposure to iodinated dye, “body stores of iodine in interstitial fluids, in colloid within the thyroid, and in virtually every organ in the body are expanded ... [which] substantially increases total body iodine stores for at least three months, and in some cases as long as 2 years (Costa 1978). A study by Spate (et al., 1998) measured iodine content in the toenails at monthly intervals following injection of iodinated contrast as part of a radiographic study done for medical purposes. They found that it took a minimum of 100 days (about 3 months) for the body iodine level to return to baseline following a single injection of iodinated contrast and the time required to achieve this in most patients in their study was 200–300 days (6-10 months). The study by Costa (et al., 1978) found that in some cases tissue levels of iodine remained high for as long as 2 years after administration of radiologic contrast material.”

Clearly that quick of rush of iodide into our veins does not go gently into that good night. It will hang around for a long awhile. And what is a hyperfunctioning nodule likely to do with all that excess iodine? - trap it and convert it into thyroid hormone, which it can store, and release, for months on end.

Hence, this paper (S5) describes how three months after an iodinated scan, a 62-year-old woman showed up at the Emergency room with heart palpitations. TSH was low, with elevated free and total T3 and T4…. After she was treated and normalized, says the study, “a nuclear radioiodine scan 6 months later demonstrated a solitary hyperfunctioning nodule.” No surprise there.

This study (S4) found that in 28 patients with hyperthyroidism at one geriatric hospital, 7 of them (25 percent), had been given iodinated contrast dye in the previous months, with the onset of hyperthyroidism showing up “3 to 8 weeks” after their scans. The paper concluded that “the frequency of this condition in a non-iodine-deficient area appears related to the more common occurrence of autonomous thyroid nodules in the elderly.” You don’t say?

Meanwhile, this paper (S3) relates how a 53-year-old woman presented with thyrotoxic symptoms and atrial fibrillation two months after a scan, which the authors found to be a late onset. “Although iodine-induced hyperthyroidism has been documented to occur 3 to 10 weeks after exposure to iodinated contrast, 75% of patients present within 1 month of exposure.”

I know that in my own case, it was exactly two weeks after being given iodinated contrast dye that I felt a return of hyperthyroid symptoms that had resolved just a month earlier after a 30-day course of low-dose methimazole (5 mg a day). My TSH had been holding steady at around an optimal 1.0 for weeks, even without medication, and suddenly it began dropping. I went back on methimazole, this time 10 mg a day, but my symptoms only intensified, and over a period of two weeks my TSH kept dropping until it reached an abnormally low .25. I felt miserable, heart-thumping anxious and shaky, and feared that my nodule would be hulked out on all that iodine indefinitely. I had to increase the medication to 20 mg a day – four times the amount that had worked before – to get my TSH to slowly start rising and get my symptoms marginally under control.

I learned firsthand how dangerous contrast dye can be for someone with a hot nodule. I shudder to think how that surge of hormones would have hit me if I knew nothing about the nodule, and didn’t have thyroid-blocking medication sitting in my medicine cabinet. I’m guessing I would have become full-blown toxic within that first month, and would have suffered even more severe symptoms. Yet here again, the medical profession seems to be oddly unaware of the problem. Before I was given the dye, I mentioned being diagnosed with a hot nodule, but the emergency room doctor told me I didn’t have anything to worry about as the iodine was not free but bound, and so couldn’t impact me. Obviously, not true. And even once my symptoms had kicked up again, my own primary care physician told me she didn’t think it could be because of the contrast dye.

I don’t know why more doctors aren’t knowledgeable about the risks of contrast scans to us nodule-sporting “at risk” individuals. Maybe it’s because thyroid autonomy is not very common here in the U.S. like it is in other iodine-deprived countries. Or maybe because even those who do have hot nodules are unaware of them, and don’t realize why they heartrate goes crazy and they feel so anxious in the weeks after their scan, and manage to muddle through until it goes away.

And luckily, it does go away. As the review mentioned above says, the production of excess thyroid hormone after an iodinated scan is “self-limiting” in nature, with an average resolution time of 116 days, or about four months. The iodine levels that fuel the surge eventually, thankfully, subside.

In my case, it was about seven weeks after my iodinated CT scan, after being on 20 mg of methimazole a day for a full month, before I felt a downshift in the “speedy” feeling that I have come to recognize as the leading edge of excess hormone symptoms. That was the point I was able to start tapering down the medication. But I didn’t return to my “before scan” state ...

Don't fuel a hot nodule: controlling iodine in the diet

I found it empowering to realize I could help stop the tide of excess thyroid hormone making me miserable by controlling the amount of iodine in my diet. Then I found out how difficult it is to figure out the amount of iodine in my diet, and so began long hours of frustrated searching.

Unlike just about every other nutrient necessary for health, the U.S. government does not test or track iodine in foods. Consequently, the few charts available on food iodine content list only about a dozen items, and that’s all there is to find. (I have provided it below). I can’t imagine who in the government made the decision to pass on adding iodine content to its list of vital nutrients to track, since both a lack of iodine or excess can cause such havoc in a population, but there it is. (See the Story of Iodine)

Even more frustrating is that with the foods known to contain substantial amounts of iodine here in the U.S. – eggs, dairy products and baked goods – there is no way to know exactly how much iodine any particular product might contain. Some dairies might use feed with iodine or iodinated disinfectant when milking dairy cows and some might not, and even in those that do, who can tell exactly how much iodine gets in the milk? callout 7Some egg producers might give their chickens iodine in their feed, some might not, and even those that do, there is rarely a label to tell you much iodine ends up in their egg yolks. Meanwhile, some bakeries might use potassium iodide to condition their bread dough, and some might not.

Then there are vegetables, some of which might have been grown in iodine rich soil and have a decent amount of iodine (a potato can have as much as 60 mcg), or they might have been grown in iodine poor soil, as in the infamous “goiter belt” states. How can we know when we are picking through produce?

Of course, until the 20th century, iodine was fairly scarce in just about every food except for seaweed and seafood, and iodine deficiency and its cruel outcomes was a real problem, hence the push to iodize the U.S salt supply in the 1920s. But today, iodine deficiency is uncommon in America. After all, the foods with the most iodine – eggs, dairy products, bread, and salt – are daily staples of our diet, and most of us get far more iodine than we need.

For example, a typical American breakfast of a three-egg omelet with cheese and a side of toast likely contains 250 mcg or more of iodine, and that’s before picking up that shaker of iodized salt. That’s far more than the recommended daily amount of 150 mcg in just one meal. Yes, more and more people are getting away from the “Standard American Diet,” some turning to a vegan diet that eschews eggs and dairy products, while others may choose to avoid things like bread and salt, and thus iodine. Ironically, these health-conscious decisions are one reason iodine status has declined in the U.S. since the 1970s. Still, even after the decline, the U.S. Food and Drug Administration reported in 2008 that Americans take in between 138 to 353 mcg of iodine per day, which is more than enough. And while the vast majority of people don’t have to worry about a mild excess of iodine – up to 1100 mcg a day is considered “safe” for most – those of us with a hot nodule can pay a big price for ingesting too much.

So exactly how much iodine is too much with a hot nodule? That, of course, is different for everyone, and probably depends on the size and activity of the nodule. Those with large, highly hyperfunctioning nodules might feel a bump in symptoms – and drop in TSH – from fairly small amounts of iodine above the RDA. A smaller nodule might not require such careful restriction to remain symptom free and keep TSH in the normal range. Some experimentation and tracking of foods might reveal what levels work best for you and your particular nodule.

Of course, that sounds more simple than it is. Besides the uncertainty in ferreting out the iodine content of specific foods, the whole enterprise is further complicated by the fact that a hot nodule can trap iodine from a food eaten today and use it to make hormone which it will then store and release weeks later. So in approaching iodine in your diet, it’s less about being rigid with a particular daily level, and more about developing long-term iodine-moderating habits.

Now, l know that the thyroid gland adapts to a certain level of iodine intake over time, and reacts badly to sudden changes in intake. So for me, I’ve drifted slowly down toward the RDA of 150 mcg; I want my thyroid to stay healthy and functioning as normally as possible. I also know that iodine deficiency is well-known to cause nodules to grow, and even precipitate the growth of new autonomous nodules, so it is very important not to go too low.

Thus, I try to shoot for the 150 to 200 mcg range, but I also try not to go too much higher than that, at least not knowingly. My experience with my own nodule – only about 1.5 cm in size according to my ultrasound – tells me that I will experience a return of racy symptoms if I consume more than 300-400 mcg a day over several weeks. This gives me room for flexibility, so I don’t worry about calculating the small amounts of iodine found in fruits, vegetables and meats, and basically just track the big four sources of iodine in food – eggs, dairy products, bread products and seafood.

Bread is easy, I just pass on it (who needs the processed carbs anyway?), and if I do want to indulge, at least there is an ingredient list that I can check to see if it is made with potassium iodide.

As for the rest, I no longer eat eggs every day, as one egg yolk is likely to contain between 50 and 70 mcg of iodine. If I do get a craving for eggs for breakfast, I now eat two instead of three, and I don’t add cheese to them. If I eat cheese or yogurt, I don’t go hog wild with it, and I don’t eat any other high iodine foods that day. If I know I am going to go out for sushi that evening, then I won’t eat any eggs or cheese that day. And I will order only one roll with seaweed in it, and rely on salmon sashimi (a low iodine fish) and vegetables and plain rice to fill me up. I also won’t order my former favorite appetizer – seaweed salad. (Sigh, oh how I miss it).

And of course, I will not ever, ever pick up a shaker of iodized salt again. I bring my own salt to restaurants, hidden in my purse, just in case.

Now, I have no way of knowing beyond my subjective feeling of lessening symptoms if my efforts to curb my iodine intake really make that big of a difference to my nodule’s hormone production. It would take a far more controlled experiment and regular lab testing to determine that for certain. But because I saw my TSH drop so precipitously after the addition of iodized salt to my diet – and because I can trace other symptomatic episodes in my past to experiments with kelp or iodine supplements – I feel I’m on firm ground in believing it does make a difference to keep iodine out of my mouth.

And after all, that feeling might be what matters most. As with any health issue in which one feels powerless over a bodily system gone haywire, managing the resulting emotions is often the biggest challenge. Anything you can do to feel empowered to help yourself, especially with a condition like that directly threatens mental health, is a vital effort for sanity.

Can you increase the elimination of iodine from the body?

After having a CT scan with iodinated dye and getting dragged into hyperthyroid territory again, I knew from reading different studies that I would have excess iodine in my system likely for several months, fueling my hot nodule, and wondered if it was possible to get it out of me any faster.

There is of course a very low iodine diet, outlined by the American Thyroid Association, which is usually recommended by endocrinologists to patients preparing for radioactive iodine treatment for cancers or intractable hyperthyroid disease. It aims for an iodine intake of under 50 mcg per day, and completely excludes the higher iodine foods mentioned above – eggs, dairy products, bread products and seafood. Such a low iodine intake wouldn’t help me eliminate the iodine already stored in my body, but at least in the short-term I figured it might help stop the storage of more, and maybe help me get to a euthyroid or normal thyroid state faster.

Then I found a web page that described how much iodine is lost in sweat. It presented study after study which showed that enough iodine can be lost in sweat – up to a 150 mcg per two-hour workout session for athletes in a high humidity environment – that many athletes in less iodine-rich countries develop goiter from iodine deficiency.

This was good news to me. And maybe helped explain why I always felt so much better during summers living in Phoenix, when I regularly hiked – and sweated profusely – on 90 degree mornings. Now I live on the cool California coast, and don’t have the sweat advantage here. And if I am in the midst of a thyroid hormone surge, with all its heart-flopping and muscle-weak symptoms, exercise becomes incredibly unappealing, not to mention more difficult. But I do have a sauna in my garage. If a good daily sweat can help keep get iodine out of my blood stream and away from my nodule, then maybe I won’t have to worry about that extra egg here and there.

Iodine content in food

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