How to Control Your Metabolism by Thyroid & Growth Hormone

**Andrew Huberman** (0:00)
Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. This podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Four Sigmatic. Four Sigmatic is a wellness company that makes mushroom coffee. And if you're asking yourself, why would you want to put mushrooms in coffee? First of all, let me tell you, these are not psychedelic mushrooms, and no, the coffee doesn't taste like mushrooms. The coffee is delicious, and you don't taste mushrooms at all. I know this because I've been using Four Sigmatic coffee and been stocking it in my laboratory for several years now, long before I ever had the podcast, or Four Sigmatic was a sponsor. The two kinds of mushrooms that are in Four Sigmatic coffee are lion's mane and chaga mushrooms, both of which have been shown to have a slight anxiolytic effect to reduce anxiety. And lion's mane has also been shown in several studies to lower the symptoms of depression just slightly, although I wouldn't consider it a treatment for depression. That's an attractive benefit, as well as have some effect at offsetting cognitive decline. Albeit slightly, the effects were real in the studies that I found. So if you'd like to try Four Sigmatic, you can go to foursigmatic.com/huberman.
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MonkPak is a company that makes keto friendly snacks that taste incredible, but have just one gram of sugar or less. As I've said before on this podcast, I am not in ketosis. I'm not ketogenic. I don't advocate or follow any one particular diet. For me, what works is to fast in the early part of the day and to eat low carb and keto-ish throughout the day. That's for alertness and attention so I can work and focus and I don't feel sluggish or brain fog. And then at night and in the evening is when I tend to eat my carbohydrates to aid the transition to sleep. That's what works for me. Monk pack bars are a terrific snack, whether or not you're keto all the time, whether or not you're low carb or even if you're not. They are absolutely delicious. And I don't say that lightly. I'm not a big fan of bars in general. Most bars to me tastes like a combination of, you know, a metal bumper mixed with some cardboard and some lawn trimmings and some artificial sugar. Monk pack bars, when they were sent to me, I was like, all right, I'll try them. I tried it, like, uh-oh, this is a problem because I like them very, very much. And when I say it's a problem, it really is a problem. I actually keep the monk pack boxes in my basement so that I don't tear through them all at once. I'm a huge fan of the Caramel Sea Salt flavor. It's delicious. Just talking about it makes me hungry for one, but they also have sea salt, dark chocolate, peanut butter, dark chocolate. They're terrific. In addition to being keto friendly, they're also gluten-free, plant-based, non-GMO, no soy, trans fat, sugar alcohols or artificial colors. So all the bad stuff that you don't want. And as I mentioned before, they're keto less than one gram of sugar. If you want to try Monk Pak, you can go to monkpak.com. That's munkpak.com and enter the code Huberman at checkout and you'll get 20% off your first purchase of any Monk Pak product. That's munkpack.com and enter the code Huberman at checkout to get 20% off your purchase. This month we've been talking all about hormones, which are these absolutely incredible chemicals in our brain and body. They impact our entire lifespan. So from the time that we are in the womb, they are controlling the development of our brain and our bodies. After we are born, they are still controlling the development of our brain and bodies. And I did say development, and that's because contrary to what most people think, development lasts the entire lifespan. From the time you're conceived until the time you die, you are developing, you are changing, and hormones are constantly updating and changing the different functions of your body. They have two major kinds of effects. One are immediate effects, so they can actually bind to or kind of park in parking spots on cells and impact all sorts of things like the growth of cells, et cetera. They also can control gene expression. This is the way that hormones during puberty control body hair growth and breast development and growth of muscles and limbs and height and all sorts of things. They are incredible. We've talked about testosterone and estrogen. We talked about insulin and glucagon and some of the other things. Today, we are going to talk about metabolism, mainly going to talk about thyroid hormone and growth hormone and some other related pathways. I'm going to explain to you the logic of how thyroid hormone and growth hormone work. It will become obvious why I've paired thyroid and growth hormone together in the same episode. And I will of course talk about tools that you can use to elevate or reduce thyroid hormone. There are cases where people want to reduce thyroid hormone. I will talk about tools that you can use to elevate growth hormone. There are rare cases where people want to reduce growth hormone. Most people are interested in increasing growth hormone. So today is going to be rich with information, rich with actionable tools. And as always, the idea is to spell out an organizational logic so you can come away from this episode. And in fact, the entire month on hormones, really understanding at some level what these things we call hormones are and how they work. And that's really to arm you to encounter information going forward, whether or not it comes from me or from somebody else, a book or a course, someplace else online, to make sense of how to work with these incredible chemicals we call hormones. Before we begin to talk about thyroid and growth hormone and how our metabolism works and how to control metabolism, I want to answer a few questions that I received from you, from the audience. Every once in a while, someone will send me a quite earnest question about something they saw on the internet. And one of the things I've heard about quite a bit in the last couple of weeks is we've been talking about hormones and food intake and how those interact. Is this question of, are certain foods particularly good for certain organs of the body? And can that be predicted on the basis of the shape of those foods? So first of all, I want to acknowledge the question as a valid one because the, I see this every once in a while out there, people will say, well, you know, walnuts are in the shape of the brain and therefore they are good for your brain. Or, you know, a particular fruit like the beet often looks like a heart and it's good for your heart. And I certainly invite questions of all kinds provided they are sincere questions. However, I am not aware of any science whatsoever supporting the idea that the shape of a given food or object for that matter is relevant to its functional role in the body in reference to biology. Now, beets contain something that we're going to talk about today. They contain a substance called arginine, which actually can control the dilation of blood vessels and arteries. So it has some relationship to heart and heart health. Walnuts contain various fatty acids that may be, I want to underscore maybe, beneficial for certain aspects of brain health. But there's no evidence whatsoever that the shape of the food itself is relevant. And I think what's happened is that people have gone out there and found foods that contain certain substances like carrots and vitamin A or walnuts and particular fatty acids or beets and arginine. And they've selected the foods that happen to be in the shape of the thing, the organ that the particular substance like vitamin A or fatty acids and so forth might benefit or support. But of course there are many, many other sources of these nutrients that don't come from walnuts or from beets or from carrots. And so I guess the short way to put it is that the idea that the shape of some food is an indication of whether or not that food would be healthy for a particular organ in the body is absolutely unfounded. I don't know of any evidence for it. And I'm not out to quash anybody's great love of these foods. I enjoy all the foods I just described, but the shape of things in the physical universe bears very little, if any, relevance to the nutrients that it contains and therefore the organs that it supports. So thank you for your question. But if you see that out there, I would, I don't even think you need to tell the person who's putting that information out into the world. I would just, you know, back away slowly. One other thing before we move into today's material, last episode, I talked about the problems with emulsifiers in highly processed foods and the way that they can strip the mucosal lining of the gut and they can limit the signaling of hormones like CCK that can signal to the brain satiety, the signal to stop eating. And then we got into a discussion about artificial sweeteners. And I threw out Stevia as an artificial sweetener and several people reached out to correct me that Stevia is not an artificial sweetener. It is a non-caloric sweetener. And you are correct. I lumped artificial and non-caloric sweeteners together. And thanks to many of you that also sent me some references, it does not appear that Stevia can negatively impact the gut microbiome. It does seem unique among non-caloric sweeteners. There are probably others out there. The other thing that we discussed is how Stevia can lead to slight increases in blood glucose, but can also improve insulin management just slightly, probably cancels to zero in terms of its impact on blood glucose, provided it's not at concentrations that are super, super sweet. Ingestion of anything that's very sweet, whether or not it contains calories or not, artificial or not, will create an insulin response. In fact, just walking past a bakery and smelling delicious baked goods can increase your insulin secretion. And so I just want to point that out. Thank you for the information and the references that you found. Please send additional ones if you do find them. And I appreciate that you allow me to make corrections. Every once in a while, I misspeak here and the opportunity to make corrections keeps us all on the same page. And please do keep any feedback that you have about particular things I cover here coming my way. There is so much interest in metabolism. We hear about having a high or a low metabolism. There are some people out there who would like to reduce their metabolism. They simply can't eat enough to maintain their weight. Most people, however, struggle with the opposite issue. They struggle to maintain a healthy weight and or their metabolism is too low. Now there are a variety of reasons why metabolism can be low. Today we are going to talk about two hormones, thyroid hormone and its related pathways and growth hormone and its related pathways, which arguably are the two hormones and two systems in the body that are most significant for setting your overall level of metabolism. Before we dive into those, I just want to cover a little bit of what metabolism is. And I want to talk about which organs in your body use the most energy. So metabolism is the consumption of energy, not necessarily eating, but it's the use of energy in the cells of the body for growth of tissues, for repair of tissues, and also just for day-to-day maintenance of function. A good example of maintenance of function would be your brain. Most of your metabolic needs, your so-called basal or resting metabolic needs are for your brain, for thinking. If you were to just sit in a bed all day and do nothing but think, that consumes about 75% of your metabolic needs. Now, there's also moving around. If you have a job that requires a lot of heavy labor or lifting things or you're a new parent and you're carrying kids around and you're going up and down the stairs or back and forth to the refrigerator for formula, et cetera. Well, then you're burning more energy, burning more calories. But even if you are very physically active, unless you're an ultramarathoner or a marathoner, chances are that 75% of your metabolic needs are coming just from your brain. And that's because neurons consume a lot of energy. Neurons, of course, are just the nerve cells of your brain. So these two hormones, thyroid hormone and growth hormone, we think of as related to metabolism of things in the body, keeping body fat low and keeping muscles strong and tendons strong and repairing themselves, et cetera. But they are also key for brain function, for the ability to maintain cognitive function throughout the lifespan. So the big theme I'd like to introduce is that metabolism isn't just about losing weight, but having a high metabolism, provided it's not too high, is great. It means that you will have more lean tissue, more bone and muscle and less adipose tissue fat. And we know that that's healthy. How much fat and how much muscle? Well, that varies and the numbers on this are always shifting. But in general, muscle and its related tissues burns more energy than does adipose tissue or fat. And the water in your body doesn't consume any energy. So metabolism can be increased simply by adding muscle to your body and reducing fat or adjusting the ratio of the two. But regardless, even if you're not interested in changing body composition, these two hormones, thyroid hormone and growth hormone are super important for metabolism of all kinds, including tissue repair after injury, including maintaining cognitive function and well-being and the ability to think clearly as you age, offsetting dementia and so forth. So the big theme here really includes the previous episodes. You don't have to have seen those episodes, but for the last three episodes and today as well, we've been talking about hormones, these substances that are released from one location in the body that go and act other locations in the body. I'm going to tell you how that works for thyroid and growth hormone. But now that you've heard about testosterone and estrogen, and you're going to hear about thyroid and growth hormone, I want you to realize that there's a repeating logic. First of all, there are neurons in your brain in an area called the hypothalamus, which just means it's below the thalamus, hypo. It sits at the base of your brain in the front, it's part of the forebrain. So it's more or less above the roof of your mouth, maybe about a centimeter or so, and then about a centimeter forward, in most people. And neurons in the hypothalamus release hormones that are called releasing hormones. So we've talked in previous episodes about, for instance, gonadotropin releasing hormone. So those are little neurons that then signal another brain area called the pituitary to release other hormones. Today, we're going to see this again. In the brain, you have neurons that release thyrotropin or thyroid releasing hormone. You also have growth hormone releasing hormone. So anytime you hear releasing, chances are those are neurons that are in your brain and they extend little wires, we call axons, into your pituitary. And the pituitary releases a bunch of hormones into the bloodstream. And the pituitary releases things that most often have the name of stimulating hormone because they stimulate organs. So in keeping with the theme of thyroid hormone, you have thyroid releasing hormone in the brain, tells the pituitary to release thyroid stimulating hormone. And then the thyroid, which we'll talk about in a moment, releases thyroid hormones. In the testosterone and estrogen episode, we talked about how you have gonadotropin releasing hormone. There's the releasing again up in the brain. Remember releasing hormone comes from the brain. Then you had things like luteinizing hormone and follicle stimulating hormone, which were in the pituitary and those traveled to the ovaries or the testes and acted on those tissues. Okay, so please try and embed this logic. If you hear the word releasing hormone, it's coming from the brain. And that makes it actionable in certain ways that we'll return to later. In addition, the pituitary is letting go of all these hormones into the bloodstream that are stimulating different tissues. So for thyroid, it's thyroid stimulating hormone, and then it goes to the thyroid. And the thyroid is a little butterfly shaped gland that's right around the Adam's apple. If you want to see yours, not directly, because it's got skin over it, what you would do is you'd take a sip of water, you'd look in the mirror and you'd swallow. And the thing that moves up and down, that is your thyroid. Now, some people call it your Adam's apple because it sits right near this protrusion in the trachea, which is the Adam's apple. No matter whether or not you're male, female, or regardless of what your chromosomal background is, everyone has an Adam's apple. It tends to be more pronounced in people. They got a surge of testosterone early in development because it has a testosterone sensitivity to it. And that actually controls the timbre, the so-called deepness of the voice. So the thyroid gland sits right there and it's got four little bumps behind it called the parathyroid gland. And it releases two hormones into the blood to stimulate different tissues and their metabolism. And those hormones are called T4 and T3. So if this is already sounding like a lot of information, it's really easy. I promise. Releasing hormone comes from the brain, stimulating hormone comes from the pituitary. And in this case, we're talking about the thyroid binding up that stimulating hormone and saying, oh, I need to release something that releases T4 and T3. And guess what? You can basically forget about T4. T4, it's not completely inactive. It has some roles, but T3 is the one that's more or less active. Now, what does thyroid hormone do? A lot of people think, oh, thyroid, it's like metabolism. And people who are hypothyroid will have bulging eyes and are real thin. And people who have hypothyroid are overweight. And they have like, their eyes are like, are, you know, half closed or something. And indeed, thyroid hormone controls a lot of the features of the face and the eyes, and it can control amounts of adipose tissue and so forth. But the main role of thyroid hormone of T3 is to promote metabolism. And that doesn't just mean the consumption of energy. It means the utilization of energy, including the buildup of tissues. So it acts on all sorts of target tissues in the body. It acts on muscle. It acts on the liver. It acts on the cartilage. It acts on the bone. And it's not just involved in using energy. It's also converting energy. I do realize I said that twice. It's involved in taking fats and breaking them down into fatty acids and converting those into ATP, which is an important thing for cells to use energy. It's also involved in taking sugars and turning those into energy. And yes, it goes to adipose tissue to fat. We have different kinds of fat that we'll talk about today, but it goes to white fat and it liberates or helps liberate some of the fats from those fat cells and use them for energy. And this is why higher thyroid is associated with leaner bodies, lower thyroid is associated with less lean bodies. So one thing that's absolutely key and is actionable, we're right there already in discussing tools is iodine. Iodine comes from things in the ocean, right? And here are a couple of interesting facts about iodine. And then we'll talk about whether or not you should be supplementing iodine or not. First of all, iodine is most common in sea salt, in kelp and in seaweed. And most people can get enough iodine from the food they eat and or the table salt they consume. Almost all table salt from all over the world, regardless of where you are, contains iodine. The thyroid needs iodine in order to produce thyroid hormone and you need sufficient levels of thyroid hormone. Not too much, but you need it. So chances are you are getting enough iodine, although you might not, especially those of you following a particularly quote unquote clean diet might not be getting enough iodine. Here's the deal with iodine. Iodine combines with an amino acid that we've talked about before called L-tyrosine. L-tyrosine comes from meat, from nuts. There are some plant-based sources as well. It is the precursor to dopamine. But in the thyroid, iodine combines or works with L-tyrosine to produce T3 and T4, the thyroid hormone. So you absolutely need sufficient iodine. You need sufficient L-tyrosine. And then you also need something else, which is called selenium. And we'll talk about selenium in a moment. So there's a condition that shows up in little pockets in the world. It's not super common, meaning it's not very widespread, but in certain areas that are far away from the ocean, at one point, this was historically in the Midwestern states of the United States, in some mountain regions of other countries, in some areas of Africa that were far from the ocean, people would get extremely swollen bulges in their necks. And this was called goiter. And the reason they were getting those swollen bulges is because the thyroid itself was hypertrophying. It was growing in an attempt to churn out more thyroid, and because it was getting a lot of stimulating hormone from the pituitary. But, and I don't want to go too far off track here, but as you recall, the brain and the pituitary are paying attention in a cellular sense to the levels of hormones in the blood. And when those hormones get too high, they shut off the stimulating hormone. They shut down the signal to make more, kind of like a thermostat. When the levels are too low, like there's not enough testosterone in the bloodstream or there's not enough estrogen, the brain will continue to push out the signal to make more. Similarly, if there's not enough thyroid circulating or there's not enough iodine to make thyroid, therefore not enough thyroid hormone circulating, the thyroid gland itself is not getting shut down. There's tons of stimulating hormone and releasing hormone coming from the brain, like release, release, release. And there's no way they can make thyroid hormone instead the gland just gets bigger and bigger and bigger. And so people get goiter. This is one of the reasons why table salt has iodine in it. Although there are other foods that have iodine in it as well. So how much iodine do you need? Well, you don't need a whole lot. Some people who are hypothyroidal, might, and I want to emphasize might, you absolutely should talk to your doctor. This is a serious matter. Anytime you're talking about hormones or manipulating levels of thyroid, you absolutely won't talk to your doctor. Some people benefit from supplementing iodine. It is contained in most salts. It's in Himalayan salt, not always, but often. I know these days there's a lot of excitement about pink salts and sea salts, and the kind of artisan salt thing has kind of taken off in the foodie land, which is great. Some of them are actually quite tasty. You can just take it directly if you like the taste of salt. But iodine can be supplemented through things like kelp and seaweed and kelp tablets. Now, if you are hyperthyroidal, you make too much thyroid, that actually can be a problem. So really the best way to figure this out is to get your blood levels tested of thyroid hormone. But there's so much iodine in the ocean that believe it or not, people that live near the coast can actually just absorb it through the air just by breathing ocean air. So that gives you a sense of just how little iodine you actually need to consume in food or in salt. So if you're within a few miles of the ocean or you visit the ocean from time to time, you're probably getting plenty. It does have to come together, as I mentioned, with L-tyrosine. And this is why foods that contain L-tyrosine and provided that you have sufficient iodine in your diet and if you have sufficient selenium in your diet does serve to increase your metabolism. And that is again, is for the growth and repair of tissues. And that's really important. It's not just about keeping your metabolism high so that you can be on the leaner side of things or just your body weight, excuse me, your body composition ratio is the way you like. repair of injuries, repair of brain tissue, clearance of any damage from neurons, clearance of any damage to the body is also going to depend on thyroid. again, metabolism being this kind of rate of fuel consumption and use in the body generally, not just about body mass indexes and things of that sort. So let's talk about selenium because it's really important. And even though most people are getting a lot of sufficient iodine and most people are probably getting enough l-tyrosine, I'm guessing most people may not be getting enough selenium if their goal is to increase thyroid hormone. At least that's what the literature says. Without going into the biochemistry, selenium is important in order for thyroid hormone to be made because of the way that it allows l-tyrosine and iodine to interact. And the thing is, most people aren't getting enough selenium because they don't eat foods that are high in selenium. Now how much selenium you need will depend on where you live. It actually varies country by country. Some countries I found say that you should get 100 micrograms, some say 200, some say 155 The average was about 155 micrograms, the countries I looked at. People who are trying to increase thyroid levels might want to consume more selenium. And if you consume a vitamin, of course, you want to make sure if it has selenium, that you're not overdoing it by consuming a lot of selenium rich foods either. But nonetheless, I think it's fair to say that most people probably could do well by ingesting slightly more selenium than they currently are. Although of course, always talk to your doctor. Brazil nuts are the heavyweight champion of foods to get selenium from. It has very high concentrations of selenium. In just six or eight, Brazil nuts contain something like 550 micrograms of selenium. It's also present in fish. So certain fish like yellowfin tuna. Although nowadays, whenever I mention tuna or shellfish, which is the other rich source of selenium, people will tell me immediately, there are all sorts of issues around farm, not farm, mercury, et cetera. So I've never particularly liked eating fish because of the way it tastes. So that's why I avoid it. But for those of you that like it, I'm sure you're much more skilled in knowing which fish to buy and which fish not to buy. Ham, of all things, contains a lot of selenium for whatever reason pork does. I'm not a big consumer of pork. Beef has some selenium. But what's interesting, if you look at the sources, pork, beef, turkey, chicken, cottage cheese, eggs, brown rice, what you want to understand is that Brazil nuts, six to eight Brazil nuts has 550 micrograms of selenium and all the other foods I mentioned at much greater portion size than equivalent to six to eight Brazil nuts, either by volume or by calories, they have something like 30 to 50 micrograms of selenium. So if you're not eating Brazil nuts, and I'm guessing most people aren't, and you're not eating a lot of animal-based foods, which I know many of you aren't, then you're probably not getting enough selenium. And again, you can have these levels measured, or you can just check what you're consuming and figure out whether or not you're meeting the ration that you need in order to get healthy levels of thyroid. It is present in things like mushrooms, but again, in a bowl of mushrooms, what is the equivalent to a bowl of mushrooms? 12 micrograms of selenium. And if the daily ration is something in the 100 to 200 range, again, look it up for the area you are, you can see really quickly why. Even though things like mushrooms and spinach and milk and yogurt and lentils and cashews, and now we're into the vegetarian segment in the list that I constructed, you're probably not getting enough selenium. So it's kind of an interesting thing. If you're an experimenter and you get the clearance from your doctor, you could try increasing your selenium levels and see how that impacts your metabolism. again, Brazil nuts are probably going to be the most direct way to get sufficient selenium levels, but because levels are so high in Brazil nuts, it also means that you could overdo it as well. I'm not really aware of what the consequences are of getting too much selenium, although you can get too much of anything, and I'm guessing those consequences aren't good. I also want to mention that for children, their daily requirements of selenium are much lower, as low as 30 or 40 micrograms for kids 14 years or younger. And in some areas, I really want to underscore this, the amount of selenium that's recommended daily is as low as 55 micrograms. So it's not that you should be shooting for thousands or even high levels of hundreds of micrograms of selenium. And again, that's micrograms, not milligrams. So again, look into what you need. But if you're somebody who's interested in keeping thyroid function healthy and productive, then you certainly want to make sure you're getting enough iodine, you're getting enough selenium, and you're getting enough l-tyrosine. And it's interesting when you start looking at the various foods, especially highly processed foods, then you start to realize that perhaps many people, maybe you, are not. Not incidentally, selenium has some other effects on health that can be quite positive. And even though these don't relate to thyroid or growth hormone function specifically, I think you might want to know about them given that we're on the topic of selenium. The first is that there are three studies, all of which showed very high efficacy for reducing the risk of something called preeclampsia. Excuse me, preeclampsia. Preeclampsia is seizures that are related to blood pressure issues during or around the delivery of a new baby. And it actually, it's a rare-ish condition, but it actually can be quite deadly. And so the fact that selenium is important for offsetting preeclampsia risk is interesting. I don't know the exact mechanism, and I'm guessing there are only a few of you out there that are either pregnant or thinking of conceiving soon, but that's worth noting, obviously, anything related to pregnancy or lactation, especially talk to your doctor. I'm guessing that selenium is probably in a lot of prenatal formulas, but that's one clear benefit of having sufficient selenium. The other is a reduced prostate cancer risk. There's a study showing that having sufficient selenium can reduce prostate cancer risk. And there is some evidence that if you consume foods from areas with soil that's low in selenium, that can be a problem. And last episode, we talked about all these issues related to soil quality, things that are making their way into food, they're disrupting hormones and so forth. But having sufficient selenium from food could offset the low content in any soil. And so that apparently can reduce prostate cancer risk. It's a minor effect, but it's a statistically significant one. And the other one is a reduction in acne, which is interesting, I'm guessing that that probably has to do with the thyroid hormone pathway because of the way thyroid hormone can impact the liver. And it turns out that the liver and various biochemical reactions in the liver can impact acne. And that's probably an episode all into itself, but those are just some additional benefits of getting sufficient selenium. Okay, so we're already deep into tools related to making sure that you have sufficient selenium, iodine and L-tyrosine in order to make enough thyroid hormones that can support your metabolic processes in your liver, your muscles, your tendons, for whatever purpose, keeping your metabolism high for body composition reasons or for healing, for keeping your brain working well. Earlier I mentioned there are people who are following very clean diets. So these are people that consume no processed foods. Any starch they might eat is going to be maybe a rice or a grain or any protein they might consume is going to be either from, let's hope from humanely raised animal sources or maybe they're pure plant-based. Believe it or not, those folks are actually very susceptible to low iodine because it turns out that diets that are very meat rich and don't have many vegetables as well as diets that are very vegetable rich but don't have many meats or salts are at risk of lowering thyroid hormone by way of the iodine pathway and other pathways. And so let me try and simplify this for you.