 When you have iodine deficiency and it's untreated for a long time, your neck can swell up and this problem is called goiter. But why? What has iodine got anything to do with your neck? Well, let's find out. We've already seen how your thyroid gland produces the two hormones T3 and T4. And if you look at their names, you can see that it's made up of three atoms of iodine triiodo and this is made up of four atoms of iodine. And so what happens if there's iodine deficiency in your body? Well, there will be deficiency of T3 and T4, there will be less of these hormones created. And because of that, the thyroid gland actually swells up and that's why your neck swells up giving you goiter. But why? Why does the thyroid gland swell up when it can't produce T3 and T4? Well, let's dig a little deeper. So imagine your body has iodine deficiency. What happens? Well, there is low levels of T3 and T4 and this is detected. The hypothalamus, which tells the pituitary gland, the master gland to do something about it. So the pituitary does something about the low hormone levels. It basically orders, orders, orders your thyroid gland to produce more of these. Now you may be wondering, well, how does it order? How does it communicate? We'll talk about that in a second. But at this point, it would have been nice if the thyroid could talk back and say, yes, I would love to, but there is no iodine in the body, there's nothing I can do about it. Unfortunately, no such communication exists. Therefore, what ends up happening is that it tells the thyroid to do this, the thyroid tries, but it doesn't, it can't manufacture T3 and T4 because there is not much iodine. And so then the pituitary detects that, hey, there's still low levels and continuously keeps ordering. It keeps on ordering the thyroid gland to keep on manufacturing T3 and T4. And because of this continuous ordering, the thyroid gland swells up. And this is where most of the explanation stops. But if you're like me, then this is not satisfactory, right? I mean, why is it that if you continuously ask or order the gland to keep on manufacturing T3 and T4, that it ends up swelling up? Like, what's exactly happening? For that, I dug a little deeper. I looked at the structure, exactly where these things are manufactured. What is the process? After going through all of that, I think, I think finally it all makes sense to me and I'm super, super excited to tell you what's happening. All right, so you ready? Okay. So bear with me. Let's quickly dig into the structure of the thyroid gland. So if you could look inside the thyroid gland, you will see stuff like this. There are a lot of things, but important parts for us are these circular looking things. These are given names. These are called the follicles. This is where the T3 and T4 is manufactured. But what exactly are they? Is that a cell? Like, are these cells? No, they're not. In fact, if you look closely, you can see the boundaries over here. There are dots. Those are the cells. And let me just zoom in to one of it. So I've zoomed in over here and you can see that the tiny dots are basically the dots over here. These are the cells of the follicles that are manufacturing T3 and T4. These are called follicular cells. Names are not important, but this is where the T3 and T4 are being manufactured. And then what about this stuff over here? Well, guess what? That contains all the raw material needed, raw material needed to manufacture T3 and T4. All right, now let's go back to our story. So T3 and T4 levels are down. The pituitary gland detects it. And remember we said we'll come back to this? Well, what it does really is that it secretes a hormone. This hormone is called the TSH. And you guess what it means? Well, it stands for thyroid stimulating hormone. I love such names because I know that this hormone is going to stimulate the thyroid gland. So it secretes the hormone into the bloodstream because in endocrine gland, it secretes into the bloodstream. And then this TSH, eventually, you know where it goes? It goes into the thyroid gland, but it actually goes and binds to the follicular cells. And when the TSH goes and binds to the follicular cells, the cells get activated to do two things. The first thing it does, and let's talk about a normal body first. The first thing it does is that it takes in the raw material that is needed to build this hormone and then it takes in the iodine from the blood and they react together to produce the required T3 and T4 hormones, which goes out of the follicle into the bloodstream. This is the first thing that it does. But there's another thing that TSH forces it to make. You know what? Well, the second thing is it has to replenish the raw material because if it didn't, then we will run out of the required raw material very quickly. So the second thing it does, it asks it to manufacture the raw material, the necessary raw material and push it back into that particular space. And so the raw material is replenished, everything is back to normal, the T3 and T4 are created, your body is working. But now imagine what happens when the iodine levels are low. Can you pause the video and try to connect all the dots and see what happens if you can now make sense of why the whole thing swells up? It has something to do with the second step. Okay, when there is no iodine, the first step doesn't happen because there is no iodine. There will be no chemical reactions taking place over here, no biochemical reactions taking place. So the raw material is not taken in, so it's not depleted. Yet the second step happens, the cells start manufacturing the raw material, anticipating that the first step would be happening, right? And because they're manufacturing and pushing into this, the follicles start swelling up. Does that make sense? It would have been nice if somehow, somehow this could have communicated the pituitary that, hey, you know what, there's a problem. Don't put, stop sending TSH because this is happening. But guess what? There is no way to send that communication. What ends up happening is that the pituitary continuously keeps sending TSH. As a result, the first step doesn't happen because there is no iodine, but the second step keeps on happening. The raw material that's inside that keeps on increasing, the pressure increases. As a result, the whole thing swells up. And as a result, eventually, if it's untreated, then depending upon how severe it is within a few weeks or within a few months, the whole thing swells up. And that's how you get quieter. So long story short, iodine is super-duper important in order to create these two thyroid hormones. So if you have low iodine, these hormones will not be created and you will have a lot of problems to begin with. But if your iodine deficiency problem is not solved, then when the TSH keeps stimulating the follicle cells, they keep on manufacturing more and more raw material, anticipating that iodine will come up, come in and, you know, react with it, but it doesn't. And as a result of that, the whole thing ends up swelling, causing goiter. This is the reason why we have iodized salts. That's why iodized salts is such a huge deal.