 Alright, let's talk about how we actually produce the thyroid hormone. So first of all, the thyroid hormone is produced, it's built in the colloid, but the follicle cells themselves have an important job and their first job, we're going to see if we can get this to work, is to produce a substance called fibroglobulin. So fibroglobulin is produced inside the cells. And basically what I'm going to draw you a picture of it, because essentially fibroglobulin is the amino acid tyrosine, I don't know if you remember that thyroid hormone is an amino acid derivative, and essentially its fibroglobulin is 70 tyrosine molecules and tyrosine is just an amino acid in sequence. Do you think I'm going to draw 70 of them? Are you afraid? I'll stop. Once thyroid globulin is produced in the follicle cell, it's exocytosed out into the colloid. So that works, like now we have it in the colloid. Now, the second thing that happens in the follicle cell is that iodine, iodine is transported into the colloid. And so here's the scoop. Here is a little transporter. I'm going to do this in another cell. I'll do this one up here. There's an iodine transporter that transports, I don't know if you remember all my color coding, sodium and iodine into the follicle cell. And that's a simporter. And so they're working together, but the sodium is pumped down its concentration gradient and it allows iodine to come along with it. Now on the luminal edge, I had to think about that for a second because this would be the luminal edge of the follicle cell. There's another guy that transports iodine in and this guy's name is Pendrin. And I'm telling you this because I think there's clinical significance to a malfunctioning Pendrin because you can't get your iodine into the colloid. Okay, so once iodine is in and thyroglobulin is in, the iodines are added to the thyroglobulins. So remember that each box was just a tyrosine amino acid. So basically they get iodated. I don't even know if that's a word. Iodized, that's what they get. And they get iodized with either one or two and iodines added to them. Now here's the scoop and I want you to visualize this for a second. The fact is that this thyroglobulin is really, it's really long and it makes this kind of messy tangle. Okay, and I'm going to try to make it do what I want to do because the next thing that happens after the thyroglobulin gets iodated, I mean iodized, then watch. A place that has one iodine forms a bond with a place that has two iodines. And look, whoa, bad. I hate it when it does that. It makes those random circles. It forms a bond like right here. Now, do you see that? So watch, I'm going to make a little circle around this so that you can see this right here. That is one flavor of thyroid hormone. It's T3, thyroid hormone. Ultimately, a tour combined with a oneer and made a threeer. You can also have a four, T4. And T4 happens, let's see if I can make one. There's a tour and here's a tour. And then they combine with each other. Did you follow that? And now we have another thyroid hormone. That's T4. I just showed you that because I had a really hard time visualizing how the thyroglobulin pieces that had two iodines connected to the ones that had one iodine to make T3 and T4. T3 and T4 are your thyroid hormones. So watch. After you iodate, iodize the thyroglobulin, then you fold and combine your threes in your ones, your twos in your ones, the equal threes in fours. And then you, I've got to put it down here, endocytose, that says endocytose. Are you going to endocytose, my friends? How about let's just take this whole folded thyroglobulin thing and endocytose it into the follicle cell. Once it's in the follicle cell, part six, you have an enzyme that slices it up. So you had thyroglobulin in the follicle cell, endocytose it, add iodines, fold, endocytose the whole thing in the follicle cell, and then chop it up. Chop up the hormones. And you get T3 and T4. T3 and T4. And again, you're chopping all of these things up, and then you exocytose the T3 and T4 into the bloodstream. Does that work for you? You can store, oh gosh, I read it somewhere, how much you could store like weeks worth of thyroid hormone in a single follicle, in the colloid. So you basically only endocytose this step and you need thyroid hormone. Otherwise, just leave it in the colloid and save it for later. All right, let's talk about what thyroid hormone does.