 Let's start out looking at the thyroid hormone or the thyroid gland or the set of hormones that are involved with thyroid. And we've got two of them that we're looking at in detail. Two of them, you know, our scenario in this lab is that these students actually were adding hormones to lab rats and then they misplaced the labels or something and so they don't know what hormone got added to which lab rat. And your job is to look at the lab rats and figure out what hormones were added. When we're dealing with the thyroid related hormones, we actually are only looking at, our students only added two of them. So we only have thyroid releasing hormone that is naturally produced by the hypothalamus and stimulates the release of thyroid and stimulating hormone from the anterior pituitary, which acts on the thyroid gland which produces thyroid hormone. Really? This is very, this pathway is very common. So we have the hypothalamus telling anterior pituitary to do something and Pitt sends out the message to the effector organ saying, make us some hormone. The hormone gets produced and then the hormone goes out and causes an effect in your body. One of the things that thyroid hormone does is it basically increases metabolism and if you end up with too much thyroid hormone, your metabolic rate is too high and you actually get kind of skinny and your eyes pop out and you're hot all the time because you're burning lots of fuel. If thyroid hormone is too low, then everything slows down. You get cold, you put on weight, you get tired and lethargic because thyroid hormone directly impacts your metabolic rate. So your job in this whole thing is to look at this chart and we're going to say, okay, what if we dumped in a ton of thyroid releasing hormone? That is one of the hormones that these students treated the rats with. So you dump in all this thyroid releasing hormone and the question is, if we poured in tons of it, what's that going to do to the pituitary gland? Now look up here and you can see that, now this is where normally your hypothalamus, when it produces thyroid releasing hormone to the amp pit, which produces thyroid stimulating hormone to the thyroid gland, which produces thyroid hormone, the reduction of thyroid hormone actually feeds back negatively to everything else and says, whoa, we've got plenty. So the more thyroid hormone you have, you're going to have a little negative feedback loop that says, okay, we've got tons. Thyroid gland, no need to make more. The thyroid hormone also feeds back negatively to amp pit, saying plenty, no need to produce any more of that stuff. It even feeds back negatively to the hypothalamus. Saying, no worries, we've got tons of this stuff. You don't need to be producing TRH anymore. Amp pit, no need to produce TSH. Thyroid gland, no need to produce any more thyroid hormone. That's a negative feedback loop. Does that work for you? Now think. Think, engage those fantastically brilliant brains of yours. All of a sudden, I say, hypothalamus, I'm taking over your job and I'm dumping in TRH, like mad TRH, go ahead, let's just see what happens. So I am going to just pour in massive quantity, like way more than your body would ever produce and completely ignoring any messages to the hypothalamus saying don't produce any more. I don't care, I've got tons of it. What's the message? What is the outcome going to be on amp pit? If there's lots of thyroid stimulating hormone, amp pit is going to be more active. Do you agree with that? And so you, this is like, I'm saying, I'm increasing the activity of amp pit and watch. Over here, I'm going to say, you know what? I'm going to expect that amp pit has been ordered to get more active and produce more stuff because that's what thyroid releasing hormone does. If there's tons of it, then amp pit is getting a message, dude, I got to make more. Amp pit is going to grow and amp pit is going to make more because thyroid releasing hormone is telling it to. Amp pit is making more, making more of what? Thyroid stimulating hormone. So not only do we have more releasing hormone, because of all that releasing hormone, we're going to have more thyroid stimulating hormone. And what's the impact of having more thyroid stimulating hormone? Dude, you are going to end up, really, we better rock that thyroid gland. It's going to get huge, right? Because we're sending the message saying, we don't have enough, we don't have enough. Thyroid gland, we would also expect to increase in size. Does that work for you? Do you see the adrenal gland anywhere in here? Do you see the thymus gland mentioned? The testes, the prostate, the seminal vesicles, what about body weight? If we have massive amounts of, you know, our thyroid gland is increased, we're actually probably going to produce lots more thyroid hormone. What's that going to do to your body weight? What did I say? Too much thyroid hormone is going to cause your body weight to go down. These are the characteristics that we're going to expect to see in our rat if the hormone is thyroid releasing hormone. Does that work for you? All right, let's see if it works for you. The next one is thyroid stimulating hormone. Now you're going to have to take a deep breath and ignore all these other marks that I've made. Now I am ignoring ant pit. I'm ignoring the hypothalamus and I'm just saying, dude, I am making mad, mad thyroid stimulating hormone, which is going to make mad, mad thyroid gland. Do you agree with that so far? So what's going to happen to the size of your thyroid gland, would you think? Thyroid stimulating hormone is going to increase my thyroid gland and I'm adding that without any input, without any feedback. But now my thyroid gland got big, so I've produced lots and lots of thyroid hormone. And what does it do? What does thyroid hormone do to the hypothalamus? It says, whoa, man, whoa, whoa back. We do not need any more releasing hormone. We've got tons. In the first scenario, we just added releasing hormone. We didn't care that the hypothalamus was saying no need for more. This time, we haven't added releasing hormone. And so the amount of releasing hormone is going to go down because your body is going to be like, what the hell, I've got thyroid hormone coming out of my pores. Like what, why do I have so much thyroid hormone? The hypothalamus is going to be like, I'm not producing any more TRH. Which, how's that going to affect? How's that going to affect the pituitary gland? There's nothing telling the pituitary gland to increase in size. In fact, the pituitary gland probably will decrease in size. Will any of this other stuff be affected? No. Will the body weight be affected? Yeah, it's going to decrease. And why is it going to decrease? Because of that same reason. We've got tons of thyroid hormone. The difference between these two, and this is really cool. Because now you kind of have a sense, oh, I know what I'm going to look for in my rats. I'm going to look, if my rat was treated by TRH, then its pituitary gland is going to be bigger than the control rat. The thyroid gland is going to be bigger than the control rat, and the body weight is going to have decreased. If that's almost all true. If that's almost all true. But the pituitary gland did not increase in size. Maybe it even decreased in size. Then, do you agree, then it's thyroid-stimulating hormone instead. Do you see how you're going to use the information from this chart to figure out what hormone treated what rat? And this is basically your hypothesis. This chart is essentially saying, what I think is going to happen, and then you're going to look at your rats and speculate on whether that was true or not. I'm just going to put little negative marks in here and indicate there's not going to be an effect. We wouldn't expect to see an effect on those other organs. The cool thing is that during this lab I'm actually going to give you a bunch of dead rats. These are my rats. Can you see that? Whoa, so cool. So the rats, you can see that they actually have all these organs. They're the testes. And you are going to... The weights of the organs are right here. I have the handout. I don't know why I didn't just show you the handout. Oh, yeah, because it doesn't have the dead rats on it. That's because the dead rats are for you to figure out. In lab, of course. You look at your dead rat and you're going to find the one that matches this scenario. Do you love me? I love you. Let's talk about the adrenal glands and what we would expect to see there.