Graves disease disrupts the thyroid feedback loop when autoantibodies bind TSH receptors and trigger excessive T3 and T4 production. This causes the characteristic lab pattern of low TSH with elevated thyroid hormones. The video walks through the normal hypothalamic-pituitary-thyroid axis and how Graves disease breaks it.
In this video, we're diving into the pathophysiology of hyperthyroidism, specifically Graves disease. And I'll give you the key critical thinking points that you'll need to know about it. So hopefully we can help all of this info come together for you and help you pass your nursing school exams. I also have a free quiz to give to you at the end, which is super fun, so let's dive in. So the first thing you need to know about hyperthyroidism and thyroid hormones in general is that they are part of what we call a feedback loop. Now, a feedback loop isn't as scary as it might sound right now. All that it means is that when the body needs something, the loop is triggered and the body gets what it needs. Then after the body is back to balance, it's gotten what it needed, that feedback loop stops. Think of it like a cycle or a circle. The body needs something, so the loop starts, and then the body gets what it needs, and a loop starts, stops. So here's a simple example. Hunger. So when you're hungry, your stomach tells your brain, hello up there, I need some food, please. And then that feedback loop is triggered. Your brain responds to that and it tells you to eat. Now, once you've eaten, your stomach then tells your brain, okay, cool, I'm good here. Thanks for the food. Now I'm all cool. Now I'm all good. And now that feedback loop slow circles back around and pauses until you're hungry again. See how that works? That's a feedback loop. So the same thing is happening here with the thyroid gland. And here's how this works. Let's walk through the physiology of this real quick so that you can understand the critical thinking behind it. All right? Behind hyperthyroidism or Graves disease, so there's a little part of the brain called the hypothalamus. His job is to release a hormone called the thyrotropin releasing hormone, or trh. That simple. Now, trh, it's going to travel down to the anterior pituitary gland and tell the anterior pituitary to release thyroid stimulating hormone, or tsh. Now, these are two different hormones, okay? Trh, thyroid releasing hormone, and tsh, thyroid stimulating hormone. I like to remember that the R comes before the S in the Alphabet and that the hormone needs to be released before it can stimulate. Stimulate something. Right? So those are the two good ways that I have found to remember it. I hope that that helps you, too. So now TSH is going to travel down to the thyroid gland and the Thyroid gland is going to release the active thyroid hormones. Now these are called triodothyronine, or T3, and thyroxine, which is T4. And these are the actual thyroid hormones that cause all the changes in the body. We'll get to those in just a second. Second. Alright, but TRH and TSH just help T4 and T3 to be released. But T4 and T3, those are the active thyroid hormones. And now once T4 and T3 are released and the body gets enough of them that it needs, it tells the hypothalamus and the anterior pituitary gland. I'm all good now, thank you very much. And then the hypothalamus stops releasing the TRH and the anterior pituitary stops releasing that tsh. That's the feedback loop. And here's a few normal ranges that you need to know for the NCLEX and your nursing exams. A normal TSH level is between 0.5 to 5.0 milli international units per liter. A normal total T4 level is between 5 and 12 micrograms per deciliter. And a normal T4 level is between 0.8 and 1.8 nanograms per deciliter. And the normal range for T3 is around 60 to 180 nanograms per deciliter. But these lab values can have some variation depending on your clinical site. So definitely be sure to check the reference ranges for your specific clinical site or wherever you're working. So how does this all relate to hyperthyroidism? Well, during hyperthyroidism, there is too much thyroid hormone in the body. And when I say thyroid hormone, I mean T4 and T3. Okay. Hyperthyroidism can be caused by any number of things, but the most common cause, and really the one, one of the biggest ones that you need to know about for nursing school, it's called Graves disease. So this is a big, big nclex disorder right here, my friend. You definitely need to know about this one. So please, please, please don't miss this. It's very, very important. During Graves disease, the body's immune system, it creates antibodies that attach to TSH receptors. So it's actually the body's own immune system that's attacking the thyroid. The immune system, it's isn't supposed to trigger the thyroid gland. Right? But in the case of Graves disease, that's exactly what's happening. The person's body is inappropriately making antibodies that go and trigger more and more thyroid hormone to be released. So let's put this into a simple step by step process. Walk through exactly what's happening here so that you can see really how this all fits together. Okay, so during hyperthyroidism, and in this case Graves disease, the body is making antibodies that trigger that tsh, the TSH receptors, and tell them to make more and more thyroid hormone, that T4 and T3. So this is step number one. There are antibodies that trigger those TSH receptors. So these antibodies are just like little proteins, and I like to think of them as little keys that unlock something. So when this antibody key is put into that TSH receptor, it stimulates that TSH receptor and that TSH tells the thyroid to make more thyroid hormone, the T4 and T3. That is step number two. The thyroid gland, now that it's stimulated, makes more and more thyroid hormone, that T4 and T3. Now there is more and more thyroid hormone, that T4 and T 3. Right. Roaming around the body. So now step number three, the hypothalamus and the anterior pituitary gland, they see that and they stop releasing TRH and TSH because there's already too much T4 and T3 in the body. Now here's a big critical thinking point for you here. Okay? What is this going to lead to? There's going to be more T4 and T3 in the body and less TRH and TSH. You see how that works? Because the thyroid gland is getting inappropriately triggered to make more and more thyroid hormone, that T4 and that T3. Right? And the brain sees that and says, well, I guess you don't need any more TRH or tsh, right? So it stops making it. So overall, there will be an increase in T4 and T3 in the body and a decrease in TRH and TSH. And that is now step number four. There's that increase in those thyroid hormones, T4 and T3, but a decrease in the thyroid releasing hormone and the thyroid stimulating hormone. That's a big key point for your nursing exams and the nclex because when you draw labs to check for hyperthyroidism, that TSH level will be low, but the T4 and T3 levels will be elevated. Now, I have a free quiz with practice problems for you to check your knowledge on all of this. Okay, this has been a huge request for our students, so I'm so, so, so, so excited to bring you more practice problems, my friend. So click on this video here and I'm going to walk you through some practice problems to really help this all come together so that you will be much, much more prepared for your exams. And of course, if you liked this video, be sure to show your support by subscribing to my channel. And as always, my friend, go become the nurse that God created only you to be. And I will see you over there in that next video.
