 The first kind of hormone we're going to look at is the steroid hormone. Now, steroid hormones usually end in the word sterone, like testosterone, or progesterone, or aldosterone, or cortisol. But you'll remember cortisol is also a steroid hormone just because, check this thing out, they all kind of look very similar just because they're all made from cholesterol. If you remember, cholesterol is a lipid, and as such, it's hydrophobic. So you can imagine, it's like, if you barf steroid hormone into your blood, you're actually going to be putting something oily or fatty into your blood. And that, so it's this hydrophobic substance. That actually is going to affect its mechanism of action. So let's go make a list of characteristics about the steroid hormones that are significant to us. First of all, just like any hormone, they get dumped into the blood. That's the first thing that happens. So there's my little bloodstream, and here's my little steroid hormone. Okay? Now, the anatomical structures that produce steroid hormones, usually they're made in the gonads, which in females, ovaries and in the fellas, the testes, and they're also made in the adrenal glands. So this is the anatomical place where they come from. Who are they going to affect? That depends on who has receptors for the specific hormones. So the next question is, how do they act? How do they carry out an action? And what are some key characteristics of the actions that they produce? First of all, because they are in the blood and yet they're a hydrophobic, they don't like water. Basically, blood is water. So they're sitting inside this bloody water going, this is not cool, and they'll all clump together like oil and water unless they are being carried. They have their own little special carrier boats. I'll even make a little flag there so that you remember that this is a little boat. It's probably made out of a protein which is hydrophilic and so then it can float through the water but it needs, or it can float through the blood, but it needs that carrier in order to be able to do its job. Now, we will have some kind of target cell and here's the interesting thing. I'm going to tell you, of course, you should assume that how is the steroid hormone going to have an effect? It has to come in contact with the receptor. That's the first thing. So if you have an organ that does not have testosterone receptors, then that organ, it doesn't matter how much testosterone is in your system, that organ will not be affected because it doesn't have the receptors for it anyway. But steroid hormones are unique. Most of the time, the receptor is not embedded in the cell membrane like you would expect. What am I drawing right here? Most of the time, the receptor is floating in the nucleus and this is a hint to its action, like what it's going to actually do. Now, think about this. Steroid hormones are hydrophobic so they can easily pass through diffuse through cell membranes and look, in they go. And look through the cell membrane and that's the nuclear envelope. And look, they find these floating cytoplasmic or nuclear receptors. So this is a receptor that's just chilling. It's floating in the nucleus. They can float in the cytoplasm. Sometimes steroid hormones do have receptors that are embedded in the cell membrane. I'm going to put them in all the locations. But most of the time, they're actually found inside the nucleus. This is where they are most of the time. Because they're hydrophilic, I mean phobic, because they're hydrophobic, the steroid hormone just diffuses right in. Now, the action, that's how the hormone gets in. The action happens when the hormone binds to the receptor. So that's stage one. It's in the nucleus. So go ahead and take a wild guess. Like, what do you think is going to happen? Well, what we're actually going to produce, step two, is going to be to produce some kind of what? Some kind of machinery. Does that work for you? Some kind of necessary stuff to increase protein synthesis. What does that make you think of? Well, the whole purpose of DNA is to contain the directions for building proteins. Hopefully, you're getting a sense that these proteins that we're building are actually super important. If we're going to increase protein synthesis, it isn't just like, okay, go, make some proteins. It's like, we need this specific protein. And that's what this receptor plus this hormone stimulates. If protein synthesis increases, and you end up with some sort of product, some sort of protein, what is it? An enzyme? Is it another substance that's going to get dumped out somewhere? Does it have a specific effect on the heart? Does it have a specific effect on the size of the gonads? Who knows what the actual product is going to do, but the product causes the action or the impact. And here's the deal. Steroid hormones are slow. Think about it. I mean, I hope you remember from Bio One, the process of protein synthesis. You have to transcribe the DNA into messenger RNA. You have to translate the messenger RNA into a protein that happens in the ribosome. And while it happens, like, shockingly fast, if you think about, like, the fact that it's happening in my body right now, like a million times, that's really fast. But compared to our other mechanisms, you'll see that, whoa, it's actually kind of slow. That process takes a significant amount of time to end up with a functional viable protein. And here's the other thing that is true. There's a one-to-one hormone-to-product ratio. So essentially, I don't know how to say this, but one-to-one hormone-to-product ratio. And that just means if you want one protein produced to stimulate an action, you have to send in one hormone. And then it'll happen. If you want more protein, then you just have to send in more hormones. The only way to amplify the effect is to increase the amount of hormone that you've produced. So it's slow, and you can't amplify it. You can't, you can't, amplifying it is like, dude, let's take one hormone and, like, send the message to everybody in the whole world. Sorry, if you want the message to get out there, you have to, each hormone has to deliver the message personally. And that just takes a while. That's slow. That's why if you start taking steroids, you're not going to see a result tomorrow. You're going to see a result in a couple weeks because that's how long it takes for those steroid hormones to have an effect. Let's talk about amino acid derivatives. These guys are kind of a set of in-betweener hormones.