Endocrinology | Growth Hormone

all right Engineers what we're going to do in this video is we're going to talk about growth hormone so growth hormone we discussed a little bit about um we haven't really got to the complete detail of it yet but we know specifically in the hypothalamus there's some specific hormones that are being made right so for example if we look here in the hypothalamus here's the hypothalamus and the hypothalamus has a specific nucleus situated in there that's actually releasing this really really really potent and Powerful hormone and this hormone is called growth hormone releasing hormone and

if you remember what was the growth hormone releasing hormone do uh doing it was actually circulating through the hypoy portal system which is this circulatory vascular connection between the hypothalamus and the anterior pituitary or we can call it the Adeno hypothesis right so it circulates down through the primary capillary plexus through the intermediate hypophysial portal vein and then out through the secondary capillary plexus and then what it'll stimulate what what's this actual green cell right here called what is this green cell here called this green cell here is actually called a somatrope somatotrope a somatotrope

when it responds to the growth hormone releasing hormone will secrete out into the bloodstream this very very very important hormone that we're going to spend most of our time you're talking about and that is growth hormone so this is actually growth hormone now real quick ghr because it's actually being released what's some of the secondary triggers that can cause ghr to be released so what are some other things here that are causing this actual release so you know growth hormone it's actually stimulated by a couple different things let's actually note them so let's say here

let's actually number them so let's say what's stimulating it so let's say here in this these actual black column we're going to say the things that are stimulating it so one of the stimuli is actually going to be um we could actually say high amino acid levels in the blood in the blood that's one and I'll explain why that's a strong stimulus another stimulus here is actually going to be low glucose levels in the blood okay so we could say hypo glycemia right that's another word for this low glucose in the blood another stimulus is

low fatty acid levels in the blood okay so low fatty acids in the blood another very very potent stimulus of the growth hormone is going to be exercise that's a huge one exercise is a very strong stimulus and even we can say certain types of healthy stressors right so certain types of healthy stressors okay because not all stress is a bad thing so certain types of healthy stressors okay these things right here could be the very driving force to start causing this growth hormone releasing hormone how they could be utilizing this mechanism by what stimulating

this nucleus here which we haven't even said what this nucleus is this nucleus is a very very potent nucleus and it's actually releasing other hormones besides growth hormone releasing hormone so that's why it's important to know what are the primary stimuli um and these triggers that can actually cause growth hormone release well the actual nucleus here is actually called the arcu nucleus it's called the arcu nucleus okay so this nucleus right here is called the arcuate nucleus and again what's stimulating it high amino acid levels in the blood hypoglycemia hypolipidemia EX exercise and certain types

of healthy stressors and it's causing ghrh release which is stimulating the somatotropes to produce GH Okay now what's the function of GH well growth hormone is actually going to have a specific organ a Target organ that it's going to go to first okay so some of it will actually come to this target organ some of it will actually go into the blood triom so let's show it bifurcating so it's like I'm going to go this way and then the other way can actually go and it can actually bind right into this receptor right here so

let's say it binds into this receptor right here so let's say here's the growth hormone we'll draw it as a actual green circle here let's say it's this green circle and it binds on to this receptor and actually this is a h specific type of receptor um it actually is going to activate a like kind of like a tyrosine kinas receptor it's kind of like a tyrosine kyes receptor and what it does is there's a specific part whenever growth hormone binds onto this receptor it activates this phosphorilation of specific types of amino acids on this

inner part of this receptor and what it does is there's this this enzyme that's activated here and it's called jonis kyes but we just actually denote it as Jack so jonis kyes is Jack and he's the one that's undergoing this phosphorilation right and when Jack causes this phosphorilation another thing that he can do is he can phosphorate this uh specific type of U transcription factor and that transcription factor is actually called stat so here we got Jack this Jack is activated and what does Jack do so let's say here we we Square we we kind

of saw this is stat Jack actually come over comes over here as a jonis kyes and he can add phosphates onto stat what is stat stand for it stands for Signal transducer activator of transcription so what do you think he's going to do he's going to come in here and he's going to bind onto a specific sequence of DNA a gene sequence of DNA right and when he binds onto the specific Gene sequence it's going to undergo transcription and it's going to produce what mRNA then after the MRNA it'll actually go to a what a

ribosome and then that ribosome will do what with the protein I me with the actual Mna it'll translate the MRNA when it translates the MRNA it actually gets converted into a protein and then it can go through multiple different types of other processes so again what is this right here this is our protein and it'll undergo some modifications in the rough VR and the GOI but eventually it'll be pushed out into the circulation what is this protein that we actually secreted this protein is actually going to be called insulin like growth factor so we got

insulin like growth factor type one okay so it's making insulin like growth factor type one okay why am I mentioning this because I showed you here right growth hormones kind of making a little detour here so let's say you know he's he's he has this little fork in the road here so what's this fork in the road right so he has a little Fork on the road and he's some of him is actually going to go this way so a certain percentage of him is actually going going to go into the bloodstream and go exert

its effects on target organs some percentage of them is actually going to go over here on the liver and activate what's called this Jack stat Pathway to lead to the production of insulin like growth factors okay what's going to happen now so let's say here we have our growth hormone let's focus on the effects of insulin light growth factor first okay insulin light growth factor can do a lot of different things okay one of the big things he's going to do is he's actually going to go and promote a lot of protein synthesis how so

you see this muscle cell right here what he's going to do is he's going to come out here he's going to come out of the bloodstream so let's say here he comes out of the bloodstream and he comes over here and he binds on to this receptor right here let's actually draw him as um let's draw him as green again let's say he's the green molecule right so let say here we have insulin light growth factor one he binds onto this receptor present on the muscle cells skeletal muscle right what does he do he activates

specific signaling Pathways so he'll activate specific signaling Pathways and let's say inside here the muscle cell here's the actual nucleus it activates specific genes and produces specific types of proteins and what are these proteins going to do these proteins are going to come over here and maybe phosphorate or do some specific type of mechanisms to these channels right here these green channels guess what these green channels are for they're for amino acids what do we say was really high in the blood in order for the stimulus to occur we said that there was elevated levels

of amino acids well what are we going to do with these amino acids well growth hormone is stimulating what he's stimulating these channels to open and guess who these channels are specific for amino acids and guess what's going to happen with these amino acids they're going to get taken into this muscle cell another thing that's going to do is this isn't the only pathway it can stimulate it can stimulate another pathway it's going to stimulate another pathway here which is it's going to take these amino acids and it's going to convert these amino acids and

cause them to get linked up and when it links up a lot of these amino acids it's going to link these amino acids together and produce what's called proteins so what are we going to get out of this we're also going to get proteins and what kind of proteins could be many many different types of proteins it might be proteins that are going to be like myofibrils like actin and myosin and other different types of cytoskeletal proteins and what is that going to do to the overall size of the muscle it's going to increase the

muscle size right so what's the overall result of this The increased amino acid uptake and increased protein synthesis can lead to increase muscle size right so might te lead to hypertrophy of the muscles so it's going to increase the overall muscle size and muscle function that's that's a beautiful thing there there okay so it's going to stimulate amino acid uptake and increase protein synthesis which can increase the muscle size and function that's one thing that this guy can do what's another thing you can do so let's say that I take a look here at the

bone so let's say insulite growth factor comes over here also okay so Insite growth factor also decides okay I'm going to come through this way also so I'm going to come through here and I'm going to exert my effects on some specific parts of the bone all right so what was this insulite growth factor doing it was coming over here here and on the bone you know you have a bunch of different cells within the bone what are these cells that we're going to focus on specifically in the bone there's going to be what's called

osteoblast and Osteo class what this actual growth I'm sorry this insulin light growth factor is going to do is it's going to be able to work to regulate the activity of these two cells so what it's actually going to do is it's going going to be weird it's actually going to increase the activity of both of these cells so it's going to increase osteoblastic activity and it's going to increase osteoclastic activity so it's going to increase bone deposition and Bone resorption and what's the overall result it's going to play a very very crucial role within

bone growth but it also we could actually even be more specific within the bone not only does it increase osteoplastic activity and increase osteoplastic activity is it plays a very very important role with what's called endochondral oifc okay so it plays a very very important role with Endo condr acific so one of the things that you're going to see out of this is that there's going to be an increase in like the bone mass right so the Bone's going to be a little bit thicker it's going to be bigger you're going to have this an

increased endochondral oifc process another thing that it's going to do what's other components of the bone it's also going to stimulate protein synthesis what is it going to stimulate the protein synthesis of what's the type of collagen that's present inside of our bone collagen type one okay so you can actually have a lot of collagen type one in here so let's say here we can actually put here in red we're going to have a lot of collagen production and again what type of collagen is actually being produced here collagen type one so we're going to

be producing a lot of collagen type one so that's going to increase okay so that's that part so what's the process of bone uh working on the bone it's going to increase the collagen type one it's going to increase osteoblastic activity it's going to increase osteoclastic activity but they're going to be highly regulated which is going to enhance the endoc condr oifc response what's another thing that this is actually going to do there's not just that proteins you know there's other things there's what's called proteoglycans so it's going to increase the production of what's called

proteo glycans and these are also extremely important in bone also okay so let's just remember that overall in the bone what's the overall effect in the bone it's going to increase the overall production of type 1 collagen increase proteoglycans highly regulate and increase the activity of both of your osteoclast and osteoblast to where they can enhance the endochondral osificante okay let's say here again we have the bone and then what part of the bone are we looking at specifically for this part here we're looking at the what is this part here this is called the

epiphysial plates right so this is your epiphysial plates okay because you have your diaphysis then you have your epiphyses and this is the epiphysial plate here on the ends what is this insulin like growth factor doing here insulin like growth factor one is also acting on on this right here what is it doing here you know what's actually going to be some of the main cells inside of this is actually cartilage here you're going to have a lot of condra sites so you're going to have a lot of condr sites guess what this actual insulin

like growth factor is going to be doing to these condra sites it's going to be increasing the differentiation the size the hypertrophy proliferation of all of these condra sites so what is it doing it's increasing the let's actually write this down what is it doing it's increasing the differentiation okay it's increasing the size okay and it's in it's causing increase in proliferation why are we doing this because you know what's called interstitial growth you have what's called inter stitial growth of the bone right where it's increasing in in length because you have appositional which is

increasing in width and you have interal which is increasing in length what growth hormone is doing is it's causing these actual condra sites or condra blasts really to start proliferating right so they start proliferating well actually they get bigger in size they hypertrophy all right so they get bigger in size they start proliferating excessively and then what happens is these layers let's say here's this is this is the part of the bone down here let's say down here is the bone and up here is the part of the bone right what's going to happen is

there's actually going to be osteoblasts which are going to be chasing this cartilage right so as we continue to keep proliferating these guys and getting them bigger and bigger and hypertrophying and stuff like that down here is where they're differentiating so this is actually going to get turned into bone and Bone and to bone into bone so what is it helping the actual bone to do to increase in length so it enhances the interstitial growth right at the epiphysial plates so it's increasing the actual condr blasts proliferation their hypertrophy they're increasing in size and also

it's causing them to differentiate into certain types of bone tissue okay so what do we have here for cartilage it's increasing interstitial growth what is it doing for bone it's increasing the osteoblastic activity osteoclastic activity which is enhancing the endochondral oifc response is making more proteins like collagen type 1 more proteoglycans which is being able to increase the actual density of the bone and helping to have more thick bones right and then what else is it doing here in the muscle it's increasing amino acid uptake into the muscle cells and it's activating genes to uh

trigger the protein synthesis process okay now that we've done that we've looked at the effects of insulin like growth factor one it's causing a lot of effects specifically on the bones the muscles and the cartilage now it also does have some extraskeletal effects but let's look at the growth hormone real quick you know growth hormone he loves to act on the liver so he also has other you know not only does he actually work through this Pathway to stimulate the production of insulin like growth factor one but you know he also can act let's actually

show it over here here this is also going to act to be able to do some specific process what is this process that he's also going to stimulate here he can also stimulate what's called gluco neo genesis what's the overall effect of glucon neogenesis it helps to be able to increase the blood glucose levels how are you making this glucose from non-carbohydrate sources where's those non-carbohydrate sources coming from let's let's track this growth hormone all the way over here to the adapost tissue so this is our adapost tissue right here right this is the atopos

what this growth hormone is going to do is it's going to bind on to these receptors here right so here's a receptor here here's a receptor here what's it going to do it's going to trigger this intracellular mechanism right activating an enzyme called hormone sensitive lipase what's that hormone sensitive lipase going to do the hormone sensitive lipase is going to act as that cutter we talked about right it's going to start breaking down what this actual triglycerides when it starts breaking down these triglycerides here it's going to break down the triglycerides into two components what

are those two components one of the components is actually going to be glycerol what's the other component that we're actually going to make out of it fatty acids right so we're making two components out of this what's that glycerol actually going to be good for it's actually going to be good for the process of gluconeogenesis we actually use that in order to make glucose so that's one of the things that growth hormone can do is it can come over here act on adapost tissue and increase this process right here which is called what is this

process called when you break down triglycerides into glycerol fatty acids it's called lipolysis right then what happens the breakdown products of lipolysis like glycerol can actually be used in the liver to make glucose that's called gluconeogenesis right we said before that odd chain fatty acids sometimes odd chain fatty acids can some of them can also get converted into glucose uh for glucogenesis but we're like we're saying here we're going to stick primarily with talking about uh specifically just the glycerol for this case but just if you want to know for your own personal interest yes

odd chain fatty acids can be converted into glucose but this is the mechanism that we're going to talk about so again glycerol to glucon glucose via gluconeogenesis is one of the effects of growth hormone lipolysis is a lipolysis is an effect of growth hormone also okay and growth hormone can also activate amino acid uptake also so we could also say here if we show with this blue representing the growth hormone he could also act on that receptor to increase the amino acid uptake into the muscle cells okay so now that we've done that let's just

go over really quickly here on this board what's the overall effects of growth hormone and what's the overall effects of insulin like growth factor insulin like growth factor one and then growth hormone let's write down their effects real quick so he was doing what he was stimulating the muscles right so he was acting on the muscles he was acting on the bones he was acting on the cartilage he can also do certain types of metabolic functions as well but we're going to stick to this what was he doing in the muscles he was working working

to be able to do what increase amino acid uptake and he also increased protein synthesis right so he's helping with the muscle growth right so the muscle hypertrophy and the muscle growth what is it doing for the bones doing a lot of stuff right increasing Osteo I'm going to put OB for osteoblastic activity it was also increasing osteoclastic activity it was increasing collagen type one production okay so collagen type one you know how you can actually remember how collagen type 1 is actually the main collagen in the bone you know how you spell bone b

o n e look one okay so collagen type one is the type of collagen in the bone okay so collagen type one another thing is actually going to be besides collagen type one we also said it could be increased proteoglycans right so a lot of stuff like that and then the increase in osteoblastic and Osteo classtic activity assisted in what's called Endo condal oifc okay we're going to put growth hormone obviously to the left now all right now we talk about cartilage what is it going to do for cartilage we already said for cartilage it

was going to increase the proliferation right so it's going to increase the proliferation of the uh condra blast of the condra blast it was going to increase the size of the condra blast we said that it was also going to increase the differentiation right so in other words the condra blast would be converted into specifically um it would actually be converted the cartilage the tissue would eventually be converted into bone tissue so cartilage would eventually get converted into bone tissue so differentiation of ctil like we'll say the condr sites or the condr blast right so

the condro blast So eventually this would actually lead into bone tissue right and what's the overall result of this an overall result was an increase in the interstitial growth interstitial growth which increases the length of the bone so we could say with this would increase the length of bone all right what do we say was the effect of growth hormone what we said the effect of growth hormone was on the liver and it was on the atap POS and it was also on the muscles what is it doing it's working on the liver to be

able to increase what's called gluco neo genesis it's also working on the liver to increase the insulin like growth factor one production it's also going to act on the atopos tissue and when it works on the atap post tissue it enhances what's called lipolysis and it's also going to work on the muscle tissue and in the muscle tissue it's going to help to be able to do increased amino acid uptake