Hypothalamic Pituitary Hormones

hi everyone Dr Mike here in this video we're taking a look at the hypothalmic pituitary axis and all the various hormones produced let's take a look now to begin you can see I've drawn this uh image up here it is not what you think unless you think it's the hypothalmus and pituitary gland then in that case it is what you think we are looking at an area of the brain highlighted here in Red so I've taken the brain we're looking at it from a side on leral view we've sliced it down the middle now is

that A sagittal view is that a coronal view different topic but it's a mid sagittal view taking a look in and there you can see deep and inferior to the brain we've got the hypothalmus and the pituitary gland so let's just label it up here we've got the hypothalamus up here now hypothalamus means below the thalmus so here we've got the thus the thus is the relay center of the brain any sensory information that comes up from obviously your sensory receptors that you need to be conscious about or aware it must go through the thus

that's an a side point so we've got the hypothalmus here and Below we've got the th uh the pituitary gland now sometimes the pituitary is also referred to as the hypothesis the hypothesis so hypo again meaning below and fisis means growth it's the below growth now if we have a look you can see there's two loes of the pituitary gland on this side we've got What's called the anterior lobe of the pituitary gland and on this side we've got the posterior lobe of the pituitary gland here we've got a stalk called the infundibulum isn't that

a great name infundibulum in in fulum and what we have is the hypothalmus communicates to the pituitary gland anterior and posterior to tell them to release hormones the hypothalamus is known as the master regulator of the endocrine system and if we think about why that's the case it's because it either releases hormones or stimulates the pituitary gland to release the hormones that can travel through the bloodstream to the body if we take a a look here what we've got is I said that the uh pituitary gland can also be called the hypothesis the posterior pituitary

can also be called the neuro hypothesis neuro hypothesis and the anterior is sometimes called the adino hypothesis adino hypothesis so we know hypothesis means undergrowth adino means gland all right the gland undergrowth and neuro means nervous right nervous tissue neural tissue why is that let's take a look how does the hypothalamus communicate firstly with the posterior Petry the hypothalamus will have neurons in particular nuclei and these neurons will project to the posterior pituitary so here we've got these neurons projecting down to the posterior pituitary if we have a look at the anterior the hypothalamus again

has neurons because it's nervous tissue that will project into an area called the median Eminence so that's called the median Eminence median eminence and here at the median Eminence these neurons are going to communicate with a blood supply and this blood supply will travel down to the anterior pituitary this blood supply is called the hypothal portal system hypothal portal system sometimes called portal vein let's call a portal system and then it communicates to the anterior lobe of the patry see the difference posterior is all nervous tissue and anterior has nervous to a blood supply and

then where does it go to here to more tissue so we're going to have cells here which makes up endocrine tissue because these cells uce and release their own hormones hence adino it's a gland both of these will release hormones into the blood supply of the body so let's just have that just indicating it's being released into the bloodstream of the body there we go so both of these result in that all right now we can have a look the posterior Petry is called the neuro hypothesis not just because of those neurons but because embryologically

the posterior p is an extension of the hypothalmus it's an extension of the brain of nervous tissue but the anterior pituitary is not it originated from elsewhere in the body and snapped on to this particular area and that's why it's called the adino hypothesis it's important to know this because their regulation is obviously going to be different let's first start with the posterior Petry the posterior Petry has two major hormones that it releases now these hormones are going to be produced at the hypothalmus travel down these axons and get released into the bloodstream to go

to the body and these hormones include what's called anti diuretic if I learned how to spell properly anti- diuretic hormone sometimes termed ADH sometimes in the US it's called vasopressin or Arginine vasopressin but I'm not in the United States I'm in Australia and the other hormone that it releases is oxytocin which you've probably heard colloquially as the love hormone again these hormones are reduced in the hypothalamus and are sent down these neurons when the hypothalamus is stimulated to tell them to release them into the bloodstream and that's how we get them released what do these

hormones do so antidiuretic hormone anti means opposing diuretic diuresis means to lose water right so lose water or to pee so it's an antip hormone so it travels to the kidneys travels to the kidneys specifically it travels to the nefron or the nephrons of the kidneys so they're the tubes so if we to draw up a nefron right there's a little Pac-Man head there's the proximal convoluted tubule there's the descending limb ascending limb distal convoluted tubal and then you got the collecting ducts so we're going to have antidiuretic hormone putting in little holes in the

distal convoluted tubu and the collecting ducts and these little holes are called aquaporin aqua porin and they allow for us to pull water from the nefron back into the body so we it allows for us to re absorb water meaning whatever comes out here comes out as P right but if we're pulling that water back well it's the antip hormone we're taking water out of what will ultimately become our urine when would this get released in times of dehydration so think about it if this is your body this bucket and you've got a certain amount

of fluid in your body and you've got a certain amount of things dissolved in that bucket but you dehydrate so you lose water you don't lose those solutes the things dissolved in it but you lose the water but you've got the same number of solutes but it becomes more concentrated so this increased concentration or increased osmolarity or osmolality that's another conversation that increased basically concentration surrounding your cells that's what stimulates the hypothalmus to trigger the release of antidiuretic hormone what about oxytocin oxytocin tells smooth muscle to contract so it tells smooth muscle to contract now

the smooth muscle specifically referring to here is the uterus and the muscles of the uh lining the ducts of the mamory tissue so this helps in labor so helping get bub out and this helps for milk ejection so this oxytocin how does that get stimulated all right think about this a mother is giving birth as the baby's head moves through the birthing Canal its head stretches the cervix that cervical stretch stimulates the hypothalmus to release oxytocin oxytocin gets released and tells the uterus which is behind the cervix to contract which helps push bub out as

bub continues to push it continues to stretch the cervix continuing to stimulate the hypothalmus to release more oxytocin Contracting the uterus more and you've got a positive feedback mechanism until bub is pushed out with the milk ejection it stimulates the tissues to contract the mamory tissue to squirt the milk out and that's milk ejection now you might have heard of it as being called The Love hormone it does play a role in solidifying relationships both positive and negative so that is the posterior pituitary they're the the two hormones now anterior gets a little bit more

tricky because the hypothalamus is going to produce and release hormones that it drops into this hypothal portal system and then these hormones must stimulate this gland to release more hormones so in unlike the posterior where we've got one set of hormones that gets produced and then released we've got one set produced released and then another set produced and released let's take a look at those so firstly let's have a look at the hypothalamic hormones so let's take a look first now this is in no particular order the first one is going to be what's called

gonado tropen and I'm just going to write RH for releasing hormone Gat tropen releasing hormone you might sometimes see it written as G lowercase n RH the next is going to be I'll do it in a different color growth hormone releasing hormone sometimes written as G HR H another one is going to be cortico tropen releasing hormone sometimes written as c r h I wrote that as two but that's number three and then number four we've got thyro tropen releasing hormone sometimes written as trh now there's actually other hormones produced here these are the stimulatory

ones so I can actually write a little plus sign next to all these cuz they're stimulatory but there are inhibitory ones for example the two inhibitory ones that you should know are going to be growth hormone inhibitory factor or inhibitory hormone inhibitory hormone and then the other one is Prolactin inhibit Factor now they've actually got additional names so the growth hormone inhibitory hormone is also known as somatostatin somato Statin and prolactin inhibitory factor is also known as dopamine and these are inhibitory growth hormone inhibitory uh growth hormone inhibitory hormone obviously inhibits growth hormone and prolactin

inhibitory Factor obviously inhibits not dopamine but oh prolactin which is going to be talking about here all right so we've got 1 2 3 4 and then these ones here let's look at these firstly G tropen releasing hormone if you see can you see G tropen corticotropin thyro tropen this suffix tropen means it's a hormone that's going to another gland to tell it to release another hormone which one doesn't hm you've got growth hormone releasing hormone right that's just going to go tell growth hormone to be released but gadat tropen releasing hormone is going to

go down here to tell the Gat tropins to Rel be released which go to another gland to tell more hormones to be released that's what the tropen refers to so let's start with one the Gad tropin are released produced and released by the hypos travel down these axons to the median Eminence and they jump into the hypothal portal system where they travel down and then these gonat tropin stimulate at these at this endocrine tissue here in the anterior pituitary to release the Gat tropins so let's write this up let's draw a line here so we

don't confuse these CU these are the hypothalamic ones I'll draw this line like this there we go all right so let's do number one going atat tropen releasing hormone what is that stimulating the release of it's going to stimulate the release of what we call the gado tropin and there's two gadat tropin there is what's called lutenizing hormone and follicle stimulating hormone lutenizing hormone is sometimes written as LH and follicle stimulating hormone is sometimes written as FSH so these hormones are released by The this tissue here in the anterior pituitary and they will travel down

and where do they go to they go to the gonads so the gonad tropin go to the gonads now the question is what are the gonads the gonads are the testes and the ovaries and what do these hormones do well they're named after what they do in the female reproductive system so what they do in the ovaries lutenizing hormone stimulates ovulation lutenizing hormone stimulates ovulation in the female and follicle stimulating hormone stimulates f icle development follicle development now if you think about so I've done a number of videos about the female reproductive system you've got

the 28 day on average cycle where the oite the egg needs to develop now in order for that egg to develop it needs to be surrounded by cells that keep it happy and healthy and nourish it those cells are called follicle cells so at the beginning of this cycle you have follicle stimulating hormone being released to help the development of of those follicle cells to look after the uite which is one of the reasons why the first part of the female reproductive cycle first halfish is called the follicular phase right then just before day 14ish

lutenizing hormone is released the egg ovulates and is released and that's why this is called the luteal phase all right in addition these hormones in doing this process stimulates more hormones to be released like estrogen and progesterone so estrogen and progesterone are released off the back end of this now what do they do in the testes lutenizing hormone in the testes stimulates testosterone to be released and follicle stimulating hormone in the testes stimulat sperm production all right so that's the gonadotropins stimulated by the release of gonadotropin releasing hormone when growth hormone releasing hormone is released

and travels down here it's going to release growth hormone so now we've got the release of growth hormone now what does growth hormone do well growth hormone sometimes just written as GH goes to pretty much every tissue of the body there's receptors for growth hormone everywhere and so growth hormone goes to nearly all tissues and stimulates growth and development what type of growth so uh protein synthesis bone elongation things like that so that's an easy one then we've got corticotropin releasing hormone corticotropin releasing hormone let's write this one no we'll keep it down here cordico

tropen releasing hormone sorry that's the one up there corticotrope releasing hormone travels down and stimulates the release of adreno cortico Tropic hormone oh my gosh that's a mouthful let's break it up so it makes sense adreno tells you the adrenal gland cigo tells you it's the cortex of the adrenal gland Tropic tells you more hormones are going to be released so goes to the adrenal cortex to tell it to release more hormones what is the adrenal cortex this is the adrenal gland so let's draw it up here if I've got my kidney and on top

there's the Hat of the kidney which is the adrenal gland so here's the adrenal gland the the adrenal gland can produce and release a number of hormones one of those hormones is called cortisol another one of those hormones is called aldosterone and another one of those hormones are called the androgens these are sets of hormones now cortisol fits under an umbrella of hormones called the glucocorticoids gluco corticoids and aldosterone is the sits under the umbrella of minello corticoids and the androgens are the sex hormones I've done a whole video on the sex hormones as well

now corticotropin releasing hormone released goes down the pil portal system stimulates the uh the tissue in the anterior pul Tre to release adrenocorticotropic hormone whoop and then that goes over to the adrenal gland and stimulates the release of cortisol aldosterone and androgens what do they do well cortisol known as a glucocorticoid plays around with glucose levels Corto is telling you it's at the cortex and the oid tells you it's a steroid so it's a steroid hormone that plays with blood glucose levels in times of stress or fear you release cortisol and what what it does

is it mobilizes glucose into the bloodstream so increases blood glucose why so that we've got the energy available so that we can repair or utilize it after the stressful situation aldosterone Minella corticoid because it's a steroid hormone produced by the cortex that plays around with an important mineral called sodium and what it does is it increases sodium reabsorption we draw up the nefron here what this does is it helps us reabsorb sodium so we throw now sodium back into the body throw sodium back into the body why is that important because remember water being a

hydrogen with two oxygen the oxygen is slightly negative charge the hydrogen is slightly positive charge it loves charges which means wherever sodium goes with its positive charge it's going to pull water with it so if I reabsorb sodium I reabsorb water and therefore lostone gets released when we want to increase our blood volume so we want this to get released when we want to increase our blood volume that's the desire okay the increased blood glucose here is for uh help us regenerate I suppose is one way of putting it um after a stressful situation now

the Androgen sex hormones don't stress cuz they're not a major releasing factor that happens here these two are in response to adrenocorticotropic hormone number four thyrotropin all right so thyrotropin this one's an relatively easy one number four thyrotropin releasing hormone goes down and releases what we call thyro it's got two names thyrotropin thyrotropin but more commonly it's called thyroid stimulating hormone stimulating hormone thyroid stimulating hormone often written as TSH and that's important because when you look at blood levels of TSH that can help you with Hyper or hypothyroidism what does this hormone do once it

gets released by the anterior pituitary it travels to the thyroid gland and tells the thyroid gland to produce thyroid hormone which is T4 and T3 now T4 is the most is what the one that's produced the most but actually converts to T3 at the tissues therefore T3 is the active one triiodothyronine and it's important because what does thyroid hormone do it helps regulate metabolism among other things but yes regulate metabolism which makes sense because if you increase the amount of thyroid hormone you increase your metabolism when you increase metabolism you use energy right so you

lose weight you sweat these are some of the side effects if you don't have enough you slow metabolism which means you hold on to nutrients and you gain weight and you can feel cold because you're not generating the heat from metabolism so that's what the thyroid stimulating hormone does here now the other two so matter statins easy if if we don't want to uh if we don't want to release growth hormone we release somat Statin it inhibits that growth hormone somat Statin gets released says no more growth hormone thank you very much prolactin is the

fifth one that gets released it's the only one that doesn't have a stimulatory factor prolactin is the only one that doesn't have a stimulatory factor practin prolactin again gets released by these cells in the anterior pituitary and it promotes it's in the name it's promotes lactation right it's Pro lactation so stimulates milk production not ejection because that's oxytocin but milk production that's practin here's how it works prolactin will pretty much always get released right so prolactin will always get released to some level but dopamine right is going to be released to inhibited it so when

we don't want to produce milk dopamine is constantly inhibiting these cells of the anterior pituitary to say no prolactin thank you very much but once you get suckling at the nipple from an infant this suckling inhibits the dopamine so if you inhibit the dopamine there's no dopamine being released here and then the cells of the anterior py are free to make as much prolactin as they like so that is stimulated by suckling suckling is the positive regulator of that all right right that is an overview of the hypothalamus its hormones and the pituitary hormones as

well I hope that makes sense I'm Dr Mike hi everyone Dr Mike here if you enjoyed this video please hit like And subscribe we've got hundreds of others just like this if you want to contact us please do so on social media we are on Instagram Twitter and Tik Tok at Dr Mike todorovich at d m i k t o d o r o v i c speak to you soon