0:02 you have a small gland in your body that
0:05 weighs about 20 to 30 grams yet despite
0:06 its small size it has some of those
0:08 powerful effects over your metabolism
0:10 and how you utilize energy let me give
0:13 you an idea here when this gland isn't
0:14 secreting hormones in the proper amounts
0:17 your metabolism can fall as much as 40
0:19 to 50 percent below normal but on the
0:21 flip side if it's secreting too many of
0:23 the hormones metabolism can go up as
0:26 high as 60 to 100 above normal so
0:28 clearly this gland packs quite the punch
0:30 and the gland in question here is the
0:33 thyroid gland so in today's video we're
0:34 going to talk about how this gland
0:36 influences metabolism and how this
0:38 affects things like energy levels fat
0:41 weight gain and weight loss how it
0:42 affects your muscle tissue and even your
0:45 heart and can this thyroid gland
0:47 actually even affect sexual function
0:50 well we're about to find out so let's
0:52 jump right into this anatomical awesomeness
0:53 awesomeness [Music]
0:57 [Music]
0:59 so let's start by taking a look at a
1:01 real thyroid gland on this cadaver
1:02 dissection so if you take a look here
1:06 look how amazing this small little gland
1:07 here it's such a small gland to have
1:09 such powerful effects on the human body
1:11 you can see its proximity to the trachea
1:13 or the windpipe and we say that it's
1:16 inferior or below the atom's apple and
1:17 the Adam's apple is truly called the
1:19 larynx so this point right here that I'm
1:21 tapping with the probe is the same point
1:23 on me right there on my neck so
1:24 hopefully that gives you a pretty good
1:26 idea of where this gland would reside
1:29 now if we were to zoom in to the thyroid
1:30 gland tissue we would see that it's
1:32 primarily made up of these cells called
1:34 follicular cells and these follicular
1:36 cells are going to be what produces and
1:39 secretes the main thyroid hormones but
1:40 let's kind of take a step back for just
1:42 a second before we get into what these
1:44 thyroid hormones do and talk about what
1:47 actually activates this gland to do that
1:48 we're going to take a look at the brain
1:50 so here's A sagittal cut through the
1:51 head and we're definitely going to take
1:52 a look at some of the structures in the
1:54 central core here but first I want to
1:55 mention that we are going to play a
1:57 little bit of this game called telephone
1:58 and what I mean by that is that we're
2:00 going to find that a structure called
2:02 the hypothalamus is going to tell the
2:04 pituitary gland to tell the thyroid
2:06 gland to turn on or activate and we're
2:08 going to use an analogy or a little bit
2:10 of a comparison to help us with this and
2:12 some of you may have even actually lived
2:14 this comparison because sometimes dads
2:16 don't love it when people mess with
2:17 their thermostats and therefore the
2:19 overall temperature of the house so
2:21 we're going to say Dad tells the
2:23 thermostat to tell the furnace to turn
2:25 on or activate and hopefully that'll
2:27 help us more fully understand how the
2:29 thyroid gland gets activated here so
2:30 back to the central core of the brain
2:32 right where the probe is you're going to
2:34 see is the hypothalamus now the
2:36 hypothalamus the central core of the
2:38 brain does many amazing things one of
2:40 which has helped to maintain homeostasis
2:41 throughout the body and one of the
2:42 things that helps with this is to
2:45 regulate the thyroid gland so this
2:46 hypothalamus is going to secrete a
2:49 hormone called thyrotropin releasing
2:52 hormone or trh now as trh is going to
2:54 immediately diffuse into tiny little
2:55 capillars or blood vessels right around
2:58 the hypothalamus and travel down this
2:59 little nervous system stock in the blood
3:02 vessels here right to the pituitary
3:04 gland now that trh from the hypothalamus
3:06 is going to tell the pituitary gland to
3:08 secrete another hormone called thyroid
3:12 stimulating hormone or TSH that TSH is
3:14 also going to diffuse into surrounding
3:16 blood vessels and then circulate
3:17 throughout the body and eventually make
3:19 it to
3:21 the thyroid gland and that TSH from the
3:24 pituitary is going to tell the thyroid
3:26 gland to activate when we say activate
3:28 that means start secreting and producing
3:30 those main thyroid hormones so if we go
3:32 back to that analogy with the furnace we
3:35 would essentially say Dad the
3:38 hypothalamus secretes the trh to tell
3:41 the thermostat the pituitary gland to
3:43 secrete TSH
3:46 to then tell
3:47 the furnace
3:49 the thyroid gland to turn on and
3:51 activate and release its hormones which
3:52 is a pretty good analogy I think because
3:55 when the thyroid hormones start being
3:57 secreted increasing metabolism will also
3:59 increase body temperature furnace body
4:01 temperature it works now like I
4:03 mentioned when the thyroid gland is
4:05 turned on or activated it will secrete
4:07 the main thyroid hormones and these main
4:09 thyroid hormones have incredibly
4:11 powerful metabolic effects on multiple
4:13 structures and tissues throughout the
4:15 body now these main thyroid hormones are
4:16 called and I promise I'm not going to
4:17 give you too many more names throughout
4:19 this video but these main hormones are
4:23 called T3 and T4 T3 stands for
4:25 tri-iodothyronine and T4 stands for
4:28 Tetra iodothyronine so we're just going
4:30 to call them T3 and T4 but for those of
4:33 you who are interested try iodothyronine
4:34 that name comes from that the hormone
4:37 has three atoms of iodine where Tetra
4:40 iodothyronine that hormone has four
4:42 atoms of iodine so if you have an iodine
4:44 deficiency or if you don't have any
4:46 iodine you can't actually synthesize
4:48 these hormones and having an iodine
4:50 deficiency could cause all sorts of
4:53 thyroid related functional problems now
4:55 if a kid has an iodine deficiency that's
4:57 even a bigger deal because the thyroid
4:58 gland really gets involved in growth and
5:00 development throughout childhood so that
5:02 can cause delays in that development
5:04 those important developmental stages
5:05 throughout the beginning years of life
5:08 now luckily we only need about 50
5:11 milligrams of iodine per year to support
5:13 thyroid function and in most developed
5:16 countries the salt is iodized meaning it
5:18 just contains iodine so most of us don't
5:19 really have an issue getting the proper
5:22 amounts of iodine now another thing I do
5:23 want to mention kind of as an FYI
5:24 because I know I've mentioned a ton of
5:26 different names like thyrotropin
5:28 releasing hormone thyroid stimulating
5:30 hormone and now T3 and T4 if you wanted
5:33 to kind of simplify that and really
5:34 focus on it from say like a clinical
5:37 perspective like as a clinician with my
5:39 patients when I order thyroid tests for
5:41 them I usually just get a TSH to see
5:43 what the pituitary gland's doing and a
5:45 T4 to see what the thyroid gland is
5:47 doing and I'll kind of play a little
5:48 game with you guys at the end to kind of
5:50 show you how to analyze what's going on
5:52 with too much or too little of these
5:53 different thyroid hormones so we can
5:55 kind of figure out what's going on but
5:58 one thing we also need to cover here is
6:00 how these hormones are regulated but
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7:45 below so back to the regulation of these
7:47 thyroid hormones regulation of thyroid
7:48 hormones and just regulation of hormones
7:51 in general is very important and when I
7:52 talk about hormone regulation with
7:53 students and maybe you've heard me
7:55 mention this in previous videos with
7:57 hormone regulation we want the
7:59 Goldilocks principle and what I mean by
8:00 that is that we don't want too few of
8:02 the hormones not too many of them we
8:04 want them in just the right range
8:05 throughout the bloodstream and we can
8:07 use that thermostat and firmness analogy
8:09 again to help us with this let's say
8:11 that the house temperature is 69 degrees
8:13 and then Dad sets the thermostat to 70
8:15 degrees we all have a pretty good idea
8:17 that the thermostat is going to kick on
8:19 the furnace and tell what happens until
8:20 the temperature gets up to 70 degrees
8:22 and then it's going to shut off let's
8:24 apply that same information to the
8:26 thyroid hormones let's say the thyroid
8:28 hormone levels in the blood are a little
8:30 low the pituitary and the hypothalamus
8:32 will detect this and kick on the thyroid
8:34 gland to secrete more of those thyroid
8:36 hormones until they get up to the proper
8:38 levels and then it will shut off and so
8:40 this is a really awesome way to tightly
8:42 regulate these thyroid hormone levels so
8:43 you don't have a ton of fluctuations
8:46 because we all know that if we had a
8:48 really crappy heating system let's say
8:49 we set the temperature again to 70
8:51 degrees but the thermostat didn't kick
8:52 on the furnace until it was all the way
8:55 down to 50 degrees or the opposite end
8:56 of the spectrum it didn't shut off until
8:58 it was up to 80 or 90 degrees that would
9:00 not be a fun situation because the
9:01 temperature throughout the house would
9:04 be fluctuating like crazy but instead we
9:05 tightly regulate the house temperature
9:07 just like we would tightly regulate
9:10 those thyroid hormone levels so I think
9:11 we set the stage well enough now to
9:13 where we can finally start talking about
9:14 some of the specific functions of these
9:17 thyroid hormones now we've strongly
9:18 implied that the thyroid hormones helped
9:20 to regulate metabolism or in other words
9:22 help to increase metabolism but what
9:23 does that really mean and how should we
9:25 approach this well I think we should
9:27 start at the cellular level because if
9:28 we can figure out how these thyroid
9:31 hormones influence the metabolism of the
9:33 cells we can apply apply that to how the
9:35 cells process things like carbohydrates
9:38 and fats and even apply that to larger
9:39 structures like how does that affect
9:42 adipose or fatty tissue muscular tissue
9:43 and other tissues and structures
9:45 throughout the body and keep in mind
9:47 that your overall metabolic rate or your
9:50 basal metabolic rate is the totality of
9:52 the metabolism or how all the cells
9:54 throughout your body are processing
9:55 energy so looking at it from the
9:57 cellular standpoint or the cellular
9:58 perspective first kind of makes sense
10:02 and these thyroid hormones influence or
10:03 affect the majority of the cells
10:05 throughout the body and one of the
10:07 things that they do is help to activate
10:09 or turn on multiple genes and what we're
10:11 going to see is that the cell will start
10:13 building things it'll start building
10:16 things like protein enzymes structural
10:18 proteins transport proteins and other
10:20 substances and so if you look at it from
10:22 this perspective when the cell is
10:23 building all these different proteins
10:26 and other substances that's going to
10:28 require energy which will raise
10:30 metabolism of the cell if we take that a
10:32 little bit further
10:34 a lot of those proteins like the enzymes
10:36 and the transport proteins often require
10:38 energy to perform the work of the cell
10:41 that will also require energy and
10:43 therefore also increase the metabolism
10:45 of the cell another awesome thing that
10:46 the thyroid hormones do within the cell
10:49 is that they increase the size and
10:51 number of mitochondria and those of you
10:53 who know what the mitochondria is we
10:54 often nickname it the PowerHouse of the
10:57 cell because this little organelle helps
11:00 to utilize carbohydrates and lipids to
11:02 process ATP which is the energy currency
11:04 of the cell and if we're increasing the
11:06 metabolic rate of the cell we want more
11:08 ATP to support that increased metabolism
11:10 thyroid hormones have powerful effects
11:12 on carbohydrates it will increase the
11:14 rate at which cells bring in
11:16 carbohydrates it will also enhance
11:18 glycolysis which is when the cells take
11:20 glucose a type of carbohydrate and
11:23 utilize that to produce more ATP it also
11:25 enhances gluconeogenesis this primarily
11:27 happens in the liver and this is where
11:29 the liver produces more carbohydrates it
11:31 will also increase the rate at which the
11:33 carbohydrates are absorbed across the
11:35 gut and into the bloodstream so in
11:37 summary these thyroid hormones pretty
11:39 much stimulate or enhance almost all
11:41 aspects of carbohydrate metabolism not
11:43 only do these thyroid hormones help to
11:45 enhance the utilization of carbohydrates
11:47 they also help to enhance the
11:49 utilization of fats and what we'll see
11:50 is that the thyroid hormones will help
11:53 to pull fat from the fat storage in the
11:54 form of free fatty acids and these free
11:56 fatty acids can then circulate
11:57 throughout the blood and then be
12:00 utilized for energy by the cells now if
12:03 we're pulling fat from the fat storage
12:05 that will help facilitate weight loss or
12:06 at least help to maintain a healthy
12:08 weight when we have those normal levels
12:10 of the thyroid hormone now another cool
12:11 thing that the thyroid hormones do is
12:13 they will actually lower or bring down
12:15 cholesterol and triglyceride levels in
12:16 the blood and if you've ever had your
12:18 cholesterol tested you have a pretty
12:19 good idea that we don't want our
12:21 cholesterol levels to get too high so
12:22 let's have a little checkpoint here
12:24 because many of you are probably
12:25 thinking about the potential drawbacks
12:27 of having something called
12:29 hypothyroidism which is having too low
12:31 of the thyroid hormone and if we use one
12:32 of our previous examples if somebody
12:34 were too low with the thyroid hormones
12:36 their cholesterol levels could go up and
12:37 that could increase their risk of
12:39 certain cardiovascular conditions now
12:41 some of the obvious drawbacks is
12:43 metabolism is going to go down we're not
12:45 going to utilize carbohydrates as well
12:47 not going to utilize fats as well and
12:49 you'll often see weight gain with people
12:51 who have hypothyroidism now with many of
12:53 our students my patients and even in our
12:55 YouTube videos we often will talk about
12:57 diet and exercise and how much that can
13:00 influence weight gain or weight loss now
13:02 we definitely have some level of control
13:03 with weight gain and weight loss but
13:06 somebody who has hypothyroidism that
13:07 makes it even that much more difficult
13:10 to lose weight just with diet and
13:12 exercise so a lot of times when my
13:14 patients have a low level of thyroid
13:16 hormone they really like it when their
13:17 levels get to those normal ranges
13:19 because it makes it easier to shed some
13:20 of that weight now many people will
13:23 focus on the drawbacks of hypothyroidism
13:24 and they'll think just give me those
13:26 thyroid hormones increase my metabolism
13:28 and everything's going to be great but
13:30 remember the Goldilocks principle not
13:33 too few not too many just right there
13:35 are health conditions and drawbacks to
13:36 being hyperthyroid or having
13:39 hyperthyroidism and so it's not like
13:40 when somebody's hypothyroidism we just
13:42 jack up the thyroid levels to these
13:43 astronomical levels we get them to
13:46 within the normal ranges so as we go
13:48 throughout these other examples kind of
13:49 think of it from the perspective of okay
13:51 what would happen if I went too high
13:53 with the thyroid hormone versus if I
13:55 went too low the thyroid hormones also
13:56 have an effect on cardiovascular
13:58 structures as well as the heart due to
14:01 the increased metabolic activity many of
14:02 the blood vessels to the tissues will
14:05 vasodilate or open up delivering more
14:06 oxygen to accommodate that increased
14:08 metabolism as well as to be able to pull
14:10 waste products from the cells
14:12 metabolizing and creating those waste
14:14 products the heart will also contract
14:16 more forcefully as well as increase in
14:18 strength heart rate tends to go up with
14:20 thyroid hormone as well but again coming
14:22 back to our balance here if we had
14:25 hypothyroidism that would create less
14:26 contractility of the heart maybe
14:28 decreased strength also heart rate would
14:31 be lower if we had too much heart rate
14:33 would be too high and if you think of
14:35 somebody who had hyperthyroidism for
14:37 years and years and years and it wasn't
14:39 controlled eventually the heart can
14:41 start to break down the proteins within
14:42 The myocardium which is the heart muscle
14:44 will start to break down and you can
14:45 actually get things like myocardial
14:47 failure respiratory rate or breathing
14:49 rate will also increase with thyroid
14:50 hormones which makes sense to help
14:52 facilitate getting more oxygen into the
14:54 bloodstream to help accommodate the
14:56 increased metabolism we'll also see that
14:58 the gut motility how much the guts are
15:00 Contracting and moving food along
15:03 increases with thyroid hormone and so
15:05 somebody who actually has hypothyroidism
15:07 their gut motility will actually slow a
15:09 bit and things don't pass through as
15:11 quickly so they tend to actually get
15:13 constipated whereas somebody with
15:15 hyperthyroidism their guts are
15:16 Contracting more frequently and
15:17 forcefully and things are passing
15:19 through too quickly and they often will
15:22 get diarrhea thyroid hormones also
15:24 affect skeletal muscle tissues and with
15:25 slight increases of thyroid hormones
15:27 we'll see that the skeletal muscles will
15:29 contract a little bit more quickly and
15:31 vigorously but again with excessive
15:32 levels we we can have a problem with
15:34 hyperthyroidism because the skeletal
15:36 muscles can actually weaken due to
15:37 protein breakdown now with
15:40 hypothyroidism the muscles will actually
15:42 contract more sluggishly and react more
15:43 slowly and you're probably not going to
15:45 be surprised that thyroid hormones have
15:47 an effect on the nervous system and
15:49 normal levels of those thyroid hormones
15:51 have a positive effect on cerebral
15:54 function but excess amounts can cause
15:56 things like anxiety agitation kind of
15:58 feeling fidgety even some people have
16:00 experienced things like paranoia now if
16:03 they're too low or hypothyroid we can
16:04 get things like somnolence which is
16:06 feeling tired lethargic and just kind of
16:09 feeling blah and what about sexual
16:12 function of course the thyroid hormones
16:13 are also going to affect sexual function
16:16 so you're probably again not going to be
16:17 that surprised to hear me say we want
16:19 those hormones within the proper ranges
16:21 so that our genital structures in our
16:23 reproductive physiology works properly
16:26 now let's say a male has hypothyroidism
16:28 that could affect things or at least
16:30 cause decreased sex drive in libido
16:32 whereas hyperthyroidism could cause
16:34 impotence in a male impotence would be
16:36 an inability to get an erection with
16:38 females with hypothyroidism you could
16:40 also see a decrease in libido and sex
16:42 drive hyperthyroidism would tend to have
16:44 irregularities in the menstrual cycle
16:47 but you can also have irregularities in
16:49 the menstrual cycle with hypothyroidism
16:51 in females so looking at the menstrual
16:52 cycle alone is not a really good
16:55 indicator of hyper versus hypothyroidism
16:57 so hopefully that gave you a lot of cool
16:59 information on just how powerful the
17:02 thyroid gland in its hormones are and
17:03 how it affects multiple tissues and
17:05 structures throughout the human body now
17:07 as I mentioned earlier when I'm checking
17:09 for thyroid conditions on patients I
17:11 really focus just on two hormones when I
17:13 do a blood draw I usually draw the TSH
17:15 which is the thyroid stimulating hormone
17:17 released from the pituitary gland and I
17:20 really focus on the T4 which is one of
17:21 the main thyroid hormones secreted from
17:23 the actual thyroid gland now let me give
17:25 you a couple of scenarios to help you
17:27 kind of assess with these blood levels
17:29 like might mean let's say I have a
17:30 patient and I get the blood levels back
17:32 in the T4 from the thyroid gland is
17:34 really low but the TSH from the
17:37 pituitary is really high what that's
17:38 telling me is that we have a problem
17:40 with the thyroid gland because it's not
17:42 responding to the TSH telling it to turn
17:45 on and that would be called primary
17:46 hypothyroidism because we have the
17:49 problem with the thyroid itself let's
17:51 say in another scenario I have low T4
17:54 from the thyroid but also I have low TSH
17:57 from the pituitary gland that implies
17:58 that there's a problem with the
18:00 pituitary gland because the pituitary
18:02 gland isn't telling the thyroid gland to
18:04 actually turn on and do its thing the
18:06 thyroid's over here waiting like hey
18:08 pituitary I'm ready but the pituitary
18:10 isn't secreting the proper TSH to
18:12 activate the thyroid gland and that
18:15 would be called secondary hypothyroidism
18:17 let's go to another scenario let's say
18:19 the T4 from the thyroid gland is really
18:22 high but the TSH from the pituitary is
18:23 really low that would imply a problem
18:25 with the thyroid gland that the thyroid
18:27 gland is kind of Behaving on its own
18:30 without the TSH it's over secreting the
18:31 pituitary is like I'm not going to tell
18:33 you to turn on even more because we
18:35 already have too much of this thyroid
18:37 hormone that's almost like having your
18:39 thermostat set at 70 degrees for heat
18:41 but the temperature is already 85
18:43 Degrees your thermostat isn't going to
18:45 tell your furnace to kick on even more
18:48 in that scenario let me give you one
18:50 other scenario let's say the thyroid
18:52 gland or the T4 from the thyroid is
18:54 really high but the TSH is also very
18:57 high that's implying a problem with the
19:00 pituitary gland over secreting TSH and
19:01 then the thyroid gland is just following
19:04 suit being told what to do a lot of
19:06 times that's a pituitary tumor that's
19:08 secreting too much too much TSH that
19:10 scenario is kind of like you set the
19:12 thermostat in your house to 85 degrees
19:14 and the furnace is just kicking on to
19:16 obey the thermostat that so hopefully
19:18 that gives you some cool scenarios to
19:19 think about if you've ever got a thyroid
19:21 blood draw and hopefully you guys
19:22 learned some amazing things from this video
19:23 video
19:25 if you feel the need like always like
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19:29 if you're interested in athletic greens
19:30 we'll also have that information in the
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19:34 see in the next video [Music]
