Now Diabetes Mellitusis a group of disorders that’s caused by improperfunction of insulin which is a hormone responsiblefor regulating blood sugar or blood glucose. And this results in Hyperglycemia. But since Diabetes is a group of disorders there’s many different underlying pathophysiological mechanisms that can cause the disease.
And depending on which mechanismis occurring in someone the presentation of the disease can actually be very different. So before we get started, I want to briefly talk about the Pancreas. Now you can see here we havethe esophagus coming down and it dives behind the liver here. And then it goes into the stomach and then the stomach goesback behind the liver and comes out as the small intestine. And in yellow here, nestledin next to the small intestine and behind the stomach is the Pancreas. Now, the Pancreas isfrequently referred to as being comma shaped andyou can kind of get that. Oh, if you kind of turned it on its side it might look like a comma. But the way I like to rememberhow the Pancreas looks is by thinking about my favoriteprofessional football team which is the Minnesota Vikings. And I kind of think the Pancreas maybe it looks like the horns on the side of the Minnesota Vikings helmet. So whatever helps you rememberwhat the Pancreas looks like.
But regardless, the Pancreashas two main functions. And the first function is Exocrine. What this means is that thePancreas secretes Enzymes into the digestive tract whichthen chemically digests food and help your body absorbthe nutrients we eat. So it helps with digestion. But the Pancreas also hassome Endocrine function. And what this means isthat it produces Hormones. And specifically for the Pancreas these Hormones help thebody with Metabolism. But what does all thishave to do with Diabetes? Well, I mentioned earlierthat Diabetes Mellitus is caused by dysfunction of insulin which is one of these Hormonesthat the Pancreas produces. And in Type 1 Diabetes, certain areas of the Endocrineportion of the Pancreas are destroyed so that thePancreas cannot produce insulin. And Type 1 Diabetes is actually a relatively uncommon disease.
It affects about threeout of every 1,000 people in the United States. Now, let’s dive a littlebit closer into the Pancreas to get a better understandingof what’s going on. So the cells that are responsiblefor the Endocrine function of the Pancreas are locatedin regions of the Pancreas that are known as theIslets of Langerhans. So let’s just draw those in here.
So in these Islets of Langerhans there are two main cell typestypes that are responsible for producing Hormones. So in blue here, we have the Alpha cells. And the Alpha cells areresponsible for secreting glucagon. Then in green we have the Beta cells. And they’re responsiblefor secreting insulin. And as I’ve mentioned before, these two Hormones areresponsible for regulating much of the bodies metabolism. And one specific componentof this is our Blood glucose or our Blood sugar level.
So what happens is if someone, just say, you pretend you just had a meal and your body starts absorbingthe sugar from that meal. What’s going to happen isyour Blood sugar levels or your Blood glucose levelsare going to increase. And this increase in Blood sugar is sensed by the Betacells in the Pancreas and they’ll secreteinsulin into the blood.
And what it does is thatinsulin is then going to lower the Blood glucose level by causing the cells allover the body to take up and absorb the glucose so that they can then use it for energy. Or it could be stored in the liver. And either way, theglucose comes out of blood so the Blood sugar level lowers. Now if insulin where to act on its own, the Blood sugar levelor Blood glucose level would get too low. It would start to decreasefrom its normal level. And luckily the Pancreas sensesthis too in the Alpha cells or the blue cells hereand secretes glucagon. And what happens then is glucagon causes the Blood glucose level to raise, going back to normal.
And it does this by causing the liver to release the glucosethat’s stored there. So what does this allhave to do with Diabetes or specifically Type 1 Diabetes? Well, in Type 1 Diabetesthere is destruction of these Beta cells in the Pancreas so the body can’t produce the insulin. And if the body can’t produce insulin it’s not able to lowerits Blood glucose level and you have an unbalancedglucagon response. Which results in thisraising of the Blood sugar and this is known as Hyperglycemia. Hyper for high, glycemia for blood sugar. But what is the underlyingcause of this destruction of the Beta cells? I’m going to just slide this over so we can get a littlemore room to work on it. Well, Type 1 Diabetes isan Autoimmune disease.
And as you can imagine by the name it has something to dowith the immune system. And what happens is that someone who develops Type 1 Diabetes was born with a genetic predispositionto the disease. Now, this doesn’t necessarily mean that he or she had the disease at birth. But they just had something in their genes causing them to be more likelyto develop Type 1 Diabetes. Then over time there was somesort of Environmental trigger. And this part of the disease process isn’t quite as well understood. And it could be somethingpotentially like a virus, or some sort of toxin, or something else. But regardless, there’ssome sort of trigger that causes someone witha genetic predisposition to have this Autoimmune response or production of antibodies and T cells that then attack the Beta cells. And this is what causes thedestruction of the Beta cells in the absence of theproduction of insulin. Which is the underlyingcause of Type 1 Diabetes. And it’s this Autoimmuneattack of the Beta cells here that causes the Pancreas to not be able to produce any insulin. And when it can’t produce any insulin what happens is that the individual will develop Type 1 Diabetes. Well, let me just move over again so we can get a little more space to go through why symptomsdevelop in Type 1 Diabetes. All right, so imagine a blood vessel here. And this blood vesselis transporting glucose.
And in a normal individualwithout Diabetes this glucose is going to go to lots of different organs in the body. Such as the brain, andthe muscles, and maybe give them a little Popeyetattoo for good measure. As well as the liver, wherethat glucose can be stored. But unfortunately in Type 1 Diabetes the insulin isn’t presentto take the glucose out of the blood and helpit get to these organs. It gets blocked, almostlike the body is starving despite having all of this glucose. And so what happens is that the liver acts like it is starving and it releases its storedglucose back into the blood. And then just like the glucosecan’t get out of the blood to some of these organs, it also can’t get outand be stored in the fat or the adipose tissue,which I’ll draw here. And so what the fat does is to also kind of try and helpthe body create more energy is it breaks down into somethingknown as free fatty acids. Which I’ll just abbreviate FFA, which the body can thenalso use for energy. It’s this process here thatresults in the symptoms of Type 1 Diabetes. And the first one is what I’ll call “Starvation in the face of Plenty.” And by this I mean, the bodyalmost acts like it’s starving even though it has all of thisglucose present in the blood. And this results in symptomslike lethargy and fatigue. Because it’s trying to maintain the little glucose itthinks it has for the brain and the other organs thatare vital and really need it. So someone with Diabetes willbe lethargic and fatigued. And then the next thing that happens is, occurs in the kidneys.
Now, normally the kidneysreabsorb all of the glucose that’s in the blood and put itback in the blood when it’s, when they’re filtering the blood. But when this glucose levelgets so high from Diabetes it overwhelms the kidneys. And that glucose spills out in the urine. And this is known as glucosuriaor glucose in the urine. And glucose is anosmotically active soluble. What does that mean? Well, what it means is that ittends to draw water with it. So as the body peesout all of this glucose a lot of water comes with it. And this is known as polyuria or poly for kind of lotsor many and uria for urine. And this results in dehydration because you’re losingall the water and thirst. So, someone with Type 1 Diabetes is frequently going to present with being tired and fatigued, going to the bathrooma lot and dehydrated. And unfortunately, for some individuals, if they get sick whenthey have Type 1 Diabetes before it’s been diagnosed, the body can’t compensate for the stress and you can get a life threatening disease that’s called Diabetic ketoacidosis or DKA which is a life threatening form of dehydration and acidosis.
When it comes to diagnosisabout 70% of individuals with Type 1 Diabetes willbe diagnosed in this stage before it gets too bad. Bit unfortunately,about 30% of individuals who are diagnosed with Type 1 Diabetes actually have Diabeticketoacidosis or DKA, as their presenting symptom. So this is just a briefoverview of Type 1 Diabetes which is an Autoimmune disease. Meaning that there’santibodies and T cells that destroy the Betacells of the Pancreas so that the Pancreascan’t produce insulin, resulting in Hyperglycemiaor high blood sugar. And it’s this high blood sugar that results in all of thesymptoms of Type 1 Diabetes.