So, diabetes is a very common disease.
It affects nearly 10 percent of the population
and more than 25 percent, or one in four people
over the age of 65 have diabetes.
But what exactly is diabetes mellitus?
Let me start by going through a couple of scenarios.
Now the first scenario I wanna talk about
is that of Joe here.
So let me bring in Joe.
Now Joe is a 15 year old boy.
Over the past few months
Joe just really hasn't been feeling well.
He says, you know it's hard to
kind of put his finger on it,
but he's in general been a little bit
more tired and fatigued than usual.
In fact, it's caused him to lose a little bit of weight
and he's already kind of a skinny guy to begin with,
so that's definitely something that's abnormal for him.
And you know his mother's with him and his mother says
you know "Joe's been, it's kinda been odd,
"Joe's been carrying around this water bottle
"with him everywhere for the past few months.
"He seems to just be drinking
"liters upon liters of water a day."
And when asked about it Joe acknowledges this,
he says "Yeah, I have been a little bit
"more thirsty than usual." and because of this, he says,
"You know, I've been going to bathroom,
"I've been needing to urinate all the time."
Now, let's contrast Joe to Bruce here.
Now, Bruce is very different than Joe.
Bruce is a 45 year old gentleman.
And he's come in to the doctor
for his annual physical and when he goes to the doctor
he says, "You know doc, I've been feeling pretty good.
"I mean, yeah, maybe I've packed on
"a few extra pounds around the waist,
"but in general I'm feeling pretty healthy."
Now, say both Joe over here and Bruce
are seeing the same family practice doctor.
You know for Joe, he says "Yeah, I am worried
"about this thirst and urination and the losing weight.
"I think we should probably check Joe's blood sugar."
And then similarly with Bruce, even though
he doesn't have any symptoms, the doctor recommends
that Bruce has some routine screening done
that would include checking his blood sugar.
And it turns out that both Joe and Bruce
have very high blood sugar.
They have something called hyperglycemia,
which stands for high blood sugar.
And they're both diagnosed with diabetes.
But how can such different situations with Joe and Bruce
be caused by the same disease?
Now, to answer this question, we first,
really need to understand what exactly, diabetes is.
Now the first thing I wanna mention
is that I've been referring to diabetes mellitus
and there are a couple different conditions
that have the word diabetes in them.
But generally when people refer to diabetes,
they're referring to the disease diabetes mellitus,
which is what we're gonna be talking about.
So diabetes mellitus is a group of disorders that are
characterized by an inability of the body
to regulate its blood sugar levels.
And you'll notice that I put glucose here in parenthesis
after sugar, because glucose is the main type of sugar
that the body uses.
And this disregulation results in high blood sugar,
or hyperglycemia.
So, to get a better idea of this, let me just bring in
a simple diagram here.
So this right here in pink,
imagine this is a blood vessel and in this blood vessel
there is blood going through.
And that blood has glucose.
Now, glucose is a sugar and it's the body's
preferred source of energy.
And we get glucose from the foods that we eat,
and then the glucose that we eat
is stored throughout the body,
but primarily in the liver here.
And to regulate the amount of sugar that is in our blood
we have two hormones.
The first hormone I'll have over here in orange is insulin.
And then the second hormone I'll have over here in blue
is glucagon.
And then down here in green is a cartoon
of some cells in the body
that are gonna need this glucose for energy.
When the glucose level in the blood is getting too high,
the pancreas releases this insulin.
And what the insulin does
is it stops the release of glucose
from the liver into the blood and then it also
has this glucose be taken up by the cells.
And so this decrease in the amount of glucose
being put into the blood from the liver
and then the increase amount of glucose
leaving the blood going into these cells
causes that blood sugar level to go down.
So insulin decreases blood sugar.
But if insulin were to just act on it's own,
the blood sugar would be always way too low,
so when that blood sugar starts getting to a lower level,
the pancreas then will release glucagon.
And what glucagon does is it causes the liver
to release that glucose into the blood,
all that glucose that's stored there.
And then it also causes the pancreas
to stop producing the insulin so that less glucose
is being taken out of the blood and put into cells.
And therefore then, the effect of this
by having the liver put glucose into the blood
and then preventing the glucose from leaving the blood,
glucagon results in an increased blood glucose level.
So now, in diabetes, this insulin here
is either not being produced
or it's not functioning properly.
So let's just cross it out.
It's not doing its job.
And what happens is that the effect of glucagon here
is amplified.
So you get this increase in blood glucose levels.
And then as I mentioned, insulin causes
glucose to exit the blood and go into the cells
so that the cells can use the glucose for energy.
But if it's not around, this doesn't happen.
So despite the blood sugar,
the blood glucose level is getting higher and higher,
that glucose isn't able to get into the cells.
And the body isn't able to use all of that energy.
So in a sense, despite the presence
of plenty of blood sugar and energy,
the cells are actually kind of starving.
And that's actually what can go on.
You can have this really high blood sugar level,
but the body in some senses thinks it's starving.
And this idea of kind of starvation
in the face of plenty of energy is a little bit confusing.
So let me just make an analogy here
to hopefully have it make more sense.
So it's very similar here.
Now imagine instead of this pink blood vessel,
imagine this is a water main.
Now, the purpose of that water main
is to bring water to these houses.
Now, imagine that one of these pipes
that went from the water main to the house gets clogged.
Now, despite plenty of water
being travelling down the street
and being right by the house,
the house actually isn't able to get any water.
And this is kind of like that same idea of,
despite all of the glucose being in the blood,
when you don't have insulin,
you can't get the glucose into the cells.
Just like if you have a clogged pipe that prevents water
from coming from the water main into a house.
So now let's go back to Joe and Bruce
and understand how you can have the same disease
that causes such different presentations
in different people.
Remember I said that diabetes mellitus
is a group of diseases.
They're not all the same disease.
So, depending on the underlining mechanism that's going on,
the disease can present in very ways.
So Joe over here on the left,
he is a very typical presentation of type 1 diabetes.
And I'm gonna just abbreviate diabetes,
DM, for diabetes mellitus.
And in type 1 diabetes,
Joe's body isn't producing any insulin.
And that results in that high blood sugar.
But over here with Bruce,
he has a different underlying mechanism.
His presentation is very characteristic
for something called type 2 diabetes.
And in type 2 diabetes, the body produces insulin,
but the receptors on the cells
are not as sensitive to insulin,
so insulin just doesn't function like it's normally able to.
And so it has a very different presentation.
Even though for both of them,
insulin is not working properly
and it results in hyperglycemia,
which is the characteristic finding in diabetes,
depending on the underlying mechanism,
whether or not you are not producing insulin
or whether the insulin just isn't working properly,
you still have hyperglycemia
but the presentations can be very different.