Diabetes: the
definition
I can’t tell you all about a
disease without defining it first, and now is a good time to do that. In medicine we are nothing without our
objective criteria, classifications, and rating scales, so here’s the scoop for
diagnosing diabetes:
·
Fasting blood glucose greater than 126 mg/dl
o Normal
would be under 110 mg/dl
·
Two hour glucose tolerance test greater than 200
mg/dl
o This
is a test where the doctor gives you a standard amount of glucose to take,
makes you wait two hours, and sees if your pancreas can get it together to
secrete enough insulin to cause much of that glucose to “disappear” from the
blood into cells.
·
Non-fasting (random, anytime of the day) blood
glucose reading of over 200 mg/dl in the presence of symptoms of diabetes.
o Symptoms
of diabetes include increased thirst (polydipsia), increased urination
(polyuria), fatigue, and possibly weight loss.
o In
Type 2 diabetes, symptoms usually come on more slowly than in Type 1, and a
patient may present with some of the complications like changes in vision, more
infections, or nerve problems.
·
Hemoglobin A1c over 6.5%
o This
is my favorite lab test of all time: Hemoglobin
A1C (HbA1c) is a variant of hemoglobin (a protein found in red blood cells
that carries oxygen) that looks different than normal hemoglobin because it has
been “glycosylated.” Basically,
all the extra glucose in the blood
stream is sticky and attaches to hemoglobin molecules.
o The
thing about this test is that it’s a predictor of the average blood sugar over
the past 3 months. That’s the
average life span of a red blood cell, and once they get stuck with the sugary
goo, it doesn’t come off. So
basically this means that doctors know when diabetics say they are controlling
their blood sugar, but really are not.
Let’s say someone fits this
criteria and is diagnosed a diabetic.
Great, now what? There are
several treatment options that we’ll get to, but first, I think we need to take
a look at what diabetes does to the whole body. Hopefully I’ll make complying with those treatment options
seem like a really good idea.
The “side effects” of
diabetes
When
I say that diabetes takes a big toll on the entire body, I really mean the entire body. There are literally so many complications that I would bore
the pants right off you if I outlined them all. So let’s just talk big picture: high blood sugar that is uncontrolled will damage your big
blood vessels and your small blood vessels (fancy terms: macrovascular and
microvascular complications).
Big blood vessel
complications:
Diabetics undergo accelerated
atherosclerosis (you know, fat plugging up big important vessels, like the ones
carrying oxygen to your heart muscle, ie the coronary vessels). As a matter of fact, diabetics are
considered to be as high risk for heart attacks and strokes as someone who has already
had a heart attack or stoke.
We’re not super sure why atherosclerosis happens faster in diabetics,
but it might have something to do with the excess glucose attaching to the
walls of vessels, making platelets more likely to stick there and form a big
clot. The most common cause of
death of a diabetic patient is coronary artery disease (heart disease=big risk
for heart attacks). Other major
heart and stroke risk factors are high blood pressure, high lipids (LDL,
triglycerides, etc), smoking, and obesity. Unfortunately, most diabetics meet criteria for at least one
of these other risk factors too (remember the metabolic syndrome?). Decreasing some of these other risk
factors decreases the risk of heart attack and stroke in diabetics, but that
risk is still much higher than someone without the disease.
In addition to the big blood
vessels of the heart and brain being affected, the blood vessels that serve the
legs and arms are affected by diabetes and are prone to earlier “clogging” by
atherosclerosis, called peripheral vascular disease. This can cause all kinds of problems, including pain during
activity because the muscles can’t get enough blood and increased risk of sores
that don’t heal, leading to ulcers and infection. As a matter of fact, patients with nonhealing ulcers
sometimes need amputation of the affected limbs to spare the rest of the body
from spreading infection.
Diabetics account for almost 70% of all the non-traumatic amputations
performed in this country!!
Small blood vessel
complications
Long
term uncontrolled blood sugar does a lot of damage to the very small blood
vessels that provide nutrients to important “end organs”, like the eyes,
kidneys, and even nerves. We’ll
talk about each of these individually.
The
eyes: Oh, the poor eyes. High
blood glucose causes problems in two main ways. Firstly (and probably the first
to be noticed by the patient), fluctuations in glucose levels can cause the
cornea of the eye to become distorted in shape as glucose gets trapped and
water follows behind (swelling!).
This results in rapid changes in vision prescription needs, as light
travels differently through the different thicknesses of the cornea. Patients will often report to their eye
doctor several times within a year, complaining that their eyeglass
prescription isn’t working again!
The second way that diabetes does damage to the eyes is through
“diabetic retinopathy,” a fancy medical term for the changes that take place to
the retina, which is the nerve layer of the back of the eye that responds to
light and transmit the information to the brain. When the small blood vessels that serve the eye become
damaged, they can bleed onto the retina, causing small hemorrhages, or even be
cut off completely, creating areas of ischemia (decreased blood flow). As a result of the decrease in blood
flow, the eye tries to make more blood vessels to keep the nerve cells of the
retina alive in a process called “neovascularization”. These new vessels aren’t as good as the
original ones that were all clotted up with sugar though. In fact, they are weaker and can cause
retinal detachment, which is an emergency that can end in blindness!
The kidneys: Full disclosure: the kidneys are my
least favorite organs, mostly because they are the true workhorses of the body
and are incredibly complicated (and thus, very hard to understand as a medical
student). You would not believe
all the important bodily processes your kidneys take care of, and
unfortunately, they are very prone to damage in the diabetic state. Due to the high glucose load that comes
screaming through the kidneys every minute of every day, the microscopic
structure of the kidneys themselves change and eventually they start spilling
protein into urine, something they are never, ever supposed to do. This leads to swelling of the legs or
even the whole body, but more than that, it indicates that since the structure
of the little kidney cells are all changed, the whole kidneys themselves are
headed toward failure. It’s a very
serious thing when kidneys fail, making patients undergo dialysis for several hours
a week just to keep up with the blood-cleaning process the kidneys should be
performing. After needing regular
dialysis, life expectancy decreases significantly. It’s very, very bad to make the kidneys sick.
The
nerves: Diabetic neuropathy is a common complication, affecting as many as
70% of diabetics. Nerves of all
kinds can be damaged by diabetes, again through a variety of mechanisms, but
the idea is the same as for the other organs we’ve talked about; high blood
glucose levels damages blood vessels that keep those nerves alive and can
damage the nerves themselves.
There are tons of ways diabetic neuropathy can present, and a patient
may have a combination of these symptoms.
If the peripheral nerves (ones in your arms and legs) are affected,
there could be a sensation of burning, or “pins and needles”, or even a loss of
sensation completely, making it very hard for patients to tell when they have a
sore on their feet (the starting point for those non-healing ulcers that can
lead to amputations we’ve talked about).
The nerves that serve the internal organs and blood vessels can be
affected to, and this is called “autonomic neuropathy.” These symptoms are particularly
bothersome and can include any of the following: indigestion, nausea, vomiting,
diarrhea, constipation, difficulty urinating, and even dizziness or fainting on
standing. Men also experience a
high incidence of impotence due to damage to the nerves that control
erection. Do I have your attention
now?
End of part two
So
now we know how diabetes is diagnosed and the long-term effects it has on
organs like the brain, heart, blood vessels, eyes, kidneys and nerves. Next time we’ll talk about how doctors
decide who gets tested and start talking about treatment options. Most importantly, we’ll figure out how
a person can fend off diabetes completely because to me, prevention is the best
medicine!
No comments:
Post a Comment