Insulin Key to Diabetes But Not Full Cure
by Judith Randal

On July 30, 1921, Frederick Grant Banting, a research physician at the         
University of Toronto, and Charles Herbert Best, a medical student there,      
succeeded in isolating insulin from the pancreas of a dog. Within about a      
year, injections of the hormone became the first effective therapy for         
diabetes and scientists began to think the disease was conquered. But it       
didn't turn out that way, even though insulin has been an important treatment  
for diabetes ever since.

People who have diabetes mellitus (the full medical term for diabetes) are     
more than ordinarily vulnerable to many kinds of infections and to             
deterioration of their kidneys, hearts, blood vessels, nerves, and vision.     
According to the National Institutes of Health, more than 250,000 Americans a  
year die from the complications of this illness, largely because it doubles    
their chances of having heart attacks and strokes.

Diabetes is, besides, the nation's leading cause of kidney failure and adult   
blindness. And, because of the damage it can do to the blood vessels and       
nerves of the lower limbs, only accidents necessitate more amputations of the  
toes, feet and legs. Considering that an estimated 13 million to 15 million    
Americans--more than 1 in 20, evenly divided between the sexes--have           
diabetes, it is hardly surprising that it costs the nation $20.4 billion a     
year in time lost from work, Social Security disability payments, and          
health-care expenditures.

Despite this grim picture, there is reason for hope. It has become clear       
since the Banting-Best era that not everyone who has diabetes needs insulin    
and this, in turn, has improved diagnostic accuracy. Also, further advances    
have enabled doctors to better individualize treatment and patients to better  
take part in their own therapy.

Diabetes gets its name from the ancient Greek for siphon (a kind of tube)      
because early physicians noted that diabetics tend to be unusually thirsty     
and to urinate a lot: as if a tube quickly drained out everything they drank.  
The mellitus part of the term is from the Latin version of the ancient Greek   
for honey, used because doctors in centuries past diagnosed the disease by     
the sweet taste of the patient's urine. More fundamentally, diabetes impairs   
the body's ability to burn the fuel it gets from food for energy.

That fuel is glucose, a simple sugar the body makes by digesting starches and  
more complex sugars. It is carried to the body's cells by the blood. But the   
cells need insulin, which is made by the pancreas (a gland just behind the     
stomach) to put the glucose to work. Without it, they are starved for          
sugar--and thus are energy-deprived in the midst of plenty--because the        
glucose piles up in the blood and is removed by the kidneys, which dump it     
into the urine where it is excreted as waste.

This sometimes happens because the cells of the pancreas that make             
insulin--the beta cells--are mostly or entirely destroyed. Then the patient    
needs ongoing insulin treatment to survive and so is said to have              
insulin-dependent diabetes mellitus (IDDM). Another name for IDDM is type 1    
diabetes. Because it usually starts in childhood or adolescence, IDDM used to  
be called juvenile-onset diabetes, but that term has been dropped because it   
is now known that it can begin at any age.

Fewer than 10 percent of the Americans who have diabetes have IDDM. The rest   
have type 2 or non-insulin-dependent diabetes mellitus (NIDDM). In this form   
of the disease, the person's beta cells do make insulin and may, in fact,      
make too much. Here the problem is that the patient's tissues aren't           
sensitive enough to the hormone and so use it inefficiently.

NIDDM was once also called adult-onset or maturity-onset diabetes because it   
is largely a disease of people over 40 and the chance of getting it rises      
with age. However, doctors no longer use those terms because it, too, can      
strike at any age. Some NIDDM patients require insulin, but many do not.

Although both types of diabetes are popularly called "sugar diabetes," they    
are not caused by eating too many sweets. High sugar levels in the blood and   
urine are a result of these illnesses; their exact causes are unknown. What    
is clear is that NIDDM runs in families far more often than IDDM does and      
that--unlike IDDM, which cannot be prevented--it can frequently be avoided by  
staying in shape.

"At least 80 percent of those who get type 2 diabetes weigh 20 percent or      
more than they should and usually have for many years," says John L.           
Guerigian, M.D., of FDA's division of metabolism and endocrine drug products   
and executive secretary of the advisory panel to the agency on diabetes        
drugs. "Particularly if someone in your family became diabetic as an adult--a  
parent, brother or sister, for example--you can do yourself a favor by not     
putting on too many pounds and keeping fit."

Symptoms of IDDM typically appear abruptly and include excessive, frequent     
urination, insatiable hunger, and unquenchable thirst. Otherwise unexplained   
weight loss is also common, as are blurred vision (or other vision changes),   
nausea and vomiting, weakness, drowsiness, and extreme fatigue.

But the most immediately life-threatening aspect of type 1 diabetes is the     
formation of poisonous acids called ketone bodies. Like glucose, they          
accumulate in the blood and spill into the urine. Before the advent of         
insulin, the consequent ketoacidosis (acid buildup) was irreversible, causing  
most people who got IDDM to die within months.

Symptoms of NIDDM may include any or all those of IDDM, but are often          
overlooked because they tend to come on gradually and be less pronounced.      
Instead of urgently having to urinate around the clock, for example, people    
with type 2 diabetes may have to use the toilet frequently only at night.

Other symptoms that may signal the presence of type 2 disease are tingling or  
numbness in the lower legs, feet or hands, skin or genital itching and gum,    
skin or bladder infections that recur and are slow to clear up. Again, many    
people fail to connect them with possible diabetes.

Indeed, about half those who have NIDDM---some 6.5 million American            
adults--don't know it. Their ignorance is, at best, temporary bliss. While     
life-threatening ketone bodies are uncharacteristic of type 2 diabetes, it     
is, nonetheless, a serious disease. If neglected, its long-term risks of       
disabling and even fatal complications substantially increase.

Measuring glucose levels in samples of the patient's blood is key to the       
diagnosis of both types of diabetes. This is first done early in the morning   
on an empty stomach. For further information, the blood test is repeated,      
usually on another day, before the patient has drunk a liquid containing a     
known amount of glucose and at intervals afterwards.

"Together with the results of these tests, the patient's age and weight often  
pretty much tell us which type of diabetes it is," says Douglas A. Greene,     
M.D., of the University of Michigan Medical Center, who heads FDA's advisory   
panel on diabetic drugs. "If someone is young rather than old and lean rather  
than fat, we suspect type 1 disease (IDDM) rather than type 2, whereas we      
suspect type 2 disease (NIDDM) if the patient is heavy and getting along in    
years."

Further laboratory tests can be used when the diagnosis is uncertain. For      
example, type 2 patients rarely form ketone bodies while type 1 patients very  
often do. Thus, blood tests for evidence of ketone body activity can help to   
determine which type of diabetes the patient has.

Treatment for either type seeks to do what the human body normally does        
naturally: maintain a proper balance between glucose and insulin. The guiding  
principle is that food makes the blood glucose level rise while insulin and    
exercise make it fall. The trick is to juggle the three factors to avoid both  
hyperglycemia, meaning a blood glucose level that is too high and              
hypoglycemia, meaning one that is too low.

Either problem can make the patient feel unwell and cause mental confusion,    
loss of consciousness, and even death if it becomes severe. For this reason,   
patients should wear bracelets identifying them as diabetic and in need of     
immediate medical attention if unable to summon it themselves. In addition,    
almost any degree of hyperglycemia is thought to add to the likelihood of the  
long-term complications that can afflict type 1 and type 2 diabetics alike.

Accordingly, many patients regularly track their blood glucose levels          
themselves so that they and their doctors can take steps to keep them within   
fairly normal limits and promptly correct the levels when they stray too far.  
(See "Improving Blood Glucose Monitoring for Diabetics" in the May 1990 FDA    
Consumer.)

Since there is no cure for either kind of diabetes, treatment is lifelong. It  
always includes dietary restrictions, which most patients are better able to   
follow if a nutritionist or registered dietitian helps them to build           
flexibility and variety into their meals and snacks. A diabetes educator       
(usually a nurse) who can tutor patients in self blood glucose monitoring,     
critically important foot care, and other coping skills can also be very       
helpful.

All diabetes patients should, besides, refrain from smoking and abstain from   
or at least go easy on alcohol. And, unless there are reasons why they should  
not exercise, they should do so regularly, being sure to check with their      
doctors about what sort of exercise will be beneficial and safe for them.      
Type 1 diabetics, in addition, must take insulin injections or wear a small    
battery-powered pump that infuses insulin into the body.

Because the vast majority of type 2 diabetics are heavier than they should     
be, weight loss alone is often prescribed first. Slimming in itself may        
normalize (or nearly so) blood glucose levels, even if the patient does not    
get down to his or her ideal weight. But the pounds should be lost for good.   
Subsequent attempts at weight loss are less likely to be as successful or to   
lower blood glucose levels as much.

When diet and exercise fail to sufficiently lower blood glucose levels in      
type 2 patients, the doctor may decide to add insulin, an oral sulfonylurea    
drug or both. However, no drug can replace diet and exercise; they are always  
essential.

Sulfonylurea drugs are used only for type 2 diabetes, mainly for patients      
whose diabetes is judged less severe. Insulin is the usual choice for          
advanced type 2 cases, and both drugs may be given if the illness is           
somewhere in between. (Patients on insulin alone often must take it several    
times a day; those who also take a sulfonylurea drug usually need insulin      
only once daily.)

These are, however, just rough rules of thumb. A patient's age, body build,    
lifestyle, preferences, how long he or she has had diabetes, and overall       
health may figure in the decision. In addition, experts disagree about         
whether patients are more likely to have heart attacks if treated with a       
sulfonylurea drug than if treated with just diet or diet and insulin.

Only one of the six sulfonylurea drugs sold in this country--tolbutamide       
(Orinase)--was used in the major scientific study that led to this             
controversy. But the other five are chemically very similar to it. FDA,        
therefore, requires the manufacturers of all sulfonylureas to include in the   
labeling and any promotional material for physicians a warning of this         
potential hazard.

The names of these other drugs are acetohexamide (Dymelor), chlorpropamide     
(Diabinese), glipizide (Glucotrol), glyburide (Diabeta and Micronase), and     
tolazamide (Tolinase). There are differences among them that can bear on       
which a doctor prescribes. For example, both tolbutamide and chlorpropamide    
can cause dizziness if combined with alcohol, a consideration for patients     
who drink.

It is not always clear whether insulin, oral medication, both, or just a more  
rigorous diet is best for a given type 2 patient. And some experts believe     
that a sulfonylurea should not be used with insulin. Patients may want to ask  
their doctors to explain all the options and the pros and cons of each.

Despite good treatment and control, both type 1 and type 2 patients tend to    
develop complications, especially as time goes on. Their impact can often be   
minimized or slowed by routine physician monitoring and by patients' promptly  
reporting even minor symptoms and changes in their well-being to the           
appropriate physician or other health-care professional.

Regular dental checkups are particularly important. So are periodic eye        
examinations by an ophthalmologist (physician eye specialist). Diabetics get   
cataracts and glaucoma more often than most people and also are prone to       
another potentially blinding disorder--diabetic retinopathy--that other        
people don't get. The sooner these disorders are detected, the greater are     
the chances of treatment's saving the patient's sight.

As Edward S. Horton, M.D., of the University of Vermont--a recent president    
of the American Diabetes Association--sums it up: "Diabetes can be a deadly    
disease. But with the help of modern medicine and their own efforts, many      
patients can lead long, active and relatively healthy lives."

Judith Randal is a freelance writer in Lovettsville, Va.

Types of Insulin

The more than 30 insulin formulations on the U.S. market are variations of     
several basic types, the most commonly used of which are:
- Purified Pork--pork pancreas-derived insulin that has undergone further      
purification
- Purified Beef--beef pancreas-derived insulin that has undergone further      
purification
- Recombinant DNA-origin (Human)--genetically engineered insulin made by a     
inserting the human gene for insulin production into a non-disease-producing   
laboratory strain of Escherichia coli bacteria or into yeast.
Formulations of all insulins also vary by how quickly they act and for how     
long. Some formulations contain a mix of insulins that vary on these scores    
as well. Also, some are packaged to be used with only one manufacturer's       
model or models of injection or portable pump devices.

Each type of insulin has specific benefits that the doctor takes into          
consideration before telling the patient which insulin to take.

When insulin was first marketed in this country in the 1920s, no prescription  
was required because many patients did not have telephones and lived far from  
a doctor. FDA has allowed insulin to remain on the market OTC because it's     
needed by a large number of people whose lives depend on it. However, some     
states require a prescription for insulin and the devices used to administer   
it.

Diabetes patients should use only the insulin formulation their doctor         
recommends and should not switch formulations without their doctor's           
approval.  

Resources


More information about diabetes is available from these sources:
American Diabetes Association
1660 Duke St.
Alexandria, VA 22314
(also has state and local chapters)

Juvenile Diabetes Research Foundation International
4332 Park Ave. South
New York, NY 10016
(1-800) 223-1138

American Heart Association
7320 Greenville Ave.
Dallas, TX 75231
(also has state and local chapters)

National Diabetes Information Clearinghouse
Box NDIC
Bethesda, MD 20892

National Institute of Diabetes and Digestive and Kidney Diseases
National Institutes of Health
Building 31, Room 9A04
Bethesda, MD 20892

National Eye Institute
National Institutes of Health
Building 31, Room 6A32
Bethesda, MD 20892

National Heart, Lung, and Blood Institute
National Institutes of Health
Building 31, Room 4A21
Bethesda, MD 20892

National Institute of Dental Research
National Institutes of Health
Building 31, Room 2C35
Bethesda, MD 20892

American Society of Diabetes Educators
500 North Michigan Ave.
Chicago, IL 60611
(1-800) 338-3633

American Dietetic Association
430 North Michigan Ave.
Chicago, IL 60606
(1-800) 366-1655