Insulin Key to Diabetes, but Not Full Cure

by Food and Drug Administration (FDA)

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.

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