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Ask Dr. K: How diabetes types differ

DEAR READER: Type 1 and Type 2 diabetes are different diseases, but they share many things in common. Both types of diabetes are marked by elevated levels of blood glucose, or sugar. Type 2 diabetes, though, is much more common than Type 1 diabetes.

Type 2 diabetes also tends to begin in adulthood, although increasingly it is being seen in teenagers who are very obese. Type 1 diabetes tends to start in childhood, although it can start later in life.

The two types of diabetes can both lead to the same serious complications. Left untreated, or inadequately treated, either type can lead to heart attacks, strokes, kidney failure, amputation and blindness.

To understand diabetes — both Type 1 and Type 2 — it’s helpful to understand how your body metabolizes sugar. When you eat carbohydrates, your digestive system breaks them down into simple sugars, such as glucose. These simple sugars inside your gut get absorbed into your bloodstream. Then the sugar travels to your cells, providing nourishment and energy.

For sugar to give your cells energy, it has to get inside the cells. That’s where a hormone called insulin comes in. Insulin is a chemical made by the pancreas. When the pancreas “sees” sugar levels rising in your blood after you eat, it releases insulin into the blood. When insulin reaches your cells, it causes sugar to enter the cells.

When sugar enters your cells, it leaves the blood. As a result, blood sugar levels drop. On the other hand, if your pancreas can’t make enough insulin, or if your cells don’t respond normally to insulin, sugar can’t get into the cells and builds up in your blood.

In healthy people, blood glucose levels remain within a narrow range. This is important because certain organs, such as the brain and kidneys, depend on a consistent, steady supply of glucose.

The more common Type 2 diabetes results from a combination of abnormalities. First, your cells become less responsive to insulin. The pancreas rallies to compensate for this by pumping out more insulin. For a while, that keeps blood sugar levels normal. Eventually, the pancreas gets “pooped” and can’t keep up with the increased insulin demand. Blood sugar levels then rise, resulting in diabetes.

Treatments for Type 2 diabetes are drugs that make cells more responsive to insulin, drugs that encourage more insulin production by the pancreas, and insulin injections. Weight loss and regular exercise make cells more responsive to insulin.

The less common Type 1 diabetes is an autoimmune disease. The body’s immune system mistakes the insulin-producing cells of the pancreas as foreign and destroys them. This eventually leaves the body unable to produce insulin. To reverse symptoms, people with Type 1 diabetes must have daily injections of insulin. This replaces the insulin their bodies cannot produce.

A century ago, many people who developed either type of diabetes died prematurely. Let us be thankful that research has led to major improvements in treatment.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.

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