Diabetes is a disease in which the blood level of glucose, a type of simple sugar, is too high. There are two types of diabetes, referred to as type 1 and type 2, depending on the process that that causes the high blood sugar. While insulin is used to treat both type 1 and type 2 at different stages of the disease, the decision to use insulin as opposed to oral medications at the initial diagnoses depends entirely on the diabetes type.
Type 1 Diabetes
Normally, the pancreas secretes a hormone called insulin in response to rising levels of glucose in the blood. Insulin signals muscle and fat cells to absorb glucose out of the blood, which lowers the blood levels and supplies these cells with the fuel they need to contract or store fat. In type 1 diabetes, the insulin secreting cells of the pancreas are destroyed by an autoimmune process that probably begins with a viral infection, notes "Harrison's Principles of Internal Medicine." Since there is no way of getting the damaged pancreas to secrete more insulin, type 1 diabetics always need external insulin to keep their blood sugar under control. The pancreatic destruction proceeds fairly rapidly, so by the time they are diagnosed, virtually every type 1 diabetic is started on insulin. Type 1 diabetes is usually first diagnosed in children or teenagers, and for this reason it was once called childhood diabetes.
Type 2 Diabetes
In type 2 diabetes, the pancreas secretes plenty of insulin, but the fat and muscle cells in the body become less sensitive to its signal to take in glucose, a condition known as insulin resistance. The causes of insulin resistance are complex and not entirely understood, but it is clear that genetics, obesity and inactivity are all involved in some way, notes "Greenspan's Basic and Clinical Endocrinology." Initially, the pancreas responds to insulin resistance by simply secreting more insulin, so blood glucose levels remain under control. As insulin resistance increases, however, the pancreas can no longer secrete enough insulin on its own to keep blood glucose under control, and the result is diabetes. Type 2 diabetes has usually been diagnosed almost exclusively in adults, so in the past it was known as adult-onset diabetes. In the later stages of the disease, the pancreas becomes exhausted and can no longer secrete any insulin at all; at this point, type 2 diabetics require insulin just like type 1 diabetics. In the early stages, when the disease is usually diagnosed, there are more medication options because the pancreas is still functioning. Oral medications for type 2 diabetes either decrease insulin resistance or get the pancreas to secrete more insulin.
Medication Choices for Type 2 Diabetes
In general, oral medications are the preferred approach for controlling blood sugar in a newly diagnosed type 2 diabetic. The pancreas continually adjusts its insulin output very precisely to the level of blood glucose, so it will always do a better job of keeping blood sugar at precisely the right level than an injection of insulin given in response to just one blood sugar reading. The only reason why insulin may be preferable to oral medication in a newly diagnosed diabetic is if there is uncertainty over the type. There is no easy way of testing which process -- type 1 or type 2 -- is responsible for the diabetes. Traditionally, the age at the time of diagnosis was used to determine the type, but this approach is now known to be flawed. In the early 1960s it became clear that there are some cases of type 1 diabetes, sometimes called type 1b in distinction with the more common type 1a, that are first diagnosed in adulthood, notes "Greenspan's Basic and Clinical Endocrinology." In addition, with the significant increases seen in the rates of severe childhood obesity since 1980, more and more cases of what is clearly type 2 diabetes have been diagnosed in children and teenagers, according to a 2002 article in the "Journal of Pediatric Endocrinology and Metabolism." If a doctor is uncertain about the type of a patient's newly diagnosed diabetes but suspects it may be type 1, he may choose to start the patient on insulin immediately to avoid the risk of additional episodes of dangerously high blood sugar that may occur if oral medication is tried and proves ineffective.
References
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper, et al. (eds.); 2005
- "Greenspan's Basic And Clinical Endocrinology"; DG Gardner and D Shobak (eds.); 2007
- "Journal of Pediatric Endocrinology and Metabolism"; Type 2 diabetes mellitus in children and youth: a new epidemic; FR Kaufman; May 2002
