WHAT IS DIABETES MELLITUS?

Diabetes mellitus is a metabolic disease involving the body’s handling of sugar.  In order to understand Diabetes mellitus, it is important to have some understanding of the normal situation first.

The cells of the body require energy to conduct their assorted functions. They burn either fat or sugar to do this.  The sugar they use is called “glucose.”  Glucose can be manufactured by our bodies out of proteins or fats but largely we get our glucose from the food we eat.

Food is digested and glucose is absorbed and stored.  A hormone called “insulin” is responsible for the normal storage of glucose. When it is time to mobilize glucose resources, a hormone called “glucagon” is released to liberate sugar stores.  Both insulin and glucagon are made and stored in the pancreas.

In diabetes mellitus, there is either no insulin or not enough.  Sugar cannot be stored. With only glucagon to circulate, sugar is mobilized, fat stores are depleted, and muscle is broken down to liberate glucose.  In short, the body thinks it is starving and breaks itself down to desparately generate circulating sugar that it does not actually need.

Glucose is normally a valuable body resource and the kidney possesses a natural barrier to prevent the loss of glucose in urine. In diabetes mellitus, this barrier is overwhelmed and sugar is spilled into the urine. (The term “diabetes mellitus” literally means “sweet urine.”)  Sugar in the urine biochemically pulls water into the urine with it creating large volumes of very dilute urine.

The end result is the following constellation of classical symptoms:

• Excessive hunger
   
• Weight loss
   
• Excessive thirst
   
• Excessive urination

HOW DOES “TYPE I” AND “TYPE II” FIT IN?

Diabetes mellitus is a classical disease in humans and most of us have heard some of the terms used in its description. In humans, diabetes is broken down into two forms: Type I and Type II. These are also referred to as “juvenile onset” and “adult onset” or “insulin dependent” and “non-insulin dependent.”  The easiest way to think of these two types is the kind where the pancreas produces no insulin at all versus the kind where the pancreas produces some insulin but not enough.

These categories do not really fit well into animal models of diabetes mellitus. For all practical purposes, diabetes mellitus for pets is treated with insulin injections. It should be noted that in the cat, there is a possibility of treating with an oral hypoglycemic agent rather than insulin injections but this is still not the best method of treatment in the long run.

HOW DO PETS BECOME DIABETIC?

This is a complicated topic and there are many contributing factors to the development of diabetes mellitus.   Obesity is a factor, as is heredity.  Hormonal diseases such as Cushing's Disease (“hyperadrenocorticism”) commonly predisposes animals to diabetes mellitus; in fact, it would be surprising for a cat with Cushing’s Disease not to be diabetic. In dogs, pregnancy and estrus cycling can produce enough insulin resistance to lead to temporary diabetes. Inflammatory destruction of the pancreas, as in pancreatitis, can bring about temporary or permanent diabetes in dogs; however, in both cats and dogs, immune-mediated destruction of the pancreas is probably the most common cause. Some medications such as Progesterone derivatives (sometimes used to manage behavior problems) and Corticosteroids (prednisone, dexamethasone, and others) can lead to diabetes depending on how they are used.

HOW IS THE DIAGNOSIS REACHED?

A history of excessive water consumption, excessive hunger, and weight loss are a strong clue. From here, some basic blood and urine testing is performed to see if there is sugar in the urine and if the blood sugar level tests very high.

In some patients, the history is incomplete. Some owners really do not know if their pet is drinking excessively or has excessive hunger.  Because stress can elevate the sugar parameters on a blood test, it may be necessary to run an additional test to determine if the pet is diabetic. A test called a “fructosamine” level or a test of “glycated hemoglobin” can be run. These tests provide a sort of an average blood sugar level from the past couple of weeks.  If one of these tests is high, this would indicate that a high sugar level on the blood panel was not a fluke and that the pet is indeed diabetic.

ONCE IT HAS BEEN DETERMINED THAT THE PET IS DIABETIC, TREATMENT WITH INSULIN IS RECOMMENDED.