Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Diabetes Mellitus: A Disease of Humans and Pets Alike


Pet Column for the week of June 10, 2002


Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Jennifer Stone
Information Specialist

She was such a sweet kitty, and I hated to do it. She didn't like the shots and would always lead me on a merry chase each time I had to give her an injection. At the very least she was a healthy, well-managed diabetic, and that was what was important.

Diabetes mellitus can affect humans and animals alike. It can be a debilitating disease if untreated, and managing it can be a challenge. Once an effective treatment is established, however, pets can often live long, healthy, practically normal lives.

When most people think of diabetes, they think of diabetes mellitus. Dr. Rhonda Schulman, a veterinary specialist in internal medicine at the University of Illinois Veterinary Teaching Hospital in Urbana, says, "Diabetes mellitus is a common disease that is very easy to diagnose in both cats and dogs, but can be difficult to manage."

Diabetes Mellitus Type I is a condition in which not enough insulin is released by the pancreas so glucose cannot be utilized by cells for energy. Insulin acts as a transporter to carry glucose into cells. An insulin deficiency means the glucose stays in the blood instead of passing into the cells. This usually occurs when the beta cells (the cells in the pancreas that secrete insulin) have been destroyed. If enough glucose builds up in the blood, glucose will eventually start coming out in the urine, causing the animal to drink large amounts of water and to urinate excessively.

"There is also a Type II Diabetes Mellitus that occurs when the body becomes resistant to the effects of insulin and/or the beta cells of the pancreas are dysfunctional," says Dr. Schulman. "Obese patients are particularly susceptible to this type of diabetes."

Dogs and cats develop diabetes mellitus for many reasons. Dogs can get it because of immune-mediated disease in which the dog's own antibodies attack and kill the pancreatic beta cells. Cats often get the disease from the accumulation of a special kind of protein around the beta cells. Both dogs and cats can develop the disease because of inflammation of the pancreas (called pancreatitis), hereditary defects of the pancreatic beta cells, obesity, other illnesses, and infections. All dogs that get diabetes must be supplemented with insulin. For about a third of all cats with diabetes, the disease may be managed through other means, such as dietary changes.

Excessive urination and water consumption are probably the most well-known features that accompany all forms of the disease. Other signs of diabetes mellitus include a ravenous appetite and weight loss in spite of excessive food consumption. Because the cells of the body are not receiving nutrients, the animal is really in a state of starvation, so the brain sends signals to the animal's body to tell it that it is very hungry. In the meantime, the body begins to break down its own resources to survive (i.e.muscle and fat) and weight loss ensues.

Another problem associated with diabetes is cataracts, which can develop because hyperglycemia (excess glucose in the blood) can cause water to accumulate in the lens of the eye, causing swelling and disruption of the fibers of the lens. This process is irreversible and can lead to blindness within a matter of days in severe cases.

Diabetic patients are also predisposed to urinary infections because the excess glucose in the urine may cause bacteria to grow more readily.

The diagnosis is made through observing the signs of the disease, detecting excess glucose in the blood even when the animal has not eaten anything, and noting glucose in the urine. These lab results are easily obtained and can give a quick and definitive diagnosis.

"The goal of treatment of the diabetic patient is to reduce the clinical signs and to prevent any complications of the disease," says Dr. Schulman. "Sometimes successful treatment of diabetes can be as simple as feeding a high-fiber diet and controlling the cat's weight."

When insulin is required to control the diabetes, however, it can be difficult to determine the right amount of insulin to give. If too much is given, then animal can become hypoglycemic (too little glucose in the blood), which can have life-threatening effects. If too little is given, the diabetes will remain uncontrolled.
The only way to accurately determine the correct level of insulin is to feed the animal, give the insulin and then take blood samples every two hours until the level of glucose in the blood peaks and goes back down as the insulin has its effect. This is called a glucose curve. "This process can be frustrating and time consuming," says Dr. Schulman, "but it is really the only accurate way to tell if the insulin is working appropriately." She encourages owners to seek treatment because most animals with diabetes can still lead a happy life.

If you suspect that your pet may be diabetic or you have more questions regarding diabetes mellitus, please contact your local veterinarian.