The disease diabetes mellitus, also called sugar diabetes, results from a deficiency of—or decreased response to—insulin. The pancreas produces insulin, which helps body tissues process glucose (sugar). Without insulin or with a decreased response to insulin, blood glucose levels rise, resulting in hyperglycemia, while the body tissues remain starved for glucose. The elevated blood glucose eventually passes into the urine, creating a condition called glycosuria. As the disease progresses, metabolism changes cause ketosis, a condition in which chemicals called ketones accumulate in the blood and body tissues.
There are two types of diabetics. In Type I or insulin-dependent diabetics, the pancreas doesn't produce enough insulin, requiring an outside source. Nearly all diabetic dogs are Type I diabetics. Type II or noninsulin-dependent diabetics don't require an outside source of insulin. The pancreas produces insulin, but it doesn't produce enough, and the insulin is released slowly. To compound the problem, the tissues don't respond normally to the hormone.
Risk factors and detection
Diabetes mellitus affects dogs of any age, but it's most common in middle-aged to older female dogs. Obesity increases the risk of diabetes mellitus. Genetics also play a role, and some dog breeds, including golden retrievers, poodles, keeshonds, pulis, Cairn terriers, miniature pinschers, miniature schnauzers, dachshunds, and beagles, are predisposed to diabetes mellitus.
Any factors that interfere with insulin production or action increase the risk of diabetes mellitus. Some examples: female estrus (heat) and pregnancy hormones, glucocorticoids and certain hormones (megestrol acetate and progesterone), and other diseases, such as Cushing's syndrome and acromegaly. Diseases that destroy pancreatic cells, such as pancreatitis and viral infections, also cause diabetes mellitus.
Signs of diabetes mellitus include:
- increased thirst
- increased urination
- increased appetite
- weight loss
- blindness (cataract formation in dogs)
- a change in stance
As the disease becomes more advanced, you might notice:
- decreased appetite
- vomiting
- lethargy
- dehydration.
These last four signs occur as ketones accumulate in the blood and tissues—a condition that can be life-threatening. If you notice these signs in your dog, see your veterinarian immediately. Your doctor will perform a complete physical examination and use blood and urine tests to diagnose diabetes mellitus and identify any other diseases.
Prevention and treatment
A diet and exercise program to head off obesity and pancreatitis will help prevent diabetes mellitus. Spaying females also decreases their risk. Avoiding unnecessary use of corticosteroids, progesterone, and megestrol acetate minimizes these contributing factors.
Treatment for diabetes mellitus often includes several components. The first step: stabilizing the diabetic dog if ketones have accumulated in the blood and tissues. If your dog is ketotic, he will need hospitalization and intravenous fluids to correct dehydration and stabilize his condition.
The next step: regulating blood glucose levels with insulin.
Insulin injections are the most common and successful treatment for insulin-dependent diabetic pets. Dogs may need injections once or twice a day, depending on the insulin used and the dog's response. If the veterinarian diagnoses diabetes in your dog, he or she will conduct a series of blood glucose tests to determine how long the effects of insulin will last, how well insulin lowers your dog's blood glucose level, and when the highest and lowest blood glucose levels occur. By charting this information as a blood glucose curve, the veterinarian can tailor your pet's insulin therapy. Periodic follow-up visits to chart new blood glucose curves help your veterinarian monitor the therapy's effectiveness. Your veterinarian may ask you to monitor the glucose and ketone levels in your dog's urine at home with a simple dipstick test. If ketones appear in the urine, take your dog to the veterinarian immediately.
Diet plays an important part in regulating diabetes, and your veterinarian can recommend a specific food. But in general, if your dog isn't overweight, offer a diet you know he will eat, and feed him a set amount to keep the calories consistent. For overweight dogs, gradual weight loss over a few months will help regulate blood glucose levels. Ask your veterinarian to recommend a food that's low in fat and high in complex carbohydrates and fiber.
Consistent exercise helps prevent obesity, encourages weight loss in obese dogs, helps regulate blood glucose levels, and reduces the need for insulin. If you know your pet's exercise level will change significantly (during hunting season, for example), talk to your veterinarian. He or she can suggest diet and insulin adjustments to avoid low blood glucose levels during periods of increased exercise.
It's important to treat any other diseases in diabetic dogs. These pets have a compromised immune system and are more susceptible to infections. Antibiotics may help treat secondary infections, such as urinary tract infections, which are common in diabetic dogs.
The final treatment component is surgery. Spaying females as soon as their diabetes is regulated keeps estrus and pregnancy hormones from interfering with the body's insulin.
A possible complication of treating diabetes mellitus is hypoglycemia, an abnormally low blood glucose level. This may occur for several reasons, including not eating, participating in strenuous exercise, or accidentally receiving an overdose of insulin. If blood sugar falls too low, your dog may seem weak and uncoordinated, or he may experience a seizure. Always keep a high-sugar solution (Karo syrup, for example) on hand to feed your dog or to rub on his gums. If your dog is having a seizure, don't try to force him to swallow anything. Call your veterinarian or an emergency veterinary clinic immediately.
Prognosis
In dogs, diabetes mellitus is permanent and requires lifelong therapy with insulin. Complications may develop, such as cataracts, but diabetic dogs generally live a good life and have a normal life span.
