Canine diabetes mellitus is caused by the destruction of beta pancreatic cells, a specific type of cell within the canine pancreas which is responsible for secreting insulin. As a result of the destruction of these cells, diabetic dogs become insulin deficient. With insulin being the leading hormone responsible for regulating blood glucose levels, diabetic dogs become unable to metabolize their blood glucose properly, leading to an elevated blood glucose level, known as hyperglycemia.
Symptoms of Canine Diabetes Mellitus
The classic symptoms seen with diabetes mellitus in dogs are:
- polyuria, an increase in urine volume
- polydypsia, an increase in water consumption
- weight loss
- polyphagia, an increased appetite
Cataracts may also be seen in the eyes of diabetic dogs and are the result of a reaction in the lens of the eye to the influx of glucose within the lens.
In some cases of diabetes in dogs, a genetic predisposition to the disease may be present. Some breeds are more likely to develop diabetes than others. These breeds include:
- German Shepherds
- Schnauzers
- Beagles
- Poodles
Diabetic dogs are more likely to be females than males, though both genders can develop diabetes mellitus. The most common age of onset for canine diabetes mellitus is between six to nine years of age. However, Golden Retrievers and Keeshonds have been observed to develop diabetes mellitus at an earier age than other breeds and may develop a juvenile form of diabetes.
Classification of Diabetes Mellitus in Dogs
Diabetes mellitus in dogs is almost always classified as Type 1, or insulin-dependent diabetes. Unlike diabetes mellitus in cats and in some people, diabetes in dogs usually involves a relative insulin deficiency rather than tissue resistance to the effects of insulin. This relative insulin deficiency explains the fact that insulin therapy is almost always necessary to treat diabetes mellitus in dogs. Oral hypoglycemic agents, such as glipizide, require that the pet have at least partial ability to secrete insulin in order to work properly to decrease blood glucose levels. Most diabetic dogs have no remaining ability to secrete insulin and these oral hypoglycemic drugs are not effective.
Diagnosing Dogs with Diabetes Mellitus
Diabetic dogs always have elevated blood glucose levels, or hyperglycemia. Hyperglycemia is the hallmark characteristic of canine diabetes mellitus. The elevated blood glucose levels result in excessive amounts of glucose passing through the kidneys and being found in the urine, a condition known as glucosuria.
Another blood test which may be used to diagnose diabetes mellitus in dogs is the fructosamine level. Fructosamine is a glycolated protein test which provides an average blood glucose reading for the past 10-21 days. Fructosamine levels may be useful in differentiating a persistent hyperglycemia from a transient episode. Fructosamine levels are often combined with blood glucose curves to monitor the response to insulin therapy for diabetic dogs.
The classic diabetic dog is a middle-aged female dog who is constantly thirsty, is urinating frequently and is losing weight in spite of being hungry constantly. Though females are more often diagnosed with canine diabetes mellitus, male dogs may develop diabetes as well. In addition, some breeds (specifically Golden Retrievers and Keeshonds) may develop diabetes at an earlier age. Insulin is the treatment of choice for canine diabetes mellitus, together with proper dietary management.
Sources:
Feldman EC, Nelson RW: Diabetes mellitus. Canine and Feline Endocrinology and Reproduction, 2nd ed. Philadelphia, WB Saunders 1996 pp. 339-391.
Melendez L, Lorenz M: Canine Diabetes Mellitus. Western Veterinary Conference 2002.
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