Diabetes mellitus is the second most common endocrine disease diagnosed in cats. Diabetes in cats may actually have many different causes. However, the end result of all of these causes of diabetes is either a decrease in insulin secretion or a resistance in cells to the affects of insulin. Both decreased insulin secretion and increased insulin resistance lead to hyperglycemia, an increase in blood glucose, in the affected animal. This hyperglycemia is responsible for most of the symptoms seen in cats with diabetes mellitus.
Symptoms of Diabetes Mellitus in Cats
The most commonly seen symptoms in cats with diabetes are:
- increased appetite
- increased thirst
- excessive urination
- weight loss
Urinary tract infections are common complications seen with in cat with diabetes mellitus.
A flat-footed gait and/or stance is also commonly observed in diabetic cats. This abnormality is referred to as a neuropathy and is caused by a disruption of the myelin sheath which protects specific nerves, resulting in the inability of the nerve to properly transmit electrical impulses. The hind legs are involved more often than the front legs. The symptom may involve one limb or more than one limb.
Unlike dogs, diabetic cats do not normally suffer from diabetic cataracts.
Classification of Feline Diabetes
In people, diabetes mellitus is classified as Type 1 (insulin dependent) and Type 2 (non-insulin dependent). Type 1 diabetes is characterized by diseased beta cells in the pancreas which secrete insufficient amounts of insulin. Insulin in required to treat Type 1 diabetes due to the insulin deficiency. In Type 2 diabetes, some amount of insulin is still produced by beta cells and there are other factors, such as insulin resistance, which affect glucose metabolism. Therefore, Type 2 diabetes can often be treated through the use of dietary changes, oral hypoglycemic agents and weight loss (where necessary). Insulin is often not a necessary part of treatment of Type 2 diabetes in people.
Researchers have found that diabetes in cats sometimes mimics Type 2 diabetes in people, particularly in the early stages of disease. However, if the disease is left untreated, constantly elevated blood glucose levels cause the beta cells in the pancreas to over-work to produce adequate amounts of insulin. This eventually leads to death of the beta cells in the pancreas, essentially creating a insulin-dependent, or Type 1, diabetes.
Diagnosis and Treatment of the Diabetic Cat
Hyperglycemia (an elevated blood glucose level) is the hallmark lab abnormality seen with diabetes mellitus. However, many cats experience a stress hyperglycemia (an elevation in blood glucose in response to a stressful situation), which makes diagnosis of diabetes mellitus more challenging than simply finding a high blood glucose level. Often, additional blood tests, such as fructosamine, are required to accurately diagnose diabetes in a cat.
When diagnosed early in the course of diabetes, it is possible that some cats may respond to oral hypoglycemic agents along with a proper diet. However, many veterinarians now recommend the use of insulin and proper dietary modifications as an initial treatment of feline diabetes due to the fact that clinical remission is possible if hyperglycemia can be controlled early in the course of the disease. Research has indicated that this seems less likely to occur with the use of oral hypoglycemics than with the use of insulin.
Unfortunately, many cats are not diagnosed early in the course of diabetes and have become insulin dependent by the time the diagnosis is made. In this situation, insulin administration will be necessary to treat the cat.
Left untreated, feline diabetes can proceed to a life-threatening keto-acidotic state. At this point, hospitalization with insulin administration and supportive treatment will be necessary to save the cat's life.
Monitoring of diabetic cats will rely on owner observations of the cat's progress and will also likely involve periodic blood glucose curves, other blood testing and possibly urine testing.
Source: Diabetes Mellitus in Cats, Jacquie Rand & Rhett Marshall, Veterinary Clinics of North America Small Animal Practitioner, January, 2005 Pg. 211-224.
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