Diabetes Mellitus in the Dog and Cat with Special Emphasis on Feline Diabetes

The vast majority of dogs have insulin-dependent (type 1) diabetes mellitus. In 90% of the cases the cause is linked to autoimmune destruction of the beta cells or pancreatitis. Secondary diabetes from chronic insulin resistance and subsequent beta cell burnout (e.g., with Cushing’s disease, acromegaly, and diestrus) accounts for approximately 10% of canine diabetics. In approximately 80-95% of cases, feline diabetes mellitus is similar to type 2 diabetes in humans. Both are characterized by an absolute or relative insulin deficiency coupled with insulin resistance. The other 5-20% of affected cats have other specific causes of their diabetes such as pancreatitis or pancreatic cancer, acromegaly, Cushing’s syndrome, or hyperthyroidism. The majority of diabetic cats are between 10 and 13 years and only 5-40% of diabetic cats with presumed type 2 diabetes can be controlled without insulin. Type 2 diabetes is the result of impaired insulin secretion and insulin action (decreased insulin sensitivity or insulin resistance). Diabetic cats are 6 times less sensitive to insulin than normal cats. As insulin sensitivity decreases more insulin is required to produce the same glucose lowering effect. Eventually this hyperinsulinemia cannot be sustained by the beta cells and overt diabetes develops.