How Cushing's Disease Affects Dogs
Because hyperadrenocorticism most often afflicts middle-aged to older dogs, the symptoms of the disease can fool owners who think that they are simply seeing the natural effects of aging in their canine companions. Cushing’s disease is caused by an excess of circulating cortisol hormone, which can result from functional tumors of the adrenal and/or pituitary glands. The disorder can also be caused by drugs administered for other ailments that stimulate excessive adrenal hormone production; this type of Cushing’s is called “iatrogenic.” However, if diagnosed properly and promptly, Cushing’s usually can be managed in a way that either eliminates it or mitigates its severity and greatly improves the dog’s quality of life. Since Cushing’s is largely treatable, and possibly curable, recognizing the clinical signs is critical to a pet’s prognosis.
Symptoms of Cushing's Disease
Cushing’s occurs most commonly in older animals and can mimic the so-called “normal” signs of aging. Owners of affected dogs may observe one or more of the following signs of the disease:
- Increased thirst and water intake (polydispsia)
- Increased urine output (polyuria)
- Inappropriate elimination (urinating in the house or other unusual places)
- Increased appetite and food intake (polyphasia; often ravenous)
- Weight gain; obesity
- Abdominal enlargement (pendulous, distended abdomen; pot-bellied appearance)
- Skin bruising
- Patchy, symmetrical hair loss (alopecia)
- Dry, dull hair coat
- Thin or fragile skin that tears easily
- Exercise intolerance
- Muscle atrophy
- Enlarged (hypertrophied) or atrophied external genitalia
- Lack of coordination (ataxia)
- Aimless wandering
- Poor wound healing
Cortisol increases appetite and thirst, so owners may notice that they are filling their dog’s food and water bowls much more often than usual, and in fact may report that their pet’s appetite is ravenous. Likewise, they often report abnormal hair loss that is symmetrical on both sides of their dog’s body, along with loss of muscle mass especially in the legs. Muscle atrophy and corresponding redistribution of weight often give dogs with this disease a “pot-bellied” look. They also commonly have poor wound healing. Dogs with hyperadrenocorticism are predisposed to developing other problems, including heart failure, diabetes mellitus, infections and high blood pressure. Typically, several of these signs appear at or around the same time. As the disease progresses, affected dogs’ signs typically worsen and increase in number. However, because Cushing’s is largely treatable, possibly curable and usually manageable, it is important for dog owners to become familiar with the signs of this disease.
Dogs at Increased Risk
Cushing’s disease appears most frequently in small dogs weighing less than 45 pounds. It is commonly seen in dogs over 6 years of age, with only a slight predisposition for female dogs, although dogs as young as 1 year have been diagnosed. Beagles, Boxers, Dachshunds, German Shepherds, Labrador Retrievers, Poodles and some breeds of Terriers (especially Boston Terriers) seem to be overrepresented.