Cushing's Disease in Dogs: An Overview
Dog Breeds
Cushing’s disease in dogs is synonymous with hyperadrenocorticism and is the most common endocrine disorder in aging domestic dogs.
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Definition of Cushing’s Disease
Cushing’s disease in dogs is synonymous with hyperadrenocorticism and is the most common endocrine disorder in aging domestic dogs. It gets its familiar name from Dr. Harvey Cushing, who first described the disease in humans with pituitary gland tumors. There are several forms of the syndrome commonly referred to as canine Cushing’s disease: pituitary-based, adrenal-based and iatrogenic. All forms are chronic and slowly progressive. They cause the same clinical signs, and each requires treatment. The syndrome results from long-term exposure to abnormally high levels of steroid hormones.
Causes of Cushing’s Disease in Dogs
Cushing’s disease is caused by an excess of freely circulating corticosteroid hormones, which are produced by the adrenal glands. The adrenal glands are tiny, paired structures located in the abdomen above each kidney. The outer layer of these glands, called the adrenal cortex, produces corticosteroid hormones, which in turn are responsible for regulating electrolyte concentration, managing inflammatory reactions and suppressing the immune system, among other things. Production and release of steroid hormones are regulated by the pituitary gland, which is located in the brain. The pituitary gland produces adrenocorticotropic hormone (ACTH), which when released stimulates production of steroids by the adrenal glands.
The accurate term for Cushing’s disease is hyperadrenocorticism. It is most commonly caused by excess production and secretion of adrenocorticotropic hormone (ACTH) by the pituitary gland, due to either functional pituitary tumors or excess release of corticotrophin-releasing factor (CRF) by the hypothalamus. Cushing’s can also be caused by functional tumors of the adrenal gland, which promote excessive secretion of corticosteroids even without stimulation by pituitary ACTH. Finally, Cushing’s can be caused by excessive or prolonged use of steroid medications that stimulate or simulate excessive adrenal hormone production. This is called iatrogenic Cushing’s.
Prevention of Canine Cushing’s Disease
Unfortunately, other than managing the medical use of corticosteroids, there is no way to prevent hyperadrenocorticism in dogs. Functional tumors of the pituitary and/or adrenal glands occur for unknown reasons, and until the cause of those tumors is discovered, prevention of Cushing’s disease is not realistic.
Special Notes
Hyperadrenocorticism is a chronically progressive disease that can cause severe and eventually debilitating signs in domestic dogs. Fortunately, several medical protocols are available to help manage this disease.
Symptoms and Types