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Cushing's Syndrome

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  The adrenal glands of dogs with Cushing's disease (hyperadrenocortism) produce excessive amounts of cortisol, a hormone with potent anti-inflammatory and immuno-suppressive effects.

  There are three basic causes of Cushing's disease. These include pituitary-dependent hyperadrenocortism, adrenocortical cancer, and iatrogenic (medically induced) hyperadrenocorticism.

  About 85 percent of dogs with Cushing's have an overactive pituitary gland, which is a small pea sized gland in the brain producing an excessive secretion of a hormone ACTH. This in turn overstimulates the adrenal glands to produce cortisol in excess. The majority of the remaining cases result from adrenal tumors. About 50 percent of the adrenal tumors are benign. Iatrogenic hyperadrenocortism is due to prolonged administration or cortisone. These medications are used to treat a variety of illness in dogs.

  Cushing's disease is usually seen in middle aged to older dogs, and some breeds, such as Boston terriers, poodles, dachshunds, boxers, Scotties, and German shepherds, seem to be genetically predisposed to it. All breeds, however, can be affected.

  The signs of Cushing's include hair loss, excessive drinking and urination, exercise intolerance, pot-bellied abdomen, chronic infections and bilateral symmetrical hair loss. However, because these signs are not specific to Cushing's, veterinarians have to perform several laboratory tests to confirm the disease and then still have to determine its exact cause. Some dogs with Cushing's disease will also develop diabetes mellitus.

  Cushing's syndrome can be diagnosed effectively via blood tests. The tests used are the 'ACTH stimulation test' and the 'dexamethasone suppression test'. Both are relatively sensitive and specific. A skilled ultrasonographer may be able to detect enlarged adrenal glands via a scan, but this is seldom necessary with the availability of the blood tests.

  As stated before, most of patients suffer from the pituitary form of Cushing's. In such cases, medication can help dogs live out their years in healthy hormonal balance. Lysodren, the brand name for a drug called mitotane that destroys some of the cortisol-producing adrenal cells, is one of the drugs traditionally used to treat this disease. Fairly recently however a new drug has been licensed for treatment of Cushing's syndrome called trilostane. Trilostane (trade name Vetoryl) works by blocking the synthesis of cortisol. Not only is it more effective than Lysodren, it also has fewer adverse effects and has become the treatment of choice for dogs with Cushing's.

  Other medical options are available for the treatment of Cushing's disease. One alternative is ketoconazole, an antifungal drug that interrupts cortisol synthesis in the adrenal glands. This is effective in some dogs, but is also prohibitively expensive and has been phased out by the emergence of trilostane.

  Cushing's disease is a condition that cannot be cured, only managed. However, with prompt diagnosis, trilostane as treatment and regular health checks, a dog can live a long and happy life with this condition.

  © Televets 2007