December 24, 2006 by Maria-Elena Cloherty, DVM
Cushing’s disease, or hyperadrenocorticism is a disorder caused by excessive production of cortisol by the adrenal cortex. Too much adrenal hormone, in particular corticosteroids are produced. Another form of the disease, Iatrogenic, is caused by excessive amount of glucocorticoid steroid drugs administered to the patient. Approximately 85-90% of the naturally occurring cases of this disease are due to bliateral adrenocortical hyperplasia resulting from pituitary corticotroph tumors or hyperplasia with oversecretion of ACTH. The remaining 10-15% cortisol-secreting adrenocortical neoplasia is present, and a half of these are malignant changes.
Cortisol affects many body functions including the metabolism of protein, carbohydrate and fat, the immune response, and the inflammatory response. Because of this, there are a wide variety of signs which may be associated with this disorder. Hyperadrenocorticism is insidious in onset and progresses slowly. Cushing’s disease causes increased drinking, increased urination, increased appetite, panting, high blood pressure, hair loss – usually evenly distributed on both sides of the body, pendulous abdomen, thinning of the skin, calcified lumps in the skin, susceptibility to skin infections and diabetes, weakening of the heart and skeletal muscles, nervous system disease and other symptoms.
Diagnosis is based on typical clinical signs, laboratory abnormalities, and adrenal function tests which will help your veterinarian to determine if the disease is caused by abnormal pituitary stimulation of the adrenal glands, or by an adrenal tumour. Examples of drugs used to treat this disease are: L-Deprenyl (aka Anipryl, Mitotane (aka Lysodren), or Ketoconazole. If an adrenal tumour can be identified, it may be possible to remove it surgically, depending on the location and size of the tumour and whether it is benign or malignant.
This is one of the most common endocrine disorders in dogs, rarely found in cats and although a mode of inheritance has not been proposed, hyperadrenocorticism is more prevalent in the following breeds: poodle, dachshund, German shepherd, small terriers (Yorkshire, Dandie Dinmount). There also appears to be an increased incidence of the disorder in the boxer, Boston terrier, Labrador retriever, Australian shepherd, Maltese, and cocker spaniel. Females tend to have the adrenal tumors, but no sex predilection for pituitary based disease has been noted. This condition usually afflicts dogs of middle age, but pituitary dependent form has been seen in dogs less than one year.
If your pet shows signs and symptoms related to those above, it is important to have your pet seen by your local veterinarian so that they may properly diagnose and treat any possible illness or disease.
Resources & References
- From the Textbook of Veterinary Internal Medicine
- From the Encyclopedia of Canine Veterinary Medical Information
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