Cushing's disease can affect dogs of almost any age, but is most common in dogs over nine years old. Symptoms of Cushing's are often mistaken for normal signs of ageing, and this can cause a delay in treatment. The period of time a dog lives after a diagnosis of Cushing's disease depends on the form of the disease and on the treatment path taken.
Cushing's disease is a disease in which the adrenal glands overproduce cortisol; one of the hormonal substances necessary to sustain life. This hormone is known to help the body to respond to stress. Excessive production of this hormone may become life-threatening because it can affect a number of bodily functions. (For a list of functions affected by cortisol, see "References.")
Pituitary gland tumours cause Cushing's disease 85 per cent of the time. The tumour causes the pituitary gland to overproduce ACTH, stimulating the adrenal glands, which, in turn, overproduce cortisol. The tumour may be benign or malignant and is often very small. Iatrogenic Cushing's disease is caused by excessive doses of synthetic cortisones, often administered to dogs with allergies or other conditions needing steroid treatment. Finally, Cushing's can be the result of an adrenal gland tumour, which may be benign or malignant.
There are many symptoms that can signal the existence of Cushing's disease in your dog. He may experience excessive thirst or hunger. He may have increased urination and be unable to control his bladder. He may develop a bloated, sagging abdomen due to an increase of fat in the abdominal area. His skin may appear to be thin, like paper. He may be lethargic, showing no enthusiasm for activities, and he may pant excessively. (For more symptoms, see "References.")
Testing is necessary, as it can be difficult to diagnose Cushing's. A complete blood count, a urinalysis, an ACTH Stimulation Test and a Dexamethasone Suppression Test may be performed. An ultrasound exam may be necessary to check for an adrenal gland tumour.
To treat Iatrogenic Cushing's, your veterinarian will gradually reduce the amount of cortisone given for your dog's prior condition. Treatment may also be necessary to heal the adrenal glands that may have been affected. The Cushing's may be reversed, but the reason for treating her with cortisone injections in the first place may return. If an adrenal tumour is the cause of Cushing's, it must be removed by surgery. If the tumour is benign, and is successfully removed, the dog may return to a normal life. Treatment for a pituitary tumour may involve costly radiation, if the tumour is putting pressure on the brain, and medication to help manage the Cushing's disease. Tumours are not removed in these cases. Some medications can have serious side effects. (For information, see "References.")
Most cases of Cushing's occur in older dogs. If the disease is treated early, or if it can be reversed, life expectancy may be near normal. Some dogs can live productive lives for two to three years, and sometimes more, with successfully managed treatment of Cushing's disease that is due to a pituitary tumour.