Cushing’s Disease

Cushing’s disease develops slowly and the early signs are not always noticed.

Cushing’s disease is one disease that is far more common in pets than it is in humans. While six in 100,000 people suffer from this condition, it is 200 times more common in dogs, with one in 1,000 dogs suffering from this deadly disease.

The Causes – Cushing’s disease is a slowly progressive disease caused by an excess of the hormone, cortisol, in the animal’s body. It is the most common hormone-related disease seen in dogs, but the disease is rare in other pet species.

Cortisol is a normal hormone produced by the adrenal gland, essential for normal body function. Unfortunately in some animals, the adrenal gland produces an excess of cortisol, resulting in Cushing’s disease.
In some cases, Cushing’s disease is caused by external influences, as in the long-term use of medications with steroids in them for the treatment of skin diseases.

Eighty-five percent of dogs affected by Cushing’s disease have pituitary-dependant hyperadrenocorticism. This form is due to over-stimulation of the adrenal gland by another gland called the pituitary gland, which is located just underneath the brain.  One of the pituitary gland’s functions is to control the adrenal gland. It does this by sending specific hormones to the adrenal gland and, in some dogs, the cells of the pituitary gland multiply and excrete too much of these hormones, thus, in turn, overstimulating the adrenal gland to produce too much cortisol.

A further fifteen percent of dogs develop the disease from tumors in the pituitary or adrenal glands where these cells pump out excessive amounts of cortisol.

Genetics may cause the spontaneous type, since it appears mostly in certain breeds, such as Poodles, Daschunds, Boxers, Boston Terriers and Beagles. Cushing’s disease typically occurs in middle-aged to older dogs.

One of the obvious signs of Cushing’s disease are skin disorders that include the visible signs of rashes, flaky dandruff, hair loss and skin lumps. It can also cause an accumulation mineral crystals that cause skin deterioration in more severe cases.

The Effects – symptoms include:

  • increased thirst, urination & appetite
  • reduced activity, lethargic, weight gain
  • excessive panting, does not tolerate heat well
  • thin or fragile skin, hair loss
  • recurrent skin infections
  • enlargement of abdomen, resulting in a ‘pot-bellied’ appearance
  • Behavioural changes – dogs become less friendly towards their owners and often don’t sleep well

Fatigue and weakness can lead to loss of muscle coordination in the latter phase of the disease. It can also result in heart and skeletal problems and diseases of the nervous system.

If your veterinarian suspects your dog has Cushing’s disease, he or she will confirm the diagnosis with a variety of tests including urine and blood analyses.

The Treatments – while surgery is often used for pituitary tumours that cause Cushing’s disease in humans, surgery is not often conducted for this form of the disease in dogs because of the complexity of the operation. Instead, medications are the usual form of treatment but radiation therapy is also employed in some cases.

Most dogs with Cushing’s disease are middle-aged or elderly and owners sometimes ask if it is worth treating them. Once an animal with Cushing’s disease is stabilized on treatment they will usually live a normal life (simply taking their tablets on a regular basis).

The outcome for dogs with pituitary-dependent Cushing’s disease with treatment is very good. Some signs will disappear quickly and others more gradually. Appetite and water consumption usually return to normal in a few weeks; whereas full return of the fur may take several months. Without treatment the complications can be significant and will seriously affect the quality of your pet’s life.