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CUSHING'S DISEASE

This a condition seen mainly in dogs.

It is brought on by excessive amounts of cortisone circulating around the body.

Symptoms

Dogs with Cushing's disease can show a wide variety of symptoms such as:

  • Excessive drinking
  • Excessive hunger
  • Pot bellied
  • Chronic skin problems
  • Hair loss (alopecia) along the abdomen and chest

Causes

  1. Excess amounts of cortisone therapy e.g. in long running skin problems
  2. Malignant tumour of the adrenal glands
    Tumours of the adrenal glands can force them to make excessive cortisone.
  3. Benign tumour of the pituitary gland in the base of the brain.
    This is the master gland of the body and this particular tumour makes chemicals which tell the adrenal glands to make excessive amounts of cortisone.

Prognosis

Left untreated, complications can occur e.g. diabetes, poor wound healing, infections, poor skin, pot bellied, fatty liver.

Dogs with pituitary gland tumours can go on to live comfortably for some time until the tumour gets too big and starts to place pressure on adjacent parts of the brain.

At this stage, we might see symptoms such as blindness and other hormone imbalances.

Unfortunately, adrenal gland tumours are often malignant and can spread to other parts of the body. They often respond to therapy with Lysodren (see below) but require regular check-ups to rule out complications.

Diagnosis

Suspected cases have blood tests done to try and find out where the excess cortisone is coming from.

Treatment – New Hope!

Cushing’s disease is treatable but treatment involves dedication of owners to follow guidelines recommended by their veterinarian.

Treatment will vary depending on the source of the tumour. A high percentage of Cushing’s disease is pituitary related. Treatment involves the use of a drug called Mitotane which directly affects the pituitary gland. More recently, a new drug called Trilostane is being used as a first line choice of treatment. Trilostane is an enzyme inhibitor which reduces the concentration of cortisol in the body. The advantage of this drug is that it does not directly affect the pituitary gland which is a vital gland for hormone regulation in the body. However, research has shown that dogs that have all ready started on mitotane should not make the switch to Trilostane.

Trilostane is showing promise in the treatment of other hormonal diseases such as alopecia.

Trilostane is also the treatment of choice if there is a confirmed diagnosis of an adrenal tumour. The other treatment sometimes advocated is removal of the adrenal glands.

With the use of either Trilostane or Mitotane, owners must comply with the dosage regime of these drugs and follow the guidelines of their veterinarian. Monitoring of treatment success involves a blood test called an ACTH stimulation test. This involves taking blood to check cortisol levels to see if they have dropped to an ideal level. Testing is done regularly after one week then at 1, 3, 6 months post treatment.

Sometimes, cortisol levels may drop too low and owners need to watch for symptoms of this – these include lethargy and a low heart rate. If an owner is at all suspicious of such symptoms, they should take their pet to their veterinarian for blood tests If the cortisol levels drop too low, supplementation of cortisol tablets is given at a very low dose.