Cushing's disease in dogs
Cushing’s disease is one of the most common hormone disorders affecting dogs. At normal levels, the hormone cortisol helps the body to respond to stress and regulates the immune system. It is produced by a pair of small glands that sit next to the kidneys. Cushing's disease (also known as hyper-adreno-corticism) is caused by excess production of cortisol by the adrenal glands. It is typically seen in middle to older aged animals.
Symptoms of Cushing’s disease
The clinical signs of Cushing’s disease are quite characteristic. They include:
- Increased drinking
- Increased urination
- Increased appetite
- Loss of energy
- Poor hair coat
- Pot-bellied appearance
- Skin changes (dark pigmentation, thinning, bruising)
- Problems with skin wounds healing
Causes of Cushing’s disease
Cushing’s disease is caused when the dog’s own body produces too much cortisol. There are three reasons that overproduction of cortisol occurs:
- A tumour in the pituitary gland in the brain: the tumour is usually benign. It is a common cause of Cushing’s disease. This tumour leads to overproduction of the hormone that stimulates the adrenal glands (ACTH). Therefore, the adrenal glands produce too much cortisol.
- A tumour in an adrenal gland: this tumour is sometimes benign but can be malignant. Again, this tumour leads directly to overproduction of cortisol.
- Iatrogenic Cushing’s disease: at any age, a dog taking long-term or high levels of corticosteroid medication, usually for treatment of another disease, can develop signs of Cushing’s disease. Once the medication is slowly reduced and/or stopped, the signs of Cushing's disease should fully resolve.
Your vet may suspect Cushing’s disease from the clinical examination. It is not possible to diagnose the disease by one test alone, therefore, to confirm the diagnosis, a set of tests is usually needed. Blood and urine tests are the most common starting place, followed by hormone testing. Further investigations, such as an ultrasound scan, may provide further information and guide treatment.
Can Cushing's disease be prevented?
For Iatrogenic Cushing’s disease, your vet will indicate the lowest practical dose of corticosteroid medication for your pet. Or, your dog will be slowly weaned off the corticosteroid treatment completely. The signs should then fully resolve. Unfortunately, it is not possible to prevent the forms of the disease caused by a tumour. However, the treatment options are discussed in the next section.
Treatment of Cushing’s disease
- Pituitary gland tumour: lifelong drug treatments are used to stop the pituitary gland in the brain producing too much ACTH. This in turn will stop the adrenal glands producing excess levels of cortisol. The medication typically prescribed is called trilostane (Vetoryl).
- Adrenal gland tumour: either the tumour can be surgically removed, or, the tumour can be managed with medication. Diagnostic imaging will be used to see if the tumour has spread to other parts of the body. The treatment options will depend on the case. Your veterinarian will be able to discuss these options with you.
- Iatrogenic Cushing’s disease: your veterinarian will review the medication that your dog is receiving. They will advise you about how to reduce or stop the corticosteroid medication safely. It must not be stopped suddenly, as this can cause a life-threatening condition known as an Addisonian crisis. Supportive medical treatment is provided, as required.
Your veterinarian will schedule regular follow-up appointments for check-ups and blood tests, to monitor your dog’s progress. Although medical treatment cannot cure Cushing’s disease, it provides very effective control. Further information is available here.
When to see your physical veterinarian
- If you notice any of the signs listed above, then you should seek veterinary advice.
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