What is Cushing’s Disease in dogs?

Cushing’s disease (or hyperadrenocorticism) occurs when the adrenal glands produce too much of the steroid cortisol that is often referred to as the stress hormone. This hormone is important for various functions including the immune system and for helping the body to deal with stressors. Its level is normally precisely controlled by signals from the brain.

Cushing’s disease is most common in middle-aged and older dogs, and certain breeds appear to be predisposed including Dachshunds, poodles and some terriers.

What causes Cushing’s Disease in dogs?

Cortisol is produced by the adrenal glands that sit next to the kidneys and is under fine control by signals from the pituitary gland in the brain. Most cases (85%) of Cushing’s disease are caused by a small benign tumour of the pituitary gland, which tells the adrenal glands to release too much cortisol. The minority of cases (15%) are caused by a tumour on one or other of the adrenal glands, leading to overproduction of cortisol from this affected gland.

In some cases, Cushing’s disease can also be caused by giving high doses of steroids over a prolonged period – this is called iatrogenic Cushing’s disease as it is caused by the administration of this medication, rather than a disease process in the body. It can be reversed by VERY CAREFULLY tapering the steroid dose, but this MUST be done following guidance by your vet, otherwise your dog could suffer from an Addisonian crisis (please see our Addison’s disease information sheet), which can be life-threatening.

What are the symptoms of Cushing’s Disease in dogs?

The symptoms of Cushing’s disease tend to progress gradually and can often be confused with other conditions, and the dog generally getting older. They usually include:

• Increased thirst and urination
• Increased hunger
• Pot-bellied appearance (abdominal swelling)
• Hair loss or slow hair growth
• Skin changes – skin thin/dark patches/calcium deposits
• Weight gain
• Lethargy
• Panting more than usual
• Lowered immunity – more prone to infections e.g. skin and urinary
• Loss of muscle tone

How is Cushing’s disease in dogs diagnosed?

Your vet may be suspicious of Cushing’s disease based on the clinical history and physical examination – affected dogs often have a typical ‘Cushingoid’ appearance. However, this will need to be confirmed using a combination of blood and urine tests, and possibly an ultrasound scan before treatment can be started.

How is Cushing’s Disease in dogs treated?

Treatment will depend on the underlying cause of the Cushing’s disease. In the majority of cases medication is recommended to reduce the production of cortisol to a normal level. You dog will need regular blood tests to ensure that the cortisol level is in the correct range and that the dose of medication does not need to be adjusted.

If your dog is taking medication for Cushing’s disease and they suddenly become unwell then please contact your vet immediately. On rare occasions, the cortisol level can be suppressed too much, leading to an Addisonian crisis. The symptoms of this are sudden weakness, vomiting, diarrhoea and collapse – it is an emergency and so your dog would need to be taken to the vets straight away.

For some cases of adrenal-dependant Cushing’s disease, where the overproduction of cortisol is caused by a tumour on the adrenal gland itself, surgery may be recommended, and this can be curative particularly in the case of benign tumours.

Can Cushing’s Disease in dogs be cured?

While most cases of Cushing’s cannot be cured, the majority of dogs can be well managed on long-term medication to suppress the cortisol level. Your dog will need regular monitoring at the vets, but with treatment most dogs will gradually get back to their normal selves and can live a happy life for many years.