Cushing's disease in dogs: causes, symptoms, and treatment

27 July 2023 - 6 min read
Alaskan Klee Kai dog is sitting on a wood floor in front of a fireplace. This dog has Cushing's disease and one of the side effects is extreme thirst and panting. The red on his coat is from excess hormone secretions that are also caused by the disease

When hormone levels go awry, dogs can get very ill. A good example is Cushing’s disease, which is almost always caused by too much of the stress hormone cortisol.

Cushing’s disease (also called hyperadrenocorticism, Cushing’s syndrome, and hypercortisolism) is one of the most common hormonal diseases in dogs.

At ManyPets, we dealt with 453 pet insurance claims for Cushing's in dogs in 2022. That's just over 0.5% of our total canine illness claims, so it's a relatively common condition.

Cushing's can be serious, but it is treatable. Here's what you need to look out for and how to help your dog if they develop the disease.

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What causes Cushing's disease in dogs?

Most cases of Cushing’s disease in dogs (80-85%) are caused by a benign tumour in the pituitary gland that overstimulates the adrenal glands.

The pituitary gland is located at the base of the brain and makes adrenocorticotropin hormone (ACTH) to control the production and secretion of cortisol from the adrenal glands. Cushing's disease stemming from a tumour in the pituitary gland is often called pituitary-dependent hyperadrenocorticism, or PDH.

The other 15-20% of Cushing's Disease cases are caused by adrenal tumours. About half of those tumours are benign and the other half being malignant (cancerous).

A dog's adrenal glands lie right on top of its kidneys and are the primary producers of cortisol. Cushing’s disease arising from an adrenal tumour is referred to as adrenal-dependent hyperadrenocorticism, or ADH.

A third type of Cushing’s disease, called iatrogenic Cushing’s disease, can be caused by corticosteroid medications, like prednisone and dexamethasone, that act like cortisol in the body. High doses or long-term corticosteroids given orally, by injection, or even topically can lead to Cushing’s disease in some dogs.

Other types of Cushing’s disease have also been reported but are rare.

Which dogs are most susceptible to Cushing's disease?

Cushing’s disease is most commonly diagnosed in middle-aged or older and senior dogs.

In fact, 94% of the claims we saw for the disease in 2022 were in dogs aged seven or older. Almost half (47%) were in dogs aged at least 10.

Smaller dogs (less than about 18kg) more commonly develop PDH, while larger dogs have an equal risk of PDH and ADH.

According to our historic claims data, the breeds most commonly affected by Cushing's disease are:

  1. Jack Russell

  2. Staffordshire Bull Terrier

  3. Border terrier

  4. Shih Tzu

  5. Lhasa Apso

  6. Bichon Frise

  7. Yorkshire Terrier

Smaller breeds dominate the list, but some larger breeds are also affected. The larger breeds with the most pet insurance claims for Cushing's are:

  1. Newfoundland

  2. Irish Setter

  3. Labrador Retriever

Life expectancy for dogs with Cushing's disease

Dogs with Cushing's disease who have surgery to remove an adrenal gland tend to live for another 18 months to four years.

While these numbers may not sound impressive, it's important to realise that the average age at diagnosis for dogs with Cushing's disease is 11 years.

There are also some drugs used to treat Cushing's Disease. Mitotane or trilostane for PDH generally leads to a survival time of around two years.

Symptoms of Cushing's disease in dogs

Too much cortisol over extended periods leads to problems.

The typical symptoms of Cushing’s disease in dogs are:

  • Increased appetite

  • Increased thirst and urination

  • Coat and skin problems

  • Recurrent infections

  • Panting

  • Muscle weakness

  • A pot-bellied appearance

Dogs with large pituitary tumours may also develop neurologic problems like behavioural changes, circling, and seizures.

Talk to your vet if your dog has any of these symptoms and make sure they have at least an annual vet check as they age. The earlier health problems are diagnosed, the easier they are to manage.

How to tell if your dog has Cushing's disease

Your vet will need to carry out diagnostic testing to find out whether your dog has Cushing’s disease.

There is no single test that will accurately diagnose Cushing’s disease in all dogs, so your vet will need to gather information from various sources and tests to make a diagnosis.

They'll start with a health history and physical examination, followed by a basic panel of lab work that includes a complete blood count, a blood chemistry panel, and a urinalysis. The results may point towards Cushing’s disease or other health problems that could be to blame for your dog’s symptoms.

Next, the veterinarian may run an inexpensive and simple test called a urine cortisol to creatinine ratio (UCCR). If it is high, your dog might have Cushing’s disease. If it's normal, they probably don’t.

There can be other reasons for your dog's high UCCR, so the vet will probably want to do some more tests to determine if your dog truly does have Cushing’s disease.

They may run an ACTH stimulation test or a low-dose dexamethasone suppression.

Both of these tests can be expensive and your dog will need to stay at the vets for a few hours so multiple blood samples can be taken.

Your vet will also need to find out whether your dog has PDH or ADH. Sometimes a low-dose dexamethasone suppression test can provide this information, but often the vet will need to run more tests.

Options include:

  • a high-dose dexamethasone suppression test

  • an endogenous ACTH test

  • an ultrasound of the dog’s abdomen

  • a CT scan or MRI of the dog’s abdomen or brain

Your veterinarian can determine which combination of tests is most likely to lead to an accurate diagnosis.

Cushing's disease treatment options for dogs

The right treatment for Cushing’s disease will depend on the type of dog and how severely affected they are.

Dogs with PDH who have only mild symptoms may not need immediate treatment, but they should be closely monitored.Treatment is necessary once the symptoms are bad enough that they’re disrupting your dog's quality of life, or yours.

Your vet will typically prescribe oral mitotane or trilostane to lower the amount of cortisol the adrenal glands produce. Removing a pituitary tumour through surgery or radiation therapy may be an option, particularly if your dog has neurological symptoms.

If an adrenal tumour is responsible for your dog’s Cushing’s disease, surgically removing the affected adrenal gland is the treatment of choice. Dogs with benign adrenal tumours can be cured with surgery, but this is usually not the case if the tumour is malignant.

Removing an adrenal gland is difficult, so your vet may refer your dog to a specialist veterinary surgeon.

Radiation therapy or medical management with mitotane or trilostane can be considered when surgery is not appropriate.

Dogs with iatrogenic Cushing’s disease need to be slowly tapered off their corticosteroid medications.Oftentimes, the disease that was being treated with steroids will flare up again and need to be managed in another way.

Managing cushing's disease in your dog

Most dogs with Cushing’s disease need lifelong veterinary care. For example, dogs with PDH have to be closely monitored to ensure they’re getting an appropriate dose of mitotane or trilostane and to look out for potential side effects of the treatment.

Initially, your dog may need to go to the vet frequently for testing, but the eventual goal is to try to stretch out re-checks to every three to six months.

If your dog’s condition starts to get worse or you notice any new symptoms, see your vet for advice. It’s not unusual to have to adjust a dog’s treatment as their Cushing’s disease progresses.

Does dog insurance cover Cushing's disease?

Diagnosing, treating, and managing Cushing’s disease is complicated and can get expensive, but your dog insurance should help cover the cost if you took out cover before they became unwell.

Most vets recommend lifetime pet insurance as these policies have a vet fee limit that refreshes each year. That makes them suitable for chronic conditions like Cushing's disease.

It's a good idea to insure your dog when they’re young so that chronic conditions, like Cushing’s disease, can be covered. If you wait until your dog's already ill before you take out a policy their Cushing's is likely to be considered a pre-existing condition.

Our Pre-existing policy can cover recent conditions.

Jennifer Coates, DVM
Veterinarian, Veterinary Writer, Editor, and Consultant

Dr. Jennifer Coates is a writer, editor, and consultant with experience in veterinary medicine, science, animal welfare, conservation, and communications. She has written for outlets including petMD, Chewy, and ManyPets.