What Causes Cushing’s Disease in Dogs? A Vet’s Simple Guide

You’ve probably used cortisone at some point in your life. It’s the ingredient in anti-itch creams that makes your kid’s bug bites feel better.

Cortisone is a synthetic version of the hormone cortisol that occurs naturally in animals including humans and dogs. It acts as an anti-inflammatory and helps control important metabolic functions including fat storage and blood sugar. 

What Is the Cause of Cushing’s Disease in Dogs?

Cortisol is a hormone produced by the adrenal glands. There are two adrenal glands and each one is on the front end of a kidney. The kidneys and adrenal glands are located in a dog’s abdomen around the mid-back area. 

The symptoms seen in Cushing’s disease result from too much cortisol in a dog’s body over a long period of time. The three main causes of excess cortisol are: 

  1. Benign tumor on the pituitary gland in the brain over-stimulating the adrenal glands (pituitary-dependent Cushing’s disease)
  2. Tumor growing in one of the adrenal glands making too much cortisol (adrenal-dependent Cushing’s disease)
  3. Synthetic steroid hormone medication like prednisone, given over a long period of time (iatrogenic Cushing’s disease)

Since pituitary tumors cause about 80-85% of canine Cushing’s disease cases, that is the focus of this article.

Cushing’s disease is relatively uncommon, occurring somewhere in only about 0.17-0.20% of the dog population (3,7)

What causes Cushing's disease in dogs? (older Boston Terrier)
Boston Terriers are prone to getting Cushing’s disease as they get older.

Dog Breeds Prone to Cushing’s Disease

Any breed of dog can get Cushing’s disease, but certain breeds are more likely to develop the problem. Middle-aged to elderly dogs are at higher risk than younger dogs. 

Breeds prone to getting Cushing’s disease include:

  • Bichon Frise
  • Border Terrier
  • Boston Terrier
  • Dachshund
  • Fox Terrier
  • Jack Russell Terrier
  • Lhasa Apso
  • Miniature Schnauzer
  • Staffordshire Terrier
  • Standard Schnauzer
  • Yorkshire Terrier

What Are the Symptoms Of Cushing’s Disease in a Dog?

The most common symptoms of Cushing’s disease in dogs are increased drinking, increased urination and increased appetite. 

Some dogs also have skin problems, itching, hair loss, panting, weight gain, pot-belly and lethargy. 

Other clinical signs that occur occasionally in Cushingoid dogs include sudden blindness, facial nerve paralysis and lung blood clots. 

How Do Vets Test For Cushing’s Disease in Dogs?

When a vet suspects a dog has Cushing’s disease, they will order a basic lab profile with a CBC, blood chemistry, thyroid test and urinalysis. 

They will add on adrenal function tests if the suspicion is high or if initial tests support the suspicion.

Vets rely on an ACTH stimulation test or low-dose dexamethasone suppression test to definitively diagnose a dog with Cushing’s disease. These tests take 1 to 8 hours to collect all the samples.

Abdominal ultrasound is often recommended to make sure there are no tumors on the dog’s adrenal glands.

What Is the Cost of Cushing’s Disease Testing in Dogs?

The cost of Cushing’s blood test may be in the range of $200 to $500. Other tests, including blood tests, urinalysis, x-rays and abdominal ultrasound can add another $500-$1000 to the bill. Embrace Pet Insurance reports $500-$1500 for a complete diagnosis of Cushing’s disease in dogs. 

In most cases, testing will give your vet the information to make a diagnosis of Cushing’s disease. Occasionally test results are not clear as to whether or not a dog has the disease. 

What Medication Is Used to Treat Cushing’s Disease in Dogs?

Drugs that suppress the production of cortisol in the adrenal gland are the most reliable treatment for Cushing’s disease. Currently, the most commonly prescribed treatment for Cushing’s disease is trilostane, brand name Vetoryl®. 

Vetoryl works well to stop the symptoms of Cushing’s disease in most dogs by blocking cortisol production in the adrenal glands. It comes as an oral capsule a dog takes once or twice a day for the rest of their life.

Dogs taking Vetoryl must be monitored closely throughout their lives by their owners, their vet and lab tests. The dosing must be adjusted to suppress the production of cortisol enough to alleviate symptoms but avoid suppressing it too much. 

If a dog takes too much trilostane, they won’t make enough cortisol to maintain normal body functions and will get very sick. 

What Is the Cost of Cushing’s Medication Cost for Dogs?

The cost of Vetoryl is somewhere around $150-$300 per month for a 50-pound dog and $70-$150 for a 10-pound dog. 

Don’t forget to include the cost of vet rechecks and lab tests for monitoring the medication when you’re calculating the total cost of treatment. 

Vet rechecks and labs are done frequently at the beginning of treatment and about every 3 months after the dog has stabilized. These might add another $1500-$2500 per year, depending on where you live. 

A ballpark estimate to diagnose, treat and monitor a dog with Cushing’s disease is around $2500-$6000 per year. It’s cheaper than human Cushing’s treatment, but it’s still not something to be taken lightly!

Alternative Cushing’s Treatments: Anipryl, Melatonin and Lignans

Selegiline (Anipryl®) is an oral monoamine oxidase inhibitor made initially to treat canine cognitive dysfunction syndrome. It also decreases the production of ACTH in the pituitary gland which is produced in excess in pituitary-dependent Cushing’s disease. 

If you’re hesitant to use trilostane, it’s worth giving Anipryl a try. Unfortunately, Anipryl only works in about 20% of symptomatic Cushingoid dogs. (2)

Melatonin is an oral synthetic hormone supplement used by people to help them sleep. It has also been promoted to treat Cushing’s disease in dogs, usually in combination with flax lignans. 

One study showed the combination of melatonin and lignans decreased cortisol production from adrenal gland tumor cells in the lab. We don’t have any evidence that the same thing happens in living dogs. Most vets who have tried this combo therapy report the treatment was ineffective. (5)

Dog Food Recommendations for Cushing’s Disease

There is no specific diet to help dogs with Cushing’s disease. If your dog has a problem like protein in their urine or recurrent bladder infections as a result of having Cushing’s disease, ask your vet about prescription diets to help with those secondary conditions. 

The primary dietary goal for dogs with Cushing’s disease is to maintain lean body mass and prevent obesity. Look for dog food with a nutrient profile similar to this:

NutrientRecommended Percentage of Dry Matter
Protein25-30%
Fat5-15%
Fiber5-20%

One good option is Hill’s prescription dog food called Metabolic + Mobility. This food also has ingredients to alleviate symptoms of arthritis. 

If you prefer non-prescription dog food, take a look at the Purine Pro Plan line, specifically Purina Pro Plan Weight Management Adult Dry Dog Food & Wet Dog Food.

Prognosis for Cushing’s Disease in Dogs

The prognosis is good for 80% of dogs who get good treatment and monitoring for pituitary-dependent Cushing’s disease. And quality of life is very good for most of these dogs and their owners. 

Based on the results of a 2017 study (6), the median life expectancy for dogs with untreated pituitary-dependent Cushing’s disease was 506 days (1.4 years). In another study, dogs treated with low-dose twice a day trilostane had a median survival time of 900 days (2.5 years). (4).

Treated vs. Untreated Cushing’s in Dogs

So, looking at the survival times, you may ask if you should treat your dog for Cushing’s disease. My recommendation in most cases is to treat the dog with trilostane because of the quality of life improvements it brings. 

Untreated Cushingoid dogs are tired, weak, thirsty and hungry all the time. These symptoms are not only annoying to dog owners, they also affect a dog’s quality of life.

Properly treated Cushingoid dogs remain comfortable even if their lifespan is not much longer than untreated dogs. 

However, if you can’t provide close monitoring and repeated testing, treatment may be frustrating or even dangerous to your pup. 

Should All Dogs With Cushing’s Disease Be Treated?

Just because a dog has test results consistent with Cushing’s disease it doesn’t always mean they should be treated.

Veterinary endocrinologists do not recommend treating dogs who show very mild or no symptoms of Cushing’s disease. Cushing’s disease progresses slowly over weeks to months, so you can reconsider treatment if symptoms get worse.

Some dogs with untreated Cushing’s disease develop secondary problems like urinary tract infection, high blood pressure and skin problems. In those cases, treatment is recommended even if the dog doesn’t have the more common symptoms of Cushing’s disease. 

Is There a Way to Prevent Cushing’s Disease in Dogs?

Many dog owners wonder if they can do anything to prevent Cushing’s disease from developing. Unfortunately, there is no known way to prevent a dog from getting the disease at this time. 

If you plan to buy a dog breed that is prone to the disease, ask the breeder a lot of questions about whether the family line has a history of Cushing’s disease. You can also avoid adopting pups from the more susceptible breeds. 

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References

  1. Barker, E. N., Campbell, S., Tebb, A. J., Neiger, R., Herrtage, M. E., Reid, S. W. J., & Ramsey, I. K. (2005). A comparison of the survival times of dogs treated with mitotane or trilostane for pituitary‐dependent hyperadrenocorticism. Journal of Veterinary Internal Medicine, 19(6), 810-815.
  2. Behrend, E. N., & Melian, C. (2013). Hyperadrenocorticism in dogs. Clinical Endocrinology of Companion Animals, 43-64.
  3. Carotenuto, G., Malerba, E., Dolfini, C., Brugnoli, F., Giannuzzi, P., Semprini, G., … & Fracassi, F. (2019). Cushing’s syndrome—an epidemiological study based on a canine population of 21,281 dogs. Open Veterinary Journal, 9(1), 27-32.
  4. Clemente, M., De Andrés, P. J., Arenas, C., Melian, C., Morales, M., & Pérez‐Alenza, M. D. (2007). Comparison of non‐selective adrenocorticolysis with mitotane or trilostane for the treatment of dogs with pituitary‐dependent hyperadrenocorticism. Veterinary Record, 161(24), 805-809.
  5. Fecteau, K. A., Eiler, H., & Oliver, J. W. (2011). Effect of combined lignan phytoestrogen and melatonin treatment on secretion of steroid hormones by adrenal carcinoma cells. American journal of veterinary research, 72(5), 675-680.
  6. Nagata, N., Kojima, K., & Yuki, M. (2017). Comparison of survival times for dogs with pituitary‐dependent hyperadrenocorticism in a primary‐care hospital: treated with trilostane versus untreated. Journal of Veterinary Internal Medicine, 31(1), 22-28.
  7. Schofield, I., Brodbelt, D. C., Niessen, S. J. M., Church, D. B., Geddes, R. F., & O’Neill, D. G. (2021). Frequency and risk factors for naturally occurring Cushing’s syndrome in dogs attending UK primary‐care practices. Journal of Small Animal Practice.