Cushing’s Disease in Dogs: What You Need to Know

Is your dog slowing down, putting on weight and sleeping more?

If they are over a certain age, it’s possible that you’ve put these changes down to the dog’s advanced years.

But what if there was a condition that mimicked old age and, if treated, gave your dog back their mojo? You’d want to know about it, right?

Actually, such a condition does exist — it’s called Cushing’s disease.

Cushing’s disease is a common hormonal disorder that affects middle-aged and older dogs. This condition is rare in cats.

Cushing’s Disease in Dogs: An Overview

The symptoms of Cushing’s disease in dogs are caused by an excess of corticosteroid in the bloodstream, which causes increased thirst, thin skin, a potbelly and other signs.

The majority of cases are the result of cortisol-producing glands (the adrenal and pituitary glands) becoming overactive, whereas a small proportion are caused by tumors of these glands.

Certain dog breeds are at increased risk of developing Cushing’s disease, including:

• Beagles
• Boston Terriers
• Boxers
• Dachshunds
• Poodles

Symptoms of Cushing’s Disease in Dogs

Many people mistake the signs of Cushing’s disease for those of old age.

The dog gradually slows down, is less energetic and sleeps more.

Other common symptoms include:

• Weight gain
• Sagging stomach that takes on a potbellied appearance
• Dull and sparse coat
• Thin skin with blackheads
• Increased thirst, which increases water intake, resulting in possible lapses in toilet training

Another unfortunate consequence of Cushing’s is a high proportion of dogs developing high blood pressure. This makes an unexpected vascular incident, such as a stroke, more likely.

Indeed, experts in the field believe the high blood pressure associated with Cushing’s disease is the biggest single cause of sudden, unexplained death in older animals.

This video shows “Peggy dog,” a dog whose shaking is a result of Cushing’s disease:

What Causes Cushing’s Disease in Dogs?

Cushing’s disease (hyperadrenocorticism) is caused by an increase of the secretion of natural steroids, or cortisol, that stimulate the body to manufacture natural steroids.

It’s normal for the body to produce steroid at times of stress. It’s essential to cope with stress, and a lack of steroid makes a body very ill.

But too much (as with some things in life) is bad.

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A constant high level of cortisol leads to clinical signs such as thirst and a potbelly. An error in hormone production can originate from the pituitary gland in the brain or the adrenal gland next to the kidney.

Around 85–90% of cases are due to overactivity of these glands, with the remainder due to tumors.

Another form of Cushing’s is “iatrogenic” or “induced by medication.” This may happen if the patient is given high doses of oral steroids for a long time. The effect of the drug is the same, as if the body made the steroid, and in some cases clinical signs develop.

Your vet will discuss the risks of steroid medication with you should your dog require high doses to treat another medical condition.

Diagnosis

The vet may suspect Cushing’s from the history and certain changes on a routine blood panel. However, a definite diagnosis must be made before starting treatment.

A special “stimulation” blood test can give the answer.

There are 3 types of tests available, each looking at a slightly different point in the production line for steroid.

Unfortunately, though these tests are excellent, no one test is 100% foolproof. False negative or positives do occur.

If your vet thinks the test is not a true reflection of what he or she suspects, then it may be necessary to run a second type of test to check out a different part of the steroid manufacturing process.

If test results point toward an adrenal tumor, then an ultrasound scan of the kidney and adrenal gland is appropriate to look for signs of cancer.

Case Study: Meg the Staffie

Meg was once a lively dog. She was a star at her local agility club.

But over several months, her enthusiasm for exercise dwindled. Instead of jumping hurdles, she was more inclined to sleep.

She started to put on weight, which her family didn’t think too much about because Meg wasn’t burning calories as she used to.

She had also become thirstier — but again, given that Meg was no longer in the first flush of youth, her folks weren’t too concerned.

But that changed when Meg went on vacation with her family. Meg started having urinary accidents. When she came back from vacation, Meg’s family decided it was time for a checkup.

Classic Clinical Signs

I took a history and examined Meg. Her problem list looked something like this:

• Lack of energy
• Weight gain around the tummy (a potbelly)
• Drinking more
• Needing to pee more often
• Panting
• Poor coat
• Muscle loss on her back legs

All of this made me suspicious that Meg had Cushing’s disease.

Diagnosing Meg’s Condition

Reaching a diagnosis can be tricky.

In Meg’s case, I ran blood tests to see if her kidneys and other organs were healthy (they were), but certain changes on her results did hint at Cushing’s.

To confirm this growing suspicion, I ran a blood test that stimulates the body to produce steroid. We were able to put another puzzle piece into place: The results were consistent with a problem in the pituitary gland. We started treatment.

In other cases, the results are less clear-cut. Additional blood tests or an ultrasound scan of the tummy to search for enlarged adrenal glands may be necessary.

Once I reached a diagnosis, we checked Meg’s blood pressure. Hypertension (high blood pressure) is a common consequence of Cushing’s disease.

Indeed, Meg had very high blood pressure and was started on medication to target this issue.

If Meg reminds you of your older dog who is slowing down, bear in mind that a trip to your vet may well be the first step to help your pet get their old bounce back.

Treatment

The majority of cases respond to a once-daily oral treatment with trilostane (Vetoryl).

Just as Cushing’s disease comes on slowly, the signs reverse slowly. Once a dog is started on treatment, the Vetoryl is needed for life.

Those cases that do not respond are more likely to have a tumor. If the tumor is located in the adrenal gland, then surgery can be curative, but this is a tricky operation best undertaken at a specialist facility.

Once the dog is stabilized on Vetoryl, the blood pressure should be monitored. If it is high despite treatment, then adding in anti-hypertensive medication is essential to decrease the risk of sudden blindness or a stroke.

Can You Prevent Cushing’s Disease in Dogs?

There is no known method of preventing Cushing’s disease except for those iatrogenic cases induced by steroid medications.

In these cases, giving the steroid tablet on alternate days somewhat decreases the body’s dependence on the steroid and reduces the risk of inducing Cushing’s disease.

References

This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Dec. 17, 2018.

If you have questions or concerns, call your vet, who is best equipped to ensure the health and well-being of your pet. This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. See additional information.