Cushing’s Disease in Dogs

Cushing’s Disease in Dogs

If you have noticed that your dog is drinking more water and has been urinating much more frequently lately, this could be caused by a number of reasons, one of which is Cushing’s disease.

The disease is also known as hyperadrenocorticism or hypercortisolism and causes the abnormal release of the cortisol hormone. It can be caused by several conditions and is relatively common among adult and senior pups.

Cushing’s disease can cause multiple symptoms and the excess cortisol can prevent the body of the dog from being able to control stress, manage its healthy weight, control the blood sugar levels or fight infections.

Cushing’s can be tricky to diagnose and may require lifelong supportive medication.

To find out more about Cushing’s disease in dogs, as well as what causes it, how it is diagnosed, and how it is treated, go ahead and read our comprehensive guide about it.

What exactly is Cushing’s disease in dogs?

Cushing’s disease, which is often referred to as Cushing’s syndrome occurs when the body of the dog is exposed to high levels of cortisol for a long time. This can be caused by the body producing too much of it or from the prolonged use of corticosteroid medications.

Cortisol is the stress hormone which we commonly associate with the “fight or flight” response of the body. It is produced by the adrenal glands which are two peanut sized and shaped glands located in front of the kidneys. The production is controlled by the outer cortex of the glands.

The pituitary gland is a small gland which is located in the base of the dog’s brain, and it is in charge of signaling to the adrenal glands to release the cortisol hormone.

Most commonly, a benign tumor in the pituitary gland or less commonly in one of its adrenal glands can cause the release of excess amounts of cortisol in the body.

Cortisol is essential for the proper functioning of the body of the dog, so having too much of it or too little can cause different problems in canines.

As well as tumors in either the adrenal or pituitary glands, Cushing’s syndrome in dogs can be caused by the prolonged or high-level use of corticosteroids. Steroid medications are often used to treat allergies, immune disorders, cancer or other conditions in dogs. These medicaments can affect the cortisol levels in the dog’s bloodstream even if they are applied topically or in the form of ear drops.

Overall, Cushing’s disease is one of the most common endocrine disorders which affect dogs.

The disease often affects middle or old aged dogs, or in the case of steroid medication can affect pups of all ages.

The three common types of Cushing’s disease in dogs

Cushing’s syndrome can happen to dogs and all kinds of animals, and it can occur in humans too.

In dogs, the major types of Cushing’s syndrome are:

Pituitary dependent

This is the most common type of Cushing’s in dogs, and about 80 to 90% of the canines diagnosed with Cushing’s have this form. It is caused by a tumor in the pituitary which is a pea-sized gland located at the base of the brain.

The pituitary gland produces a number of different hormones including the ACTH. In cases of Cushing’s the tumor causes the overproduction of ACTH which travels to the adrenal glands through the bloodstream and triggers the adrenal glands to produce more cortisol than the body actually needs.

Adrenal-dependent

This is a less common type of Cushing’s disease in dogs. It happens as a result of a tumor in one of the adrenal glands which are located on top of the kidneys. Only about 15-20% of the dogs with Cushing’s syndrome have this type.

In this case, the tumor in the cortex of the adrenal glands causes the overproduction of cortisol.

Iatrogenic Cushing’s syndrome

This is Cushing’s disease caused by prolonged intake of corticosteroid medications. These are usually subscribed for allergies, immune system problems, some types of cancers and other conditions. They can include oral medications, as well as topical treatments or ear drops with steroids.

In these cases, the body of the dog has become exposed to too much cortisol hormone due to the intake of the steroids in large quantities or for a long time.

Depending on the type of Cushing’s disease, a different treatment will be prescribed by the vet.

The different types of Cushing’s can be diagnosed via blood tests, ultrasounds, x-rays and other methods we will discuss later.

The common symptoms of Cushing’s disease in dogs

You should keep in mind that all patients are different, so the symptoms can differ from one dog to another.

The vet will look at all of the symptoms present but will also run a number of diagnostics tests to confirm that the dog has Cushing’s disease.

Here are some of the most common symptoms you can expect to see in canines with Cushing’s:

  • An unusual increase in thirst and urination
  • Urinating during the night, and having accidents at home
  • An increased appetite
  • Increased panting
  • An enlarged, pot-bellied abdomen
  • Obesity or weight gain
  • Fat pads on the shoulders and the neck
  • Alopecia (hair loss)
  • Low energy levels
  • Weakness of the muscles
  • Skin darkening and pigmentation
  • Fragile or thin skin
  • Bruising of the skin
  • White, hard and scaly patches on the elbows or on the skin
  • Infertility
  • Chronic skin infections

What are the causes of Cushing’s disease in dogs?

In most cases, Cushing’s disease occurs naturally in dogs as a result of tumors either in the pituatary or the adrenal glands. In some cases, it can be caused by the intake of steroid medication as well as from chronic application of ear drops or topical gels or creams with steroids.

The latter can easily be resolved once the medications are stopped.

Some breeds have been found to be more prone to developing Cushing’s syndrome. These are Poodles, Boston Terriers, Dachshunds, Boxers, and Beagles.

The most common cause, in up to 90% of the cases is a benign pituitary tumor. These are very rarely malignant. In 10-15% of the cases, the syndrome is caused by tumors on one of the adrenal glands of the dog.

Identifying the cause of the disease is essential for prescribing and administering the appropriate treatment, as well as of the after-care and the prognosis for the dog.

In the cases of the pituitary gland tumor, the tumor can be either benign or malignant and can be microscopic or large. Depending on the type and size of the tumor, the dog will be assigned treatment and may require long-term or lifetime medication and veterinary supervision in order to live their lives normally.

Unfortunately, in about 15% of the dogs with pituitary gland tumors, the tumor is found to be growing. These types of tumors are known as macroadenomas and are larger than 1cm. As they grow, this may affect the brain of the dog. In these cases, the prognosis is not so good.

With adrenal gland tumors, the benign ones can be removed and the disease will be cured. In case it is malignant (carcinoma), the prognosis may not be so favorable, even though in some cases surgery can help. In these cases, the chances of the tumor being benign or malignant are about 50 -50%.

As for Cushing’s due to prolonged use of corticosteroids, also known as iatrogenic Cushing’s this can be resolved by stopping or reducing the steroids.

Diagnosis of Cushing’s disease in dogs

You should describe all the symptoms to the vet and also answer his or her questions about the health history of your pup.

After that a complete physical examination will be performed, including a blood chemistry profile, a complete blood cell count, as well as an analysis of the fecal matter and the urine of the dog.

Of based on these basic tests, your vet suspects that the dog has Cushing’s then he or she will most likely appoint more specific tests to diagnose the condition, as well as the type of Cushing’s.

The first test is usually a urine analysis which measures the cortisol and creatinine ratio in the dog’s urine. It the results of this test are alright, then it is not likely that the dog has Cushing’s.

If the ratio of the cortisol to creatinine is high, then further tests may be appointed.

The most common test for Cushing’s in dogs is the LDDST test (low dose dexamethasone suppression test. A blood sample is taken from the dog, and the baseline cortisol level is measured. After that, the dog is given a dexamethasone injection, and new blood samples are taken the cortisol levels after four and eight hours following the injection.

In normal dogs, this injection inhibits the secretion of the hormone which stimulates the production of cortisol, and this leads to lower cortisol levels in the blood. In cases when the dog has Cushing’s the levels will remain the same and will not be suppressed.

Then again, there is no one test which can be definitive for Cushing’s disease in absolutely all cases.

Your vet may also need to run an ACTH stimulation test, and to perform an ultrasound of the abdomen or a chest x-ray to determine whether the dog has Cushing’s and whether it is the pituitary or adrenal gland to blame, as well as whether the tumor in either of the glands is benign or malignant.

The ACHT stimulation test is used to measure how the adrenal gland works in response to AHCT which usually triggers them to produce cortisol. The test is done similarly to the LDDST test and the blood of the dog will be examined before and after the ACHT injection to determine the difference in the cortisol levels.

Still, there is no one single 100% accurate method for diagnosing Cushing’s, so most probably your vet will run a series of these and more tests to confirm the diagnosis, or reject it.

It is essential for the vet to be able to find out whether the dog has Cushing’s and what is causing it, in order to proceed with the appropriate treatment and management of the condition.

How will Cushing’s disease affect my dog?

Stress causes the release of cortisol in the body of the dog. The hormone tells the body it needs to work quickly and act quickly to fight off the stress (also known as “the fight or flight” reaction).

Under normal conditions, the body of the dog reacts by speeding up the metabolism and releasing more energy in the form of sugar and fat and holding on to the water.

Each time cortisol is produced the body reacts this way, so it comes to no surprise that Cushing’s when cortisol is released in large quantities can cause various changes in the body and health of the dog, including weight gain, skin infections or changes, hair loss, increased urination and increased thirst, an increased appetite.

Cushing’s also can make the dog more prone to developing diabetes, and other conditions.

This is why, it is essential that this disease is diagnosed properly and treated as early as possible, as to minimize the potential side effects of the overproduction of cortisol.

Treatments for Cushing’s disease in dogs

The treatment of Cushing’s caused by overuse of corticosteroid medications is pretty straightforward. The dog will be weaned off of the medication gradually because removing it too fast can cause Addisonian crisis which can be life-threatening in some cases.

Once the medication is no longer being administered, the cortisol levels will return back to normal and the dog will be cured.

Pups which have only mild symptoms of pituitary-dependent Cushing’s may not require immediate treatment. They should be monitored closely though to determine when treatment should begin or could be beneficial. The treatment is usually administered when the symptoms become more serious or dangerous for the dog or troublesome to the owner.

Such symptoms may include an increased urine protein to creatinine ratio which can mean kidney damage, high blood pressure, chronic infections, urinary accidents, and night-time urination, intolerance to exercise as well as excessive panting.

When the vet and owner decide to treat the pituitary-dependent Cushing’s, the dog will most likely be prescribed Veotryl (trilostane). This medication can cause serious side effects and can interact with other medications, so you must inform your vet about any other supplements or medications you are giving to the dog, and monitor it closely for adverse effects.

In case the dog is diagnosed with an adrenal tumor causing the Cushing’s, the vet will proceed to do chest radiographs or MRI or CT scans to see if there is a metastatic spread of the tumor. In case there are no metastases, the dog may be given trilostane. This medication can shrink the benign tumor in a few months and make it possible to be surgically removed.

Most vets will proceed to treat both adrenal and pituitary-dependent on Cushing’s syndrome with medication. Regular blood tests and monitoring of the condition of the dog will be appointed to determine how it is responding to the treatment, and to the medication, and if necessary to adjust it or change it.

Trilostane (Vetoryl)

Vetoryl (trilostane) has been approved by the FDA for treatment of both adrenal and pituitary-dependent Cushing’s in dogs. It works by stopping the cortisol production by the adrenal glands.

Some dogs should not be given trilostane if they have the following underlying conditions:

  • Liver or kidney disease
  • Has heart disease and takes certain types of medications for the condition
  • If the dog is pregnant

The most common side effects of trilostane on dogs are:

  • Reduced appetite
  • Vomiting
  • Diarrhea
  • Energy lack and weakness

Some more serious adverse effects of the drug include:

  • Bloody diarrhea
  • Severe sodium-potassium imbalance
  • Elevated liver enzymes
  • Elevated kidney tests
  • Adrenal insufficiency
  • Shaking
  • Collapsing
  • Destruction of the adrenal gland
  • Death

Other drugs for Cushing’s in dogs

Anipryl (selegiline) is the only other drug approved by the FDA for treating Cushing’s disease in dogs but only for the cases of pituitary-dependent uncomplicated Cushing’s.

Some vets also use the human chemotherapy drug Lysodrene (mitotane) to treat this condition in dogs.

Lysodrene destroys the layers which produce the cortisol in the adrenal glands. It too can have severe side effects and requires close monitoring of the dog.

This practice is known as off-label prescribing which vets can do when prescribing human drugs to animals but at a different dosage and with close monitoring of the reaction of the dog to the medicine.

Overall, the treatment for Cushing’s is like a balancing act. With regular monitoring and adjustment of the medicine, the dog can lead a good normal life.

Still, in most cases, the medication will need to be administered for life, and regular blood tests and check-ups will need to be performed for the rest of the dog’s life.

The dog parent needs to follow the treatment plan closely and monitor the symptoms and behavior of the dog. By doing this, and working closely with the vet to keep the condition under control, your dog with Cushing’s disease can lead a happy and healthy life.

In many cases of adrenal-dependent Cushing’s, the vets may be able to surgically remove the tumor on the adrenal gland, but only if it hasn’t spread to other organs and body parts. If the tumor is removed completely and is not benign there are chances that the dog will regain its normal health after the surgery.

The prognosis for dogs with Cushing’s disease

The prognosis for dogs with Cushing’s disease is about two years. About 10% of the dogs do live beyond four years after being diagnosed with the disease.

This doesn’t mean though that Cushing’s causes the death. The death usually occurs due to old age or other causes, because Cushing’s is most commonly found in dogs which are older.

If the pituatary tumor is small and isn’t growing and affecting the brain, the dog with pituatary-dependent Cushing’s can still live happily for many years, with the proper medication administered along with regular monitoring.

If the dog has an operatable benign adrenal tumor causing the disease, it can be completely cured when the tumor is removed.

With pituatary tumor surgery, about 85-95% of the dogs restore their hormonal balance as well as the symptoms and the other neurological symptoms.

Unfortunately, the fact that a dog is treated for either type of Cushing’s will not prevent the development of the other type at the same time. So, this is something to watch for too.

Living and managing Cushing’s disease in dogs

In some cases, like in corticosteroid-related Cushing’s or when the tumor in the adrenal or pituitary gland can be removed completely, Cushing’s disease in dogs is curable.

In other cases, the disease can be managed with medications for the rest of the pet’s life.

Alongside with the medication, dog parents will need to monitor their dog continuously and take it on regular check-ups at the vet, so that the reaction to the medication and the treatment can be monitored, and if required – adjustments to the dosage or medication are made.

If your pup is being treated with trilostane, you should be careful about the side effects this medication can have on some dogs.

Some common adverse side effects of this medicament include a lack of appetite, vomiting, diarrhea, weakness, lack of energy, difficulty walking and others.

In case you notice one or more of these side effects, you should contact your vet as soon as possible for advice on whether you should stop the medications or change the dosage.

Your vet will schedule regular check-ups and follow-ups, which will include physical examinations of the dog, taking blood samples and discussing any ongoing symptoms.

Most pups can be treated with this or other medication for Cushing’s successfully and with little or no serious side effects.

It is a game of balancing the dosage and the medication to suit the health and wellbeing of the dog, so it will require regular visits to the vet and careful monitoring of the dog.

Overall, if you follow the treatment plan and go to the scheduled checkups, your dog can live its life happily for the rest of its days.

Keep in mind, that the ongoing blood tests and physical examinations, as well as the medication itself,  can be pretty costly. But on the other hand, your dog can live its life to the fullest if you invest in its proper treatment and care!

Unfortunately, with pups that have tumors which are malignant and metastatic, the prognosis is not so bright, but again, today’s veterinary medicine has advanced a lot, so if you find the right vet, you can be sure that everything that can be done for the ailing dog will be done.

Good luck with your dog, and we hope it gets the proper treatment and gets better soon!