Cushing’s Disease in Dogs: Symptoms, Causes, and Treatments

Cushing’s Disease is an often misunderstood health condition affecting both middle-aged and senior dogs. An endocrine-based disorder, Cushing’s Disease can have serious, life-threatening consequences if left untreated - an intimidating diagnosis for the unsuspecting owner!

Understanding the various aspects of Cushing’s Disease in dogs can make all the difference when it comes to proper long-term management of this chronic condition. Though not a preventable illness, most dogs with well-controlled Cushing’s Disease will be able to live long and happy lives well into their senior years.

Today, we’re going to take a thorough look into the world of Cushing’s Disease in our furry friends. Not only are we going to investigate the most common causes of this condition and the first warning signs, but we’re also going to explain what Cushing’s Disease is and how it may affect a dog’s overall quality of life. Let’s get started!

What is Cushing’s Disease in Dogs?

Cushing’s Disease in dogs is a semi-rare endocrine disorder characterized by an excess production of cortisol (the body’s stress hormone). The medical term for this condition is hyperadrenocorticism, and it breaks down literally to mean:

Hyper (over-active) - Adreno (of the adrenal gland) - Corticism (of the cortex or “outer part” of the adrenal gland).

But to fully understand what Cushing’s Disease is and its associated risks, we must first understand what cortisol is and why it’s so important.

Cortisol - The Stress Hormone

Cortisol is known as the stress hormone, and its most important job is to help your dog’s body manage and respond to stress. Cortisol is produced by the adrenal glands and is largely responsible for suppressing inflammation and regulating blood pressure, among other vital functions that can be impacted by outside stressors.

Not only does cortisol help your dog respond appropriately to stress, but it can also help regulate your pup’s body weight, skin condition, and other such features of good health. But when the adrenal glands are forced to produce more cortisol than needed, problems begin to arise.

An overabundance of cortisol in the body can lead to the following:

• Increased Blood Sugar Levels
• Elevated (High) Blood Pressure
• Excessive Weight Gain
• Suppression of the Immune System
• Heart Disease

Each of these issues, if left untreated, can be life-threatening, and, in many cases, Cushing’s Disease is to blame. Unfortunately, the symptoms of this condition are often very subtle and gradual, happening slowly over time versus all at once.

Though signs may be subtle, this condition is often characterized by symptoms such as increased thirst or hunger and the appearance of a bloated (pot-belly) abdomen. While not considered a common disease, experts estimate that Cushing’s Disease will affect approximately one in two-hundred dogs.

What Causes Cushing’s Disease in Dogs?

The three main causes of Cushing’s Disease in dogs are pituitary tumors, adrenal tumors, or prolonged use of steroid medications.

Pituitary Tumors

The pituitary gland is a small, bean-shaped organ that sits at the base of the brain. Often referred to as the “master” gland of the endocrine system, the pituitary gland is responsible for the production and management of several essential hormones and other important endocrine system glands.

One of the essential hormones that the pituitary gland produces is the adrenocorticotropic hormone (ACTH). The key function of this particular hormone is to stimulate the production and distribution of cortisol from the cortex (the outer part of the adrenal gland).

When a tumor develops on the pituitary gland, it causes an increase in the production of the adrenocorticotropic hormone (ACTH), thus stimulating the adrenal glands to produce more cortisol than the body actually needs. And, as we’ve learned, too much cortisol in the body can be detrimental to a variety of essential functions.

Pituitary tumors can either be malignant (cancerous) or benign (non-cancerous) and are the leading cause of Cushing’s Disease in dogs. In fact, according to the U.S Drug and Food Administration, approximately 80-85% of Cushing’s cases are caused by pituitary tumors.

Adrenal Tumors

Adrenal tumors are a common cause of Cushing’s Disease, second only to pituitary tumors. But what exactly are the adrenal glands?

The adrenal glands are two small, triangular-shaped glands located above the kidneys. These glands are an important part of a dog’s endocrine system and are responsible for the production of several essential hormones, such as cortisol and adrenaline.

When a tumor develops on the adrenal glands (either one or both), it stimulates the production of excess cortisol, which can lead to weight gain, elevated blood pressure, and other serious health problems.

According to the FDA, only 15-20% of Cushing’s Disease cases are caused by adrenal tumors. And according to the Veterinary Information Network (VIN), half of these tumors will be malignant (cancerous), while the other half will be benign (non-cancerous).

Adrenal tumors can be surgically removed, though the course of action that a veterinarian will recommend in this case will largely depend on which type of tumor the patient has.

Prolonged Use of Steroids

The third and least-common cause of Cushing’s Disease in dogs is prolonged or high-dose usage of steroid medications, such as Prednisone. The term for this particular condition is Iatrogenic Cushing’s Syndrome (ICS).

The word iatrogenic, in reference to a medical condition, is defined by Webster’s Dictionary as “induced unintentionally by a physician or surgeon or by medical treatment or diagnostic procedures.”

The key word in this scenario is unintentional - most veterinarians will only use steroids as a last resort and in response to a chronic or persistent condition that is causing a patient discomfort, such as atopic dermatitis or canine asthma.

To reduce the risk of long-term side effects such as ICS, steroids will usually be prescribed at a dose that tapers down over time or in combination with other medications. However, there are some scenarios in which long-term steroid use is unavoidable, such as with cancer treatment.

Iatrogenic Cushing’s Syndrome is sometimes referred to as “False Cushing’s” because, unlike pituitary-dependent or adrenal-dependent cases of Cushing’s, ICS is a curable condition. In fact, most cases of ICS can be reversed by simply reducing or withdrawing the problematic steroid medication.

Symptoms of Cushing’s Disease in Dogs

Cushing’s Disease can be difficult to diagnose because the symptoms are often very subtle and develop gradually over time. Additionally, many of the defining symptoms of this condition, such as increased thirst and urination, are shared with other, more prevalent conditions as well.

This factor, alone, can make it difficult for a veterinarian to determine where to look first. With Cushing’s being a semi-rare condition, it may not be the first thing that comes to mind when searching for a diagnosis.

Common symptoms of Cushing’s Disease in dogs include:

• Increased Thirst and Urination
• Increased (Insatiable) Appetite
• A Distended or “Pot-Belly” Abdomen
• Excessive Panting
• Lethargy or Drowsiness
• Muscle Weakness
• Recurring Urinary Tract Infections (UTIs)
• Hair Loss or Thinning
• Skin Acne or Pustules
• Red, Irritated, or Flaky Skin

The symptoms of Cushing’s do not typically vary based on the type or cause of the condition, though they may differ in severity based on factors such as age, gender, and the strength of a dog’s immune system.

How to Test for Cushing’s Disease in Dogs

There are a few different ways to diagnose Cushing’s Disease in dogs, with two of the most reliable diagnostic options being an ACTH Stimulation Test and a Low-Dose Dexamethasone Suppression Test.

ACTH Stimulation Testing

An ACTH Stimulation Test is designed to measure the performance of a dog’s adrenal gland function in response to an injection of synthetic adrenocorticotropic hormone (ACTH) over several hours.

To start, your veterinarian will draw a small sample of your dog’s blood before administering an injection of synthetic ACTH. Exactly one hour after this injection is given, your veterinarian will draw a secondary sample. This process will sometimes be repeated at hour three as well, depending on the requirements of the testing facility and your veterinarian’s own preference.

When the levels of cortisol in each sample are compared, they will show one of three responses: normal response (indicating your pet does NOT have Cushing’s Disease), very little response (indicating adrenal insufficiency, which is the opposite of Cushing’s), or exaggerated response (providing confirmation of Cushing’s Disease).

The ACTH Stimulation Test is an incredibly helpful tool for diagnosing Cushing’s Disease, though it does not provide any indication of the type of Cushing’s that a dog has (pituitary-based versus adrenal-based). To determine the type at hand, your veterinarian may recommend a subsequent test known as a Low-Dose Dexamethasone Suppression Test (LDDS).

Low-Dose Dexamethasone Suppression Testing

A Low-Dose Dexamethasone Suppression Test (LDDS) is a diagnostic measure used to confirm the presence of Cushing’s Disease, as well as to identify the type that is present. As we’ve learned, there are two primary types of Cushing’s in dogs: pituitary-dependent and adrenal-dependent. Knowing which specific type of illness your dog is dealing with is essential for selecting an appropriate treatment plan.

The goal of a Low-Dose Dexamethasone Suppression Test is to determine whether or not cortisol secretion (guided by the pituitary gland) can be suppressed. To perform this test, your pet will have a baseline blood sample drawn before receiving an injection of Dexamethasone (a synthetic, man-made glucocorticoid). He will then have his blood drawn at exactly four and eight hours following this injection.

Each blood sample will then be evaluated for cortisol concentration. If the results show that the cortisol levels were not at all suppressed following an injection of Dexamethasone, the patient is confirmed to have adrenal-dependent Cushing’s Disease. If, however, the cortisol levels were suppressed but not appropriately (or as much as they should’ve been in a healthy dog), the patient is confirmed to have pituitary-dependent Cushing’s.

While this type of test is not inexpensive, it can be a valuable way to determine precisely what condition your pet is dealing with, which can help your veterinarian accurately determine the best possible course of treatment.

Abdominal Ultrasound and MRI

Once your pet has been diagnosed with Cushing’s Disease, your veterinarian may also recommend an abdominal ultrasound or MRI to measure the size and location of the problematic tumor. An abdominal ultrasound will allow your vet to visualize an adrenal tumor, while an MRI will provide visualization of a pituitary tumor.

Cushing’s Disease in Dogs Treatment

Cushing’s Disease can be a complicated and frustrating condition to manage, but it is treatable with the right approach. In most cases, treatment for this condition involves the use of daily medication along with a few simple lifestyle changes, though more serious cases may require surgical intervention.

Medication for Treating Cushing’s Disease in Dogs

Thanks to modern medicine, there are several great medications available today for managing a dog with Cushing’s Disease. Four of the most popular are Trilostane, Selegiline Hydrochloride, Ketoconazole, and Melatonin (that’s right - the same Melatonin that helps you sleep).

Trilostane (Vetoryl)

Trilostane is the go-to drug for the treatment of Cushing’s Disease in dogs. Commonly known by its brand name Vetoryl, trilostane effectively keeps Cushing’s under control by preventing the production of cortisol in the adrenal glands. This medication is effective for both pituitary-dependent and adrenal-dependent Cushing’s Disease and, according to a 2018 study by the Canadian Veterinary Journal, approximately 67-100% of dogs will be well-controlled after just six months of treatment with trilostane.

Selegiline Hydrochloride (Anipryl)

Selegiline Hydrochloride, also known as Anipryl, is the only other FDA-approved drug (besides trilostane) for the treatment of uncomplicated, pituitary-dependent Cushing’s Disease. Anipryl’s job is to prevent the pituitary gland from over-producing cortisol, and it does this by preventing the breakdown of dopamine in the brain, which, in turn, inhibits the creation of ACTH in the pituitary gland.

The only downside? Anipryl is only effective in about 20% of pituitary-dependent cases of Cushing’s Disease.

Though the vast majority of Cushing’s cases are pituitary-dependent, only 20% of those cases have tumors that are on the specific part of the pituitary gland that is dependent on dopamine. This means that 80% of dogs with this specific type of illness will not see any major benefit from Anipryl.

Ketoconazole

Primarily known for its antifungal properties, Ketoconazole can actually be a helpful medication for the treatment of Cushing’s Disease in dogs. Though scientists are still a bit stumped as to how exactly it works, Ketoconazole has been shown to prevent the rise of ACTH secretion, thereby preventing the overproduction of cortisol.

In fact, a 2008 study by the Journal of the American Veterinary Medical Association revealed just how effective Ketoconazole really is for this purpose, stating that 90% of participating dogs showed evidence of clinical improvement during the trial period.

Melatonin

Melatonin has long been appreciated for its calming properties, helping both humans and animals sleep more peacefully at night while reducing stress and anxiety during the daytime. But did you know that Melatonin can also be an effective way to treat mild cases of Cushing’s Disease as well?

According to Dr. Morgan, a consultant for Pet MD, Melatonin is a safe and effective way to treat this condition, as it “helps the body block the uptake of increased cortisone caused by a benign tumor on the pituitary gland.”

For more information about Melatonin, such as how it works and when it should be given, click here.

Mitotane

Mitotane is a chemotherapy drug that, for many years, veterinarians were prescribing off-label for the treatment of Cushing’s Disease in dogs. For the purpose of curing this condition, Mitotane would essentially destroy the outer layers of the adrenal gland, leading to some pretty severe side effects.

While some “old school” veterinarians may still believe in this medication as an effective treatment option, Mitotane is not currently recommended by the FDA or the AVMA and has the potential to cause serious, lasting harm to your pet’s body.

Surgical Treatment of Cushing’s Disease in Dogs

Though not as popular a treatment option as oral medication (likely due to cost), surgery is another available option for treating Cushing’s Disease in dogs. Surgical removal of an offending tumor can cure the body of Cushing’s syndrome, so long as the tumor itself is benign (non-cancerous).

There are two different ways to surgically remove a tumor from the adrenal glands: partial adrenalectomy (in which the tumor itself is removed while leaving the rest of the gland intact) or total adrenalectomy (in which the adrenal gland itself is removed entirely). The latter option is usually reserved for large tumors. Fortunately, while adrenal glands are an essential part of the body that a dog cannot go without, one adrenal gland can easily do the work of both if necessary.

Unfortunately, surgical removal of a pituitary-based tumor is much more complex and is not currently offered in veterinary medicine. Instead, radiation therapy may be an appropriate option for shrinking these types of tumors.

Lifestyle Changes for Cushing’s Disease in Dogs

In addition to daily medication, there are several simple lifestyle changes that an owner can make to improve the overall health and well-being of their four-legged companions, starting with their diet.

One of the most common questions that owners ask is, “is there a specific diet dogs with Cushing’s Disease should follow?”

While there is no specific prescription food or homemade diet that’s best for dogs with Cushing’s, there are certain dietary changes that you can make to help your pup feel healthier and stronger as a whole.

For instance, one of the most common symptoms of this condition is excessive weight gain. To combat this at home, consider feeding your dog a diet that is low in fat and high in protein.

Additionally, dogs with Cushing’s may develop noticeable muscle wasting over time. To help them build up stronger muscles and healthier bones, make sure their daily diet is chock-full of vitamins and minerals.

Another great way to keep your dog healthy while he’s undergoing treatment for this condition is to increase his daily exercise. Doing so will help your pup combat weight gain while simultaneously keeping his muscles nice and strong.

It’s also important, during this time, to ensure that your dog’s environment is as peaceful and stress-free as possible. With the body producing too much of the stress hormone already, the last thing we want to do is increase stress at home!

FAQs About Cushing’s Disease in Dogs

“Is my dog in pain with Cushing’s Disease?”

Cushing’s Disease is not an inherently painful condition, though it may cause your pup to experience some uncomfortable symptoms such as recurrent urinary tract infections (UTIs), excessive weight gain, or skin-related issues such as acne, pustules, or sores. This is especially true for pets who have not yet been diagnosed or when the disease itself is not controlled.

“Why does my dog lick things obsessively?”

While there aren’t (yet) any relevant studies available to help answer this question, there are several reasons why a dog with Cushing’s Disease may lick excessively. For one, Cushing’s can cause severe skin irritation, including hair loss, redness, and itchiness, along with the development of acne, pustules, or sores. If your dog has irritated skin as a result of his condition, he may be licking himself excessively in an attempt to self-soothe or satisfy the “itch.”

Another common symptom of Cushing’s is increased thirst. If your pup has this symptom but does not have access to water, he may lick obsessively in an attempt to remove the dry feeling from his mouth.

“What is the life expectancy of a dog with Cushing’s Disease?”

This question can be a tricky one to answer as life expectancy, in general, will be different for every dog - while some only live to eight or nine years of age, others will live to be eighteen or twenty! And because this condition primarily affects senior dogs, it can be difficult to determine the correlation between Cushing’s and life expectancy.

Say, for instance, that a senior dog passes only two short years after being diagnosed with Cushing’s Disease - is this a result of the disease itself, or would he have passed at that time regardless due to his own genetics? It’s impossible to say for certain.

While on the surface this condition doesn’t seem to have an obvious impact on a dog’s life expectancy, the comorbidities of this disease, when left untreated, may tell a different story.

“Is it OK to walk a dog with Cushing’s Disease?”

Absolutely! Not only is it okay to walk a dog with Cushing’s Disease - it’s encouraged! Cushing’s has the potential to cause a wide array of symptoms that can be reduced by frequent exercise, such as weight gain. There are so many benefits to exercising your dog regularly - not only will it keep your pup active, but it will also help him feel stronger in the long run.

“How can I prevent Cushing’s Disease in dogs?”

Unfortunately, Cushing’s Disease can not be prevented if it develops naturally. Pituitary and adrenal gland tumors, which are the two main causes of Cushing’s in dogs, form spontaneously and cannot be stimulated (or reduced) by any outside factor. The best thing that any loving pet parent can do in this situation is to manage the disease to the best of their ability under the guidance of a trusted veterinarian.

However, it is possible to prevent your dog from developing Iatrogenic Cushing’s Disease by simply avoiding the long-term use of steroid medications.

“What are the final stages of Cushing’s Disease in dogs?”

In most cases, Cushing’s Disease is a very manageable condition. However, there may come a time when the disease takes a toll on your dog’s body that is too great to bear. And though the signs of Cushing’s itself are often very subtle, symptoms that develop during the final stages of a dog’s journey are not.

These symptoms may include:

• Little or no response to medication, even at the highest possible dose
• Neurological abnormalities (such as sudden aggression, disorientation, circling, or even seizures)
• Frequent skin or urinary infections that are no longer responsive to previously successful treatments or medications
• Extreme lethargy that causes a loss of interest in previously enjoyable activities (such as playing fetch in the yard or devouring a favorite treat)

If your dog begins to show any of these symptoms, it’s important to talk to your veterinarian and have an open discussion about your dog’s true quality of life.

“What is the prognosis for a dog with Cushing’s Disease?”

In most cases, the prognosis for a dog with Cushing’s Disease is excellent, especially for those that are diagnosed prior to the onset of more serious complications. Under the care of an experienced veterinarian, most dogs can be effectively managed for many years following their diagnosis.

Conclusion

Cushing’s Disease is a complicated endocrine disorder that affects nearly 1 in 200 dogs. Though not a painful condition, it does have the potential to cause a wide array of uncomfortable symptoms, including skin irritation, weight gain, and frequently recurring urinary tract infections. The good news is that, with proper management, most dogs with Cushing’s Disease will live comfortably well into their senior years.