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

Have you been worrying about your dog’s health and well-being lately? Has he or she been exhibiting symptoms such as an increase in appetite or thirst, urinating more frequently, hair loss, thin hair, weight gain, or low energy levels? These are some of the symptoms that can indicate Cushing’s disease in dogs. It is important to bear in mind that not all symptoms will become apparent in all canine patients. In fact, many of the signs of Cushing’s disease in dogs could be associated with a host of other diseases as well. To determine if your dog has Cushing’s disease, your veterinarian will to look at the symptoms and compare them to several different diagnostic test results to arrive at the diagnosis. Read on to learn more about the history, symptoms, diagnosis, treatments, and more about Cushing’s disease in dogs.

History of Cushing’s Disease

Before we get into causes, symptoms, diagnosis, and treatments of Cushing’s disease in dogs, let’s first explore a little basic history on the subject. Cushing’s disease was originally diagnosed in humans and later found in dogs and other animals.

1912 – Dr. Harvey Cushing

Cushing’s disease itself is associated with increased cortisol secretion and was first described in 1912 by its namesake, Dr. Harvey Cushing, who was an American neurosurgeon. He was, at that time, presented with a very unique case of this particular disease when a 23-year-old woman complained of symptoms including abnormal hair growth, amenorrhea, cerebral tension, hydrocephalus, and painful obesity.

Report Published in 1932

That particular combination of symptoms as a medical disorder had never been described by anyone at the time. Dr. Cushing was quite confident that those symptoms were caused by a pituitary gland dysfunction. They also bore an uncanny resemblance to the symptoms associated with adrenal tumors. Based on that conviction, and Dr. Cushing’s in-depth knowledge of anterior pituitary cell types, he hypothesized that a pituitary disorder could explain the combination of symptoms. After numerous case reports and experimental evidence had been compiled, Dr. Cushing published a report on the subject of pituitary basophilism being the actual cause of Cushing’s disease in 1932.

What Causes Cushing’s Disease in Dogs?

Cushing’s Disease in Dogs

Cushing’s disease is caused by an overproduction of the hormone cortisol, by the adrenal glands. Also known as hyperadrenocorticism, Cushing’s disease is either adrenal-dependent, pituitary-dependent, or caused by prolonged or overuse of corticosteroid medications. The adrenal gland produce an excess of cortisol which is a steroid and has steroid like side effects on the body. 

Cortisol

One of the hormones secreted by the endocrine system is cortisol. When cortisol levels are normal, it can perform a number of quite useful functions, which includes helping your dog to respond to stress while modulating his or her immune system. On the other hand, too much cortisol in your dog’s body can result in a lot of damage. 

A Natural Steroid

According to a veterinarian in FDA’s Center for Veterinary Medicine, Ann Stohlman V.M.D., cortisol is a natural steroid in the body and a normal amount helps the body when it needs to adapt during times of stress. It also helps with regulating proper body weight, skin condition, tissue structure, and other good health features. However, excess production of cortisol results in a weakened immune system and it leaves the body vulnerable to other infections and diseases.

Fluctuating Cortisol Levels

In healthy dogs, the cortisol levels fluctuate constantly for the express purpose of keeping their systems in balance. It usually helps their bodies with responding to stress, and it also has an effect on many of the normal functions of your dog’s body. Those functions include regulating blood sugar levels, immune system responses, skeletal muscles, and much more. Cortisol secretions usually occur because of:

• Infections
• Pain
• Stress
• Temperature fluctuations
• Trauma

Fight or Flight

Cushing’s disease is a condition where your dog’s body produces excess amounts of cortisol, which is the stress hormone. The two small adrenal glands above his kidneys produce this hormone. During times of stress, those adrenal glands start releasing the cortisol.

It’s also well-known for being the “fight-or-flight” hormone. It’s actually is a healthy survival mechanism that’s been serving animals well for a long time when they’re faced with any kind of a dangerous situation while living in the wild. However, when a dog is plagued by chronic stress, the cortisol gets released in amounts that are excessive and that can strike a devastating blow to your dog’s health.

Pituitary-Dependent

The pituitary gland is a pea-sized gland located at the base of the brain and it makes several hormones, which includes adrenocorticotropic hormone (ACTH). A pituitary tumor will cause ACTH overproduction, which then travels to the adrenal glands via the bloodstream, stimulating them so that they produce more cortisol than needed by the body. 

The most common cause of Cushing’s disease in dogs is a benign pituitary tumor, which is a non-spreading tumor. In rare cases, a pituitary tumor could be malignant. Approximately 80–85 percent of cases are pituitary-dependent. The condition is described as pituitary-dependent hyperadrenocorticism (PDH) if the disease develops due to pituitary gland problems. That means that they’re triggered by a pituitary gland tumor.

Adrenal-Dependent

Adrenal gland tumors have been found to be responsible for the remaining 15 to 20 percent of cases (adrenal-dependent hyperadrenocorticism/ADH). Although not as common, a tumor that is producing corticosteroid could grow on either one or both of the adrenal glands. Adrenal tumors have a 50/50 chance of being either malignant or benign. Your veterinarian might use an ultrasound to help with detecting an adrenal gland tumor. The tumor, whether benign or malignant, will release hormones that are continuously stimulating the dog’s adrenal glands corticosteroid production. 

Corticosteroid Medications

Excessively administering high-doses or long-term corticosteroid medications are also a common cause of canine hyperadrenocorticism. These medications are commonly used for treating certain types of cancer, immune disorders, and allergies, as well as to reduce inflammation, or simply as a replacement therapy for abnormally low cortisone levels. What is known as Iatrogenic Cushing’s disease can be reversed by reducing the medication or stopping it completely.

Description of Common Symptoms

Cushing’s disease is most commonly found in middle-aged to older dogs – about 7-12 years old. Some common breeds include Dachshunds, Poodles, Boxers, Boston terriers, Yorkshire terriers, and other terrier breeds. 

Symptom #1: Increased Thirst (polydipsia) & Excessive Urination (polyuria)

If you find the need to consistently replace the water in your dog’s bowl and it seems like he’s urinating or even having more incontinence issues than usual, it could be time to check for other signs that could possibly point to Cushing’s disease in dogs. Polydipsia is drinking more water than normal which results in polyuria, which is urinating more than normal. Because the urine is more dilute than normal, this can result in an increased incidence of urinary tract infections. 

Symptom #2: Increase in Appetite (polyphagia)

Dogs with Cushing’s disease often uncommonly hungry. They usually want to eat bigger meals, more treats, and more frequently. Your dog could also start suffering from what is commonly known as “dietary indiscretion”. What that means is that he might try to eat stuff that he shouldn’t and normally wouldn’t, such as feces, dirt, rocks, grass, wood, or even metal. It’s up to you to stop him from doing any of that since it could obviously be quite harmful.

Symptom #3: Weight Gain

The polyphagia mentioned above can result in weight gain. When cortisol levels rise, they can cause an increase in appetite in a dog who has Cushing’s disease. A bigger appetite paired with increased fluid retention can cause unnatural weight gain. If your dog starts looking like he has a potbelly appearance, but at the same time, muscle shrinkage in his legs, then you should take him to the vet as soon as possible. Although it might not even turn out to be Cushing’s, it could be some other disease that may also be serious.

Symptom #4: Hind Leg Weakness & muscle loss

A dog with Cushing’s disease can experience some level of muscular atrophy in his hind legs. This can decrease his hind leg function and movement. In this case, your veterinarian might recommend supplements for joint support or changing the diet. 

Symptom #5: Personality Changes and Lethargy

A change in personality can be a very sad symptom of Cushing’s disease in dogs. Many pet parents have reported that their dog just isn’t acting like themselves. They might also say that their dog has lower energy levels, or is acting lethargic. Either of these symptoms could be a sign of Cushing’s disease, and visiting your vet visit is highly recommended.

Symptom #6: Sparse Hair/Hair Loss

Although hair loss can be attributed to a number of different issues, hair loss, or thinning hair that is symmetrical (i.e. occurring on both sides of your dog’s body) can be a key indicator of Cushing’s disease in dogs. It’s also a good idea to start watching for skin sensitivity on his flanks or his trunk.

Other Symptoms Include…

• Pot-bellied abdomen
• Bruising
• Skin infections
• Fat pads on shoulders and neck
• Increased panting
• Infertility
• Nocturnal urination (nighttime accidents)
• Scaly patches on elbows and skin
• Skin darkening
• Thin skin

What your Veterinarian Is Looking For

When you take your dog to the veterinarian for any of the above mentioned symptoms, your vet will likely recommend a few different tests to check for the following abnormalities. 

1. Blood Clots: This often manifests as an increased platelet level and can lead to abnormal clotting in the blood. 
2. High Alkaline Phosphatase Levels: This is one of the most common abnormalities on the bloodwork of a dog with Cushing’s disease. The alkaline phosphatase is a liver enzyme and is often the result of the increase in cortisol levels and higher blood sugar levels.
3. Increased other liver enzymes: Other liver enzymes such as the ALT (alanine aminotransferase), and AST (aspartate aminotransferase) can also be elevated.
4. Multiple Symptoms:  When dogs exhibit a number of Cushing’s warning signs, there’s a high possibility that they have Cushing’s Disease.
5. Increase in Cortisol Levels: This symptom is, of course, the most reliable Cushing’s disease indicator and can almost always either prove or disprove the presence of Cushing’s in a diagnosis.
6. Increase in Sex Hormones: Atypical Cushing’s disease can show normal cortisol levels, however, the sex steroids (i.e. aldosterone, estradiol, and progesterone) levels may be elevated.

Diagnosis of Cushing’s Disease Dogs

Recognize the Signs

Your first step to ensure that your dog receives appropriate care is recognizing the early signs. Now that you know what is Cushing’s disease in dogs, you can look out for the symptoms and take your dog to the vet if there is anything that appears abnormal.

For diagnosing Cushing’s disease in dogs, your veterinarian will first be taking your dog’s comprehensive health history. Then they will be performing a complete physical exam along with some basic lab work such as a complete blood cell count, blood chemistry profile, urinalysis, and fecal examination. If Cushing’s disease is suspected as the most likely cause of the symptoms your dog is experiencing, there will be more tests aimed at definitively diagnosing the condition.

Diagnostic Tests

Here are some of the tests that could be administered in order for your vet to reach a diagnosis:

LDDST

The low-dose dexamethasone suppression test is the test of choice for the screening of Cushing’s disease in dogs. It requires taking a blood sample for the purpose of measuring your dog’s baseline cortisol level. Then, your dog will receive an injection of a small amount of dexamethasone, which is a steroid. His blood cortisol levels will then require measuring at four and eight hours following the injection. In normal dogs, the injection will inhibit the secretion of cortisol. In dogs who have Cushing’s disease, the cortisol will not be suppressed, and instead will be in high levels in the blood stream.

ACTH Stimulation Test

This is another blood test to help in the diagnosis of Cushing’s. It is also used to diagnose the opposite of Cushing’s which is Addison’s disease or hypoadrenocorticism. In this test, a baseline blood sample is collected, then a stimulating hormone is given which stimulates cortisol production. An hour later, another blood sample is taken to see if the stimulating hormone actually stimulated cortisol production. 

Urine Cortisol: Creatinine Ratio Test

Another test is the urine cortisol: creatinine ratio test. This test can be combined with the blood tests to help in diagnosis.

No One Definitive Diagnostic Test

Unfortunately, there isn’t any single diagnostic test that can be relied upon 100% for achieving a definitive diagnosis of Cushing’s disease in all of the cases. Your veterinarian might also need to perform an abdominal ultrasound, take radiographs (x-rays), or perform other tests to determine whether ADH or PDH is responsible for the disease and if the tumors are benign or malignant.

Treatment

In the event that your dog is diagnosed with Cushing’s disease, it’s important to remember that despite the fact that it’s not curable (except via expensive and risky adrenal gland or brain surgery), it is a highly managable disease. Proper care and treatment can help with managing the symptoms and improving your best friend’s quality of life. Cushing’s is a disease that is well-documented and has numerous treatment options. Plenty of research is available to aid the determination of the best treatment regimen for your dog.

Once you and your veterinarian have done thorough research and are in complete agreement regarding the optimum treatment option for your pet, you can proceed with the next steps.

Treatment of Cushing’s Disease

If your dog is exhibiting the signs of Cushing’s disease and your veterinarian has diagnosed it on various tests, they will discuss treatment with you. There are three treatment options fo Cushing’s disease: medical, surgical, and radiation therapy. 

For the most common, PDH form of Cushing’s disease, the most common method of treatment is medical, involving giving daily medications to inhibit steroid production. The most common medications used are Trilostane and Mitotane.

1.Trilostane Treatment (Vetoryl)

Following the decision to start treating your dog’s pituitary-dependent Cushing’s disease, your vet will probably prescribe Trilostane (Vetoryl). This drug that can have some serious side effects, so your dog should, of course, be closely monitored. Trilostane can interact with certain common medications, so be sure to have an in-depth discussion with your vet regarding all medications and supplements that your dog currently takes.

2. Lysodren: Traditional Therapy (aka Mitotane)

This drug works by limiting the adrenal gland’s activity. It is used also widely used for treating adrenal cancer. Many veterinarians are prescribing Lysodren for dogs with Cushing’s disease because of its unique effect on the proper functioning of the adrenal gland.

If your dog is undergoing medical treatment for Cushing’s disease, you should be prepared for continuing treatment for the rest of his life. You’ll also need to be vigilant about watching out for any adverse reactions to these powerful medications.

Typical adverse reaction signs can include:

• Lack of energy
• Weakness
• Lack of appetite
• Vomiting
• Diarrhea
• Difficulty walking

Contact Your Vet

Should your dog start suffering from any of those side effects, immediately contact your vet while also discontinuing the medication but only under the veterinarian’s supervision. Your vet will also want to schedule regular follow-ups for monitoring your dog for any adverse effects of the medication for Cushing’s disease and for ensuring that your dog is continuing to receive the proper dose. You should also take your dog to see your vet several times yearly after your dog reaches the maintenance phase of his therapy.

Drug monitoring with regular physical exams and bloodwork is required. Radiation therapy is another treatment option and has a high rate of response but can be expensive and dogs often still need medications.

Treatment for the less common, ADH form of Cushing’s, is best with surgical removal of the adrenal glands. Surgery can be risky and expensive and is usually best performed by a board certified veterinary surgeon. Medical management with Trilostane is another option.

Iatrogenic Cushing’s is treated by reducing or discontinuing any steroid medications.

The prognosis of medical therapy for PDH is about 2 years and 2-5 years with radiation therapy. The prognosis of ADH with surgery is about 18 months.

That All-Important Decision

Making the all-important decision about whether or not to start treating your dog’s Cushing’s disease, requires careful consideration of the symptoms. For example, if your dog is drinking excessively but isn’t urinating inside your house, it may not necessarily be a problem. However, if he suffers from recurring skin or bladder infections, urinary protein loss, high blood pressure, or gets so hungry that he’s always heading to the kitchen and begging for more food, then proper treatment is a must. Once he has been diagnosed as having Cushing’s Disease, you must decide to go with what treatment you feel most comfortable with.

Supplements and other support for Cushing’s Disease

The medications given to treat Cushing’s disease are helpful in controlling the steroid production and the adrenal glands. However, Cushing’s can have negative effects on the liver, urinary tract, and skin and supporting these systems is beneficial in the overall treatment of your dog with Cushing’s. Make sure to talk to your veterinarian before starting any supplements to make sure they are the right choice for your dog and that you give the right doses.

Lignans

Both flaxseed lignans and HMR lignans work equally well as a supplement choice for dogs with Cushing’s disease, however,  they’re derived from different natural sources. HMR Lignans are derived from the Norway spruce tree while flaxseed lignans are from flaxseed hulls. Flaxseed lignans contain fiber whereas HMR lignans do not. These are considered to be helpful in supporting dogs with Cushing’s because they are both capable of inhibiting the two enzymes necessary for producing cortisol. Lignans work in a similar manner as melatonin treatment, however, they do it by inhibiting different enzymes.

Lignan Benefits Include

1. The return of your dog’s normal weight and a healthy appetite
2. Restoration of your dog’s energy
3. Reduction in his cortisol levels via inhibition of the 3-beta HSD Enzyme as well as reducing the estradiol via inhibition of the aromatase enzymes
4. New hair growth

Important to Note

Note that you should not use flaxseed oil or whole flaxseed for treating your dog because they contain a very low lignan content can cause increased triglycerides.

Melatonin – Not Just For Sleeping

Melatonin is another effective supplement and helps by inhibiting the enzymes that are necessary for cortisol production. The inhibition of these enzymes reduces cortisol levels. It’s important to ensure that you’re using the correct kind of melatonin and that you are keeping melatonin at a constant level in your dog’s body. Some people have been thinking that melatonin is given to dogs who have Cushing’s just for helping them to sleep better. Although it may work that way in some cases, melatonin’s primary function is as an effective treatment option for reducing cortisol levels. This, in turn, helps with improved management of elevated stress hormones for dogs suffering from Cushing’s.

Herbal Medicine for Adrenal Support

It’s true that nature’s medicine cabinet contains many herbal remedies that can be effective in treating Cushing’s disease in dogs, including:

• Ashwagandha

Ashwagandha(Withania somnifera) is a supplement to help strengthen the body and improve overall health. It’s known to improve bodily response to environmental stressors and enhance immune function and energy levels. Studies have also shown that it has abilities to protect and support healthy liver function.

• Astragalus

Astragalus (Astragalus membranaceus) is a substance used for many centuries in the practice of Traditional Chinese Medicine. It is said to be responsible for imparting energy, strength, and vitality. It’s also considered to be a tonic adaptogen because regular use balances and strengthens the adrenal glands. It has traditionally been a big help with relieving cases of excessive thirst and frequent urination. Another added benefit of Astragalus use is the stimulation of the immune system.

• Burdock

Burdock(Arctium lappa) nourishes the liver. In Cushing’s disease, the liver can become overburdened. It is consumed as a vegetable for its blood-purifying properties and amazing nutritional value. In addition, it is also used for aiding in the relief of some skin disorder symptoms like dryness, scaliness, and irritation.

• Dandelion

Dandelion (Taraxacum officinale) has been traditionally used for nourishing the adrenal glands, kidneys, liver, and digestive tract. It’s actually a very gentle food-grade herb containing a very wide range of vitamins and minerals as well as sterols that are quite beneficial to the adrenal glands for encouraging healthy function. It also contains nutrients well-known for benefiting the healthy growth of hair and skin.

• Ginseng

Ginseng (Panax ginseng) is a substance used in Traditional Chinese Medicine for supporting good health. It’s also known as one of the best available adaptogenic herbs. Studies have shown its considerable benefits on the hypothalamic–pituitary–adrenal (HPA) axis. It has also been shown to aid in supporting healthy blood sugar and energy levels, muscle strength, and stamina.

• Horsetail

Horsetail (Equisetum arvense) offers a variety of minerals, including calcium, silica, sulfur, potassium, magnesium, and manganese. Horsetail’s diverse combination of minerals is known to benefit digestive health, hormonal balance, and the nervous system.

• Licorice

Licorice(Glycyrrhiza glabra) is an herb used in Traditional Chinese Medicine that offers a broad range of exceptional health benefits. Herbalists often prescribe licorice to help balance adrenal function in the presence of elevated cortisol levels. It also benefits the immune system, liver, and skin.

• Silica

Silica is a substance used in forming connective tissue, hair, and skin. Adequate amounts of silica can be responsible for ensuring a full coat of fur, as well as healthy skin.

Other Supplements for Helping Your Cushingoid Dog

When your dog has Cushing’s disease, the liver enzymes become elevated and the liver is overworked. Supplements that can help with supporting his liver can be a beneficial treatment option. These are supplements that you may have already heard of as being healthy supplements for human liver support. Consult your veterinarian for appropriate dosage.

• Milk Thistle

This is a natural compound used to help with liver problems. Veterinarians often prescribe Denamarin for dogs. It’s a blend of SAMe and milk thistle. 

• SAMe (S-Adenosyl L-Methionine)

This is another substance that is naturally occurring in the body. It is produced in a dog’s liver for normal liver function. It is used up very quickly in an overworked liver. In Cushingoid dogs, the liver becomes over-stressed when it is trying to handle the excess cortisol. Supplementing with SAMe can be extremely helpful.

• Joint Support

Joint support supplements could be recommended if your Cushingoid dog is suffering from hind leg weakness. When dogs have Cushing’s disease, they could be experiencing muscular atrophy in their hind legs. This often results in a reduction in the overall functioning of their hind legs. Veterinarians often recommend glucosamine or a glucosamine alternative for promoting joint stability and health.

Cushing’s Disease Diet for Dogs

You should pay special attention to your dog’s diet if they have been diagnosed with Cushing’s disease. A balanced diet is important but there are other important factors such as: 

• High protein
• Low fat
• Low in purines (found in organ meat)
• Low in carbohydrates
• Rich in Lignans

Consult your veterinarian for the best diet for your dog.

Untreated Cushing’s Disease in Dogs

Left untreated, Cushing’s can lead to other problems such as diabetes, heart disease, kidney failure, pancreatitis, and seizures as well as some other disorders. The Cushing’s symptoms are often chalked up to a dog’s natural aging process. A bloated belly, a bony appearance in his head, muscle weakness, or skin hyperpigmentation may be noticed. These are all possible signs of the disease and they should not be ignored or simply attributed to the “symptoms of old age”.

Is it Always Fatal?

No, not always. It is definitely a chronic illness, no doubt about it, and Cushing’s disease in dogs can have a very rapid and certainly severe effect on your pup’s overall quality of life unless it is treated properly. It can also result in a wide range of more serious health problems, which in some cases, can bring on fatal complications. However, being able to understand both the causes, symptoms, and treatment options for the disease could literally end up saving your dog’s life.

Life Expectancy

Cushing’s Disease in Dogs Prognosis

In the majority of cases, Cushing’s disease mainly affects older dogs. If the disease is correctly diagnosed at the early stage, and the appropriate treatments are administered, those senior canines can have a normal life expectancy. Treatment should include appropriate supplements and prescription meds from your vet if applicable.

How Long Does a Dog Live with Cushing’s Disease?

Questions that loving pet parents often ask usually include, “My dog has Cushing’s disease how long will she live?”, as well as, “How do I know when to put a dog down with Cushing’s disease?”, and, “How high is the percentage of dog Cushing’s disease deaths among senior dogs? What about younger dogs?” These are all good questions but unfortunately, they can only be answered definitively by your veterinarian.

Asking them is the first step. Don’t just imagine the worst. Get an expert veterinary opinion to put you at ease or prepare you for what is to come for you and your dog. Most importantly, never give up. Remember, there are new treatments coming to light every single day and one of them could help your beloved pooch.

Keep checking back with your vet. Don’t be afraid to mention a new treatment that you may have heard or read about. After all, your dog’s life could depend upon being on top of the latest developments in treating Cushing’s disease in dogs.    

The Ongoing Health of Your Dog

When choosing a Cushing’s disease therapy for your dog, you should take into account a number of things. These include cost, dosing schedule, efficacy, monitoring schedule, and possible side effects. If, after reading this, you have further questions and concerns about your dog’s ongoing health, be sure to consult your veterinarian for selecting a viable treatment option.