A Comprehensive Guide on Diagnosis and Treatment of Cushing’s disease in Dogs 

Your 8-year old dog has been drinking a lot more water lately and is eating everything in its sight. He is losing hair and he has developed a potbelly. Not able to identify what is wrong with him? Visiting a vet and some diagnostic tests can confirm whether your pet has hyperadrenocorticism which is commonly referred to as Cushing’s disease.

Cushing’s disease results due to the overproduction of the cortisol hormone. It is produced and stored by the adrenals that are two small glands present on top of the kidneys. This condition occurs not just in dogs but also in horses, cats, and humans as well. However, it is more commonly diagnosed in dogs.    

Cortisol is one of the natural body steroids that helps the body to adapt quickly during times of stress. It also helps the body to regulate weight, skin condition, tissue structure, and other features necessary for maintaining good health. Too much cortisol release can weaken the immune system thereby leaving the body vulnerable to infections and diseases. This is the reason why you need to rush to a vet immediately if you are noticing any symptoms of the condition in your beloved pooch. 

• • • • • • • • Common kinds of Cushing’s disease 
                1. Pituitary dependent
                2. Adrenal Dependent
              • Breeds in which Cushing’s disease is commonly observed
              • How does Cushing’s disease affect dogs?
              • What are the common symptoms of Cushing’s disease?
              • What tests would a veterinarian prescribe for diagnosing the condition?
              • Treatment of Cushing’s Disease
              • Side effects due to drug treatment
              • What to expect after the treatment has commenced?

Common kinds of Cushing’s disease

Although the symptoms and diagnosis remain the same, the treatment of the condition may vary based on the kind of Cushing’s disease your beloved pet is dealing with.

Pituitary dependent

The pituitary gland makes several hormones including adrenocorticotropic hormone. Any tumor in the gland can result in the overproduction of this hormone. It can enter the bloodstream and reach adrenal glands thereby overstimulating them to produce more cortisol than what is required by the body. Though pituitary tumors can be removed from humans, it is not a common practice to remove them surgically in dogs. More often, the condition is treated with medications for maintaining optimum cortisol levels.   

Adrenal Dependent 

Most of the Cushing’s syndrome observed in dogs is either pituitary or adrenal dependent. About 80-80 percent is due to pituitary gland overstimulation. In the rest 15-20 percent, it is due to a tumor on the adrenal glands that stimulate excess production of cortisol.  

This form of Cushing’s disease is less common. It can be treated only with surgery for removing the tumor present in the adrenal glands. Benign tumors can be cured with surgery but the process is quite complicated.  

No matter what the condition is, it is crucial that you take your pet to a vet for a proper diagnosis and discuss the options available. The kind of Cushing’s disease will actually determine what would be the preferred line of treatment. Generally, a blood test is enough to diagnose where the condition is pituitary or adrenal dependent. An ultrasound may also help in detecting the tumor on the adrenal gland.

Breeds in which Cushing’s disease is commonly observed

Large dog breeds generally develop adrenal tumors. Here are some breeds that are commonly diagnosed with the condition. 

• Boxers 
• Dachshunds 
• Boston terriers 
• Poodles 
• Staffordshire terriers 
• Yorkshire terriers

How does Cushing’s disease affect dogs?

Whenever a dog is stressed, its body releases cortisol hormone to guide it to work quickly to fight off the cause of stress. It is more of a flight or fight situation where a quick reaction is required. A dog’s body reacts to this by speeding up its metabolism and releasing energy in the form of sugar and fat while holding on to water. This is a healthy natural response to any stressful situation in a healthy dog.    

Each time cortisol is produced in a dog, its body will react by releasing sufficient energy to overcome the cause of stress. Dogs with Cushing’s disease have too much cortisol being produced. This can make a dog prone to various health conditions in the long term. It could make the dog prone to diabetes, infections, and skin changes. 

You obviously would not want your beloved dog to go through all this and hence you should consult a trusted vet immediately.  

What are the common symptoms of Cushing’s disease?

Overproduction of cortisol results in several symptoms in dogs. Being aware of the common symptoms will ensure that your pooch receives proper diagnosis and treatment at the right time.  

The condition generally occurs in older dogs and the disease develops and progresses slowly.  Some of the most prominent ones that have been observed have been listed below. 

• Increase in appetite 
• Pot-bellied appearance 
• Hair loss 
• Increased drinking and urination
• Reduced activity
• Thin or fragile skin 
• Excessive panting 
• Recurrent skin infections 

Hair loss due to Cushing’s disease primarily occurs on the body sparing the legs and head. The skin is not itchy as it is with other skin conditions. If you lift the fold of skin on your pet with Cushing’s disease, you will note that the skin is thinner than normal. The pet may also have fragile blood vessels and hence can bruise quite easily.  

As cortisol controls numerous functions in several organs within the body, the signs of the disease may not be the same. If left untreated, then pituitary tumors can grow large enough to press on the brain and result in neurological symptoms such as difficulty in seeing and walking. Seizures and diabetes are also noted in dogs suffering from the condition. 

If you have administered your pet prednisone or any other similar drug, then they may develop signs that might look like Cushing’s disease but it would not be the case. Speak to your local veterinarian to confirm what is triggering the symptoms.  

What tests would a veterinarian prescribe for diagnosing the condition?

There is no single test that can help diagnose Cushing’s disease. The history, physical exam, and results of initial urine and blood tests can help in identifying the presence of Cushing’s disease. Also, an increase in the platelet and white blood cell count can result in an increase in the liver enzyme called Alkaline Phosphatase (ALP), increased cholesterol, and increased blood sugar.  

Here are some of the common tests prescribed for confirming Cushing’s disease. 

• Urine cortisol/creatinine ratio

A urine cortisol test is a primary screening test for Cushing’s. It can be conducted without having to take your dog to the vet clinic. If your pooch tests positive, then further screening may be needed.    

• ACTH stimulation test

Generally, a blood sample is taken from the dog and then a small dose of synthetic ACTH hormone is injected into the dog. Another blood sample is collected an hour later. Cortisol level values obtained help in the diagnosis of the condition.   

• Low dose dexamethasone suppression test

This test is performed for over 8 hours. Blood samples are drawn at 0, 4 and 8 hours after the dog receives a small dose of synthetic steroid dexamethasone. The cortisol levels are then measured to confirm the condition. High dose dexamethasone suppression tests can also be prescribed by the vet after a thorough examination. 

• Ultrasound 

Dogs with Cushing’s disease generally have an enlarged adrenal gland or liver. Both conditions can be noted if the dog has pituitary-dependent condition. Your vet may also prescribe ultrasound or x-rays for checking the glands. 

Adrenal glands cannot always be examined with an ultrasound examination. In some pets, an adrenal tumor can be diagnosed by observing the growth into large blood vessels that are present closer to the gland. The tumor spread from the liver can also be detected.

• Test for urinary infection 

As large amounts of cortisol hormone released in the body can suppress the entire immune system, dogs with Cushing’s disease are more prone to bacterial infections. Especially, you will notice an increase in bladder infection in such dogs. A culture of urine can help in diagnosing the infection.  

Treatment of Cushing’s Disease

Most veterinarians treat both pituitary and adrenal dependent Cushing’s disease with appropriate medication. The only way to cure it is by removing the adrenal tumor if the condition is adrenal-dependent and if the tumor has not spread into the surrounding region yet. However, as surgery can result in complications in senior dogs, most cases are treated just with medications. Surgical techniques for removing pituitary gland tumors are still being studied. However, it is not a widely available option.  

Treatment for pituitary-dependent Cushing’s disease generally involves the use of oral medications for treating clinical signs of excessive urination, increased drinking or appetite, and changes in the skin. No direct treatment is done for removing the tumor. Furthermore, your vet can also opt for radiation therapy for treating the condition. 

Although Cushing’s disease is a condition that can last lifelong, you can manage the disease with medications prescribed by your vet. It is also essential to take your dog for vet visits regularly. Frequent blood tests may also be needed in the process. Monitoring blood tests help in tracking the response being exhibited by your pet towards the treatment and dosage. Adjustments can be made in the dosage for better results.  

You have to make frequent veterinary check ups during the first few months after starting the treatment. Once the dog’s response and tolerance are understood, then the frequency of visits would come down. 

Vetoryl is the only drug approved by the FDA for treating both pituitary and adrenal dependent Cushing’s disease in dogs. This prescription drug stops the overstimulation of cortisol. It can never be prescribed for a dog that  

• Is pregnant 
• Has both live and kidney disease 
• Is already on medications for the treatment of heart disease 

Side effects due to drug treatment

The most common side effects noted in dogs on medications for the treatment of Cushing’s disease are

• Weakness 
• Diarrhea
• Lack of energy 
• Vomiting
• Reduced appetite

There can be serious side effects occasionally. 

• Collapse 
• Severe potassium/sodium imbalance 
• Bloody diarrhea

Anipryl is another drug approved by the FDA for treating Cushing’s disease in dogs. However, it can be used only for the treatment of the uncomplicated pituitary-dependent condition. The human chemotherapy drug, Lysodren has also been used by vets for treating the condition in dogs. Lysodren removes the layers of the adrenal gland that are responsible for the production of cortisol. However, this can be done only under careful supervision and may result in severe side effects.  

Treatment of Cushing’s disease is more of a balancing act. Most dogs with this condition can live a good, long life if they are monitored closely by both the owner and the veterinarian. You can help your beloved dog get over and lead a normal life if you are ready to give them that extra care, love, and treatment from a qualified vet.    

What to expect after the treatment has commenced?

Once your vet has prescribed medications for your pet, you will start noticing improvements in the symptoms that you earlier observed in them. These medications have to be given lifelong if you want to improve the quality of life of your pet. Your vet may change the dosage and medications over time. However, this will be with careful monitoring over a period of time. 

Usually, a blood test is performed to check if your dog is receiving the most accurate dosage. Initially, it is evaluated within two weeks of starting the therapy. Once the right dosage has been identified, the ACTH stimulation test will be done once in three to four months. 

You need to alert your vet if you notice any clinical signs in your dog that your vet would have already informed you before starting the course of treatment. Weakness, decreased drinking, changes in appetite, diarrhea, decreased activity, and increased sleeping can be the warning signs. Inform your vet immediately if you notice these signs. 

Cushing’s disease can only be managed and cannot be cured. If your dog with Cushing’s disease is not just the only pet you have, then you will have to train other dogs to be gentle with their buddy (Robyn Achey, 2006).  With little care, your dog can live a quality life for years. The sooner you start the treatment, the sooner your pet will feel better.

References

1. Hershey T.,  (2019). My dog has an elevated alkaline phosphatase. What does that mean?. Southwest Journal https://www.southwestjournal.com/voices/ask-the-veterinarian/2019/04/my-dog-has-an-elevated-alkaline-phosphatase-what-does-that-mean/ 
2. Rattner F., (2015). Ask a Vet: Multiple tests required for Cushing’s disease diagnosis.  Capital Gazzete https://www.capitalgazette.com/lifestyles/ph-ac-cl-vet-0421-20150421-story.html
3. Sanders, Karin & Kooistra, Hans & Galac, Sara. (2018). Treating canine Cushing’s syndrome: Current options and future prospects. The Veterinary Journal. 241. https://www.researchgate.net/publication/327910975_Treating_canine_Cushing’s_syndrome_Current_options_and_future_prospects
4. Mark E. Peterson, Medical Treatment of Canine Pituitary-Dependent Hyperadrenocorticism (Cushing’s Disease), Veterinary Clinics of North America: Small Animal Practice,Volume 31, Issue 5, 2001, Pages 1005-1014, ISSN 0195-5616, https://www.sciencedirect.com/science/article/abs/pii/S0195561601500108
5. American Veterinary Medical Association. (2009). FDA providing guidance on use of drug for Cushing disease. AVMA website.  https://www.avma.org/javma-news/2009-10-15/fda-providing-guidance-use-drug-cushing-disease
6. Robyn Achey, B. G. (2006). In 1000 Best Dog Training Secrets . Sourcebooks Inc.