Cushing's Disease in Dogs - Symptoms, Diagnosis & Treatments

So What Exactly Is Cushing's Disease in Dogs?

“It’s widely thought that Cushing’s Disease tends to afflict middle-aged and older dogs however, increased levels of steroids (including medications) may also bring on similar symptoms.”

Cushing's Disease in Dogs 

Essentially, Cushing’s Disease is a type of endocrine disorder that affects dogs. Dogs have an endocrine system which is a series of glands throughout the body which release various hormones, one of the hormones that is released is cortisol. In itself, cortisol is an essential hormone which regulates a variety of functions in the dog’s body including body weight, stress response and blood sugar level control, however excess amounts can be problematic. 

The medical name for Cushing’s Disease is hyperadrenocorticism and it’s a popular type of endocrine disorder that affects dogs.

It’s widely thought that Cushing’s Disease tends to afflict middle-aged and older dogs however, increased levels of steroids (including medications) may also bring on similar symptoms.

Many animals can get this condition. People can get it too.

In general, there are 2 main variations that tend to affect dogs which are:

  • Pituitary dependent. This variation is the most common type of Cushing’s disease and it’s estimated that it affects between 80%-90% of dogs that do have Cushing’s. The pituitary dependent type of Cushing’s is when there is a growth or tumor around the pituitary.  These tumors tends to be benign (non-spreading) pituitary tumor and it’s fairly uncommon for them to find pituitary tumors that are malignant
  • Adrenal dependent. Another potential type of Cushing’s is adrenal dependent and this form is due to a tumor growth around the kidney area, on the adrenal glands. It’s estimated that 15%-20% of dogs with Cushing’s have this type.

Latrogenic Cushing's syndrome – this is a type of induced Cushing’s that tends to appear in dogs that have received steroid treatments over an extended period of time. This may include drugs that can be administered to reduce symptoms of allergies, immune disorders and even certain kinds of cancer in order to minimize the levels of inflammation.

This type of Cushing’s disease for dogs can be resolved by simply reducing or stopping altogether the relevant steroid treatment.

Symptoms of Cushing's Disease in Dogs

“Many of the symptoms of Cushing’s Disease in dogs are the same symptoms of other illnesses and health issues as well, making diagnosis more complicated.”

Symptoms of Cushing's Disease in Dogs

Symptoms may be difficult to detect and therefore it’s important to carefully observe your pet for any new types of behavior that can’t be explained due to external circumstances. To make things even more complicated, many of the symptoms of Cushing’s Disease in dogs are the same symptoms of other illnesses and health issues as well, making diagnosis more complicated.

Keep in mind that Cushing’s Disease in dogs tends to affect middle-aged and older dogs so it’s important to be aware of the symptoms for dogs that have reached those age groups. Not all dogs will exhibit all symptoms.

Here are some common symptoms associated with Cushing’s disease in dogs:

  • Increased thirst and urination (polydipsia and polyuria, respectively)
  • Urinating at night or having accidents
  • Increased hunger
  • Increased panting
  • Pot-bellied abdomen
  • Obesity
  • Fat pads on the neck and shoulders
  • Loss of hair and slow regrowth of hair
  • General lethargy & lack of energy
  • Muscle weakness
  • Infertility
  • Darkening of the skin
  • Thin skin
  • Bruising
  • Hard, white scaly patches on the skin, elbows, etc. (associated with the disease calcinosis cutis) 
  • Excessive panting

Diagnosis of Cushing’s Disease in Dogs

“To reach a clear and accurate diagnosis, your vet will need to perform a series of exams and tests to disqualify other potential causes.”

Diagnosing Cushing's Disease in Dogs

The first step in determining if your dog has Cushing’s disease is to first understand your dog’s medical history. Following that, your vet will most likely carry out a physical exam. The next step would be to perform various blood tests to ensure that your dog’s blood cell count is within the normal range and additional fecal exam and possible a urinalysis to determine any additional potential medical conditions besides Cushing’s that could be the cause of the symptoms.

Going forward, should your vet believe that the culprit is Cushing’s disease for dogs, they may want to perform a urine cortisol to creatine ratio. This examination may help to identify a urinary tract infection or other protein issues that are frequently found in the liver and bones known as alkaline phosphatase. These are all possible symptoms of Cushing’s disease in dogs. If the results do in fact indicate positive signs for Cushing’s disease in dog, your vet will most likely proceed to carry out additional exams. 

  • ACTH stimulation test. It measures how well the adrenal glands work in response to a hormone called ACTH that usually prompts them to make cortisol. The vet will take blood samples before and after your dog gets a shot of ACTH to see how the hormone affected him.
  • Low dose dexamethasone suppression (LDDS) test looks at how your dog’s body works with a man-made version of cortisol, called dexamethasone. Blood samples before and after he gets a shot of the hormone help the vet see what’s going on.

If it seems like your dog may in fact be suffering from Cushing’s disease, your vet might want to do an ultrasound scan of his belly. This imaging test will help her see if there’s a tumor on the adrenal glands. That could affect the kind of treatment he needs.

 If the results do indicate that your dog has a high cortisol to creatine ratio, this could be an indication that they have Cushing’s disease but further testing may be required.

Another popular test to check if it really is Cushing’s disease in dogs is to carry out an exam called low-dose dexamethasone suppression test (LDDST). Tis test is involves taking a small blood sample in order to establish the dog’s standard cortisone level and following that, a minute quantity of dexamethasone is injected into the dog. Period cortisone level exams are then carried out to evaluate the level of cortisone secreted by the dog. Generally speaking, the cortisone level is checked after four to eight hours following the dexamethasone injection.

In a healthy dog, that dexamethasone injection should inhibit the hormone which stimulates the secretion of cortisol, thereby causing a reduction in the levels of cortisone in the dog’s body.

However, if your dog does have Cushing’s disease, the cortisone secretions will not be suppressed.

At the end of the day, there is no 1 exam that indicates with Cushing’s disease for dogs with full certainty and therefore your vet will carry out multiple tests in order to eliminate other potential causes of the relevant symptoms.

What Are the Treatment Options for Cushing’s Disease in Dogs

“If your vet does decide to prescribe medication, your dog will normally require the medication for the rest of his/her life.”

Treating Cushing's Disease in Dogs

The treatment for Cushing’s disease for dogs depends largely upon the cause: If the cause if due to steroid / corticosteroid prescription drugs, then the treatment could involved simple reducing the dosage of those same medications while being observed by a vet.  It’s important for your vet to decide on the treatment route and not simply stop giving your dog the medications as abruptly ceasing to administer to your dog their medicine may lead to a serious condition an Addisonian crisis.

If Cushing’s syndrome is due to a growth on your pet’s adrenal glands, our vet may decide to perform surgery to remove the growth. However it’s possible that if the tumor has spread throughout the dog’s body, surgery may not be feasible.

If your vet does decide to prescribe medication, your dog will normally require the medication for the rest of his/her life. Drugs are most appropriate for cases in which Cushing’s syndrome is due to the pituitary gland or for those with a tumor on their adrenal gland that can't be removed with surgery.

Your pup will need regular check-ups and blood tests to make sure his treatment is working.

In other cases of Cushing’s disease for dogs, if the symptoms are only mild and are pituitary-dependent, in some cases your vet will adopt a “wait-and observe” approach without any immediate treatment however they should be closely monitored to see if symptoms improve or not. As a general rule of thumb, ideal timing to begin treatment is in correlation with potential symptoms that endanger or are problematic to the dog.

An example of this could be increased blood pressure, potential kidney damage, increased infections and perhaps additional significant quality of life issues (difficulty breathing, frequent urination, etc.).

 If your vet has decided to treat your dog’s Cushing disease (which most likely would be pituitary-dependent), it’s possible that they would prescribe trilostane (Vetoryl). Vetory is a serious medication that can potentially have dangerous side effects so it’s critical for dog owners to take their pets in regularly to the vet for examination and monitoring. Trilostane is also a medication which potentially can interact with other drugs so it’s very important that your vet knows about all other medications you give to your pet.

Vetoryl (trilostane), approved by the FDA in 2008 is the only drug approved to treat both pituitary- and adrenal-dependent Cushing's in dogs. This prescription drug works by stopping the production of cortisol in the adrenal glands. Vetoryl should not be given to a dog that

  • has kidney or liver disease
  • takes certain medications used to treat heart disease
  • is pregnant

Some of the more frequently reported adverse side affects include lack of appetite, vomiting, lack of energy, diarrhea, and weakness. Occasionally, more serious side effects, including bloody diarrhea, collapse, severe sodium/potassium imbalance, and destruction of the adrenal gland may occur, and may result in death. In 2014, with input from CVM, the manufacturer updated the information about patient monitoring and side effects on the package insert. Although not proven to be caused by Vetoryl, some additional side effects reported to CVM and now included on the package insert are adrenal insufficiency, shaking, elevated liver enzymes and elevated kidney tests.

Only one other drug, Anipryl (selegiline), is FDA-approved to treat Cushing's disease in dogs, but only to treat uncomplicated, pituitary-dependent Cushing's.

Veterinarians have often used a human chemotherapy drug, Lysodren (mitotane), "off-label" to treat Cushing's in dogs. Lysodren destroys the layers of the adrenal gland that produce cortisol. It requires careful monitoring and can have severe side effects.

Mitotane (Lysodren) is another option however this is an older drug that is much less prescribed today, partially due to the many side effects it has however it also may cost less than Trilostane.

Another possible scenario could be when your dog is diagnosed with an adrenal tumor, chest radiographs and possibly a CT scan or MRI should be taken to examine the body for any possible metastatic spread of the disease. If no metastases are observed, many time vets will begin treatment with medication (trilostane) for a period of time in order to reduce the tumor’s size and then proceed to do surgery in order to remove it completely.

 How To Manage Cushing’s Disease in Dogs

“You need to be prepared if your dog is being treated with trilostane for Cushing’s disease as this is a serious medication that requires ongoing observation for the rest of your dog’s life.”

Managing Cushing's Disease in Dogs

It’s your responsibility to take your dog in for periodic exams and for observation, depending on the schedule your vet decides. Additionally, you need to be on the lookout for any negative reactions you dog may exhibit including lack of energy, weakness, lack of appetite, vomiting, diarrhea and sometimes difficulty walking. If any of these side effects do occur, you should contact your veterinarian immediately and discontinue medication under their supervision.

Because of the cost and risks associated with use of trilostane, it is often recommended to under-treat rather than over-treat your dog. It is imperative to closely monitor cortisol levels in the blood, as your dog can become very ill if the levels drop too low.

Your veterinarian will schedule regular follow-up visits to monitor for the adverse effects of trilostane and make sure that your dog continues to receive an appropriate dose. While each dog’s individual schedule can vary, but it’s very possible that you may need to take your dog a few times per year for observation.