Cushing's Disease Dogs Symptoms

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Cushing's Disease in Dogs

What Is Cushing's Disease in Dogs?

The endocrine system is the collective system of glands that produce and secrete hormones in the body, one of which is the hormone cortisol. At normal levels, cortisol performs many useful functions including helping individuals respond to stress and modulating the immune system, but too much cortisol in the body can do a lot of damage.

The condition associated with an excess of cortisol is medically referred to as hyperadrenocorticism or Cushing’s disease, and it is one of the most common endocrine disorders that affects dogs.

Cushing’s disease can develop when a dog’s own body overproduces cortisol or when a dog is given corticosteroid medications (prednisone, dexamethasone, triamcinolone, etc.) at high doses and/or over a long period of time. Hyperadrenocorticism generally affects middle-aged to older animals.

Cushing's Disease Symptoms in Dogs

Common symptoms associated with Cushing’s disease are listed below. Keep in mind that all symptoms are not apparent in every patient and that many of the signs can also be associated with other diseases. To determine whether or not a dog has Cushing’s disease, a veterinarian will need to look not just at a dog’s symptoms but also at the results of several different diagnostic tests.

• Increased thirst and urination (polydipsia and polyuria, respectively)


• Increased hunger


• Increased panting


• Pot-bellied abdomen


• Obesity


• Fat pads on the neck and shoulders


• Recurrent infections of skin, ears, urinary tract, etc.


• Loss of hair


• Lack of energy


• Inability to sleep (insomnia)


• Muscle weakness


• Infertility


• Darkening of the skin


• Appearance of blackheads on the skin


• Thin skin


• Bruising


• Hard white scaly patches on the skin, elbows, etc. (associated with the disease calcinosis cutis)


• Neurologic abnormalities (circling, behavioral changes, seizures, etc.)

What Causes Cushing's Disease in Dogs?

The most common cause of hyperadrenocorticism in dogs is a benign (non-spreading) pituitary tumor. Malignant tumors of the pituitary, which metastasize through the body, are a much less frequent cause of hyperadrenocorticism. When a dog’s Cushing’s disease develops because of problems within the pituitary gland, the condition is called pituitary-dependent hyperadrenocorticism (PDH). PDH is responsible for approximately 80 to 85 percent of cases of naturally occurring hyperadrenocorticism in dogs. Tumors within the adrenal gland (adrenal-dependent hyperadrenocorticism or ADH) are responsible for the other 15 to 20 percent of cases of naturally occurring Cushing’s disease in dogs. Adrenal tumors have about an equal chance of being benign or malignant.

Excessive administration of corticosteroid medications can also cause hyperadrenocorticism in dogs. These drugs are commonly used to treat allergies, immune disorders and some types of cancer, reduce inflammation, or as replacement therapy for low, naturally-occurring cortisone levels.

Diagnosis

To diagnose Cushing’s disease, your veterinarian will first take a comprehensive health history of your dog and then perform a complete physical exam. Basic lab work like a blood chemistry profile, complete blood cell count, fecal examination, and a urinalysis will likely follow.

If based on this initial assessment your veterinarian suspects that Cushing’s disease is a likely cause of your dog’s symptoms, he or she will then run tests that are necessary to definitively diagnose the condition. The first test is often a urine cortisol:creatinine ratio. If the test results are normal, then your dog probably does not have Cushing’s disease. If your dog has a high urine cortisol:creatinine ratio, then further testing is called for since many conditions can lead to this result.

The most common test used to diagnose Cushing’s disease in dogs is the low-dose dexamethasone suppression test (LDDS). A blood sample is taken to measure a dog’s baseline cortisol level and then a small amount of dexamethasone is administered by injection. Blood cortisol levels are measured four and eight hours after the dexamethasone is given. In a normal dog, the dexamethasone injection inhibits secretion of a hormone that stimulates cortisol secretion, which leads to a decrease in circulating cortisol levels. In a dog with Cushing’s disease, cortisol is not suppressed.

Unfortunately, no one diagnostic test is definitive for Cushing’s disease in all cases. Veterinarians may need to also run an ACTH stimulation test, high-dose dexamethasone suppression test, and/or perform an abdominal ultrasound to determine whether or not a dog has Cushing’s and if so, whether PDH or ADH is to blame.

Treatment for Cushing's Disease in Dogs

Treatment for Cushing’s disease that develops due to corticosteroid medication overuse is fairly straightforward. Dogs should be slowly weaned off of these medications while under a veterinarian’s care. Removing these medications too quickly can lead to a life-threatening condition called an Addisonian crisis.

Dogs with mild symptoms associated with pituitary-dependent Cushing’s disease may not need immediate treatment but should be closely monitored to determine when it would be beneficial. In general, treatment should start when a dog develops symptoms that are potentially dangerous and/or troublesome to the pet or owner. These might include high blood pressure, an increased urine protein:creatinine ratio (evidence of kidney damage), recurrent infections, a noticeable increase in drinking and urinating, urinary accidents, having to get up in the middle of the night to urinate, exercise intolerance, and excessive panting.

Once the decision to treat a dog’s pituitary-dependent Cushing’s disease has been reached, a veterinarian will likely prescribe one of two drugs:  mitotane (Lysodren) or trilostane (Vetoryl). These drugs can have serious side effects, so dogs taking them should be closely monitored. Other medications (ketoconazole, selegiline or cabergoline) may also be used under certain circumstances.

When a patient 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 seen, the dog is often given a medication (trilostane) for a few months to shrink the tumor, followed by surgery to remove it.

Living with and Managing Cushing's Disease

If your dog is being treated with trilostane or mitotane for Cushing’s disease, you need to be prepared to continue treatment for the life of your pet. You will need to be observant for any adverse reactions to these powerful medications. Typical signs of an adverse reaction are lack of energy, weakness, lack of appetite, vomiting, diarrhea, and sometimes difficulty walking. If any of these side effects do occur, you should discontinue the medication and contact your veterinarian immediately. He or she may have given you the medication prednisone to give to your dog under circumstances like these (or during times of stress). Follow your veterinarian’s directions with regard to prednisone use in your dog.

Your veterinarian will schedule regular follow-up visits to monitor for the adverse effects of mitotane or trilostane and make sure that your dog continues to receive an appropriate dose. Schedules vary, but you should be prepared to see your veterinarian several times a year once the maintenance phase of therapy has been reached.

Successful removal of a benign adrenal tumor that was responsible for a dog’s Cushing’s disease should be curative, but if the tumor was malignant the prognosis is more guarded.

Cushing’s Syndrome in Dogs

Cushing's syndrome happens when your dog’s body makes too much of a hormone called cortisol. This chemical helps him respond to stress, control his weight, fight infections, and keep his blood sugar levels in check. But too much or too little of it can cause problems.

Cushing’s, which is also known as hypercortisolism and hyperadrenocorticism, can be tricky for a vet to diagnose, because it has the same symptoms as other conditions. The key is to let your vet know about anything that’s different about your pet.

In some cases, surgery can cure dogs of the problem. If your pup can’t have an operation, he can take medicine to control his cortisol levels.

Symptoms

The condition mostly affects middle-aged and older dogs, and the warning signs may be harder to spot in the beginning.

You might notice your dog:

• Is thirstier than usual


• Seems hungrier


• Pees more often; housebroken dogs may have indoor accidents.


• Loses hair or it seems slow to grow


• Gets a pot belly


• Has thinning skin


• Seems very tired and inactive


• Pants a lot


• Gets skin infections

Types of Cushing's Syndrome

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

There are two major types that affect dogs:

• Pituitary dependent. This form is the most common, affecting about 80% to 90% of the animals who have Cushing's. It happens when there’s a tumor in a pea-sized gland at the base of the brain, called the pituitary.


• Adrenal dependent. This type comes from a tumor in one of the glands that sit on top of the kidneys, called adrenal glands. About 15% to 20% of diagnosed dogs will have this type.

Another kind, called iatrogenic Cushing's syndrome, happens after a dog has taken steroids for a long time.

Getting Your Dog Diagnosed

There’s no method that’s 100% accurate for diagnosing Cushing's. So the vet will do a few tests to see what may be causing your pet's symptoms and to rule out other health problems.

Your vet will start by testing your dog’s blood and his pee. These exams can detect diluted urine, urinary tract infections, or problems with a protein mostly found in the liver and bones called alkaline phosphatase. All of these are common in animals with Cushing’s. If the results show signs of the condition, your vet will follow up with hormone screening tests, such as:

• 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 pup could have Cushing’s, 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.

Treatments

If Cushing’s syndrome comes from a tumor on your pet’s adrenal glands, the vet might be able to remove it with surgery, which will cure him of the problem. But if the tumor has spread to other parts of his body or he has other health problems, surgery may not be an option.

Usually, a dog can live an active, normal life with medication to treat the condition, though he’ll need it for the rest of his life. Drugs are best for dogs with Cushing’s syndrome caused by the pituitary gland or for those with a tumor on their adrenal gland that can't be removed with surgery.

The most common drug is trilostane (Vetoryl). Mitotane (Lysodren) is an older drug that vets don’t prescribe much anymore. It causes many side effects, but it may cost less. Your pup will need regular check-ups and blood tests to make sure his treatment is working.

If your pet has iatrogenic Cushing's syndrome, your vet can try to gradually stop giving him steroids. But the original condition they were treating will probably come back.

The most important thing you can do is to follow your dog's treatment plan. Keep a close watch on his behavior and symptoms, and give him the right medication doses at the right times. You and your vet can work together to help him live a happy, healthy life.