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Cushing's Disease in Dogs: Understanding, Diagnosing, and Treating

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Cushing's Disease in Dogs: Understanding, Diagnosing, and Treating

Tired Dog Laying on the Floor

Has your dog been drinking their water more quickly than usual even with extra refills? Or maybe your housetrained pooch had an accident or been requesting extra night time potty breaks?  Perhaps you’ve also noticed your pup devouring every meal with even more than their typical enthusiasm. All of these indicators may be clinical signs pointing to the possibility of Cushing's syndrome in your dog.

Cushing's Disease, scientifically called hyperadrenocorticism, usually happens in middle aged or senior dogs when their bodies create too much of the stress hormone cortisol. Cortisol is a very useful and necessary hormone that helps with stress response, metabolism, and many other important bodily functions. However, excess cortisol impairs the immune system and often leads to infection, inflammation, and other health maladies like cushing’s disease.

Types of Canine Cushing Disease

Most cases of dog cushing's disease happen because of tumor development in either the pituitary or adrenal gland. A gland tumor in either one of these locations stimulates the adrenal glands, and generates excess cortisol production

Pituitary Dependent Cushing's Disease

Pituitary dependent cushing syndrome is the most common type of Cushing's disease and is responsible for roughly 85% of cases. Also known as pituitary gland adenoma, it is caused by a tumor in the small gland at the base of the brain. A pituitary tumor is usually small and benign, but can trigger excess production of the hormone ACTH, also called adrenocorticotropic hormone. 

Adrenal Dependent Cushing's Disease

Instead of being caused by pituitary tumors, adrenal dependent cushing is the result of adrenal tumors. An adrenal gland tumor would be located in one of the adrenal glands above each kidney and may affect production of an array of hormones regulating an array of essential functions. Around 15% of cushing disease occurrences in dogs are this adrenal variety.

Iatrogenic Cushing's Disease

The final type of cushing disease is called iatrogenic cushing syndrome occurs as the direct result of a dog taking steroids for an extended time period. Although originally prescribed by a veterinarian for legitimate medical treatment, prolonged use of these steroids also elevates cortisol levels above the healthy range, leading to cushing's disease. Because this type of Cushin’s syndrome is resolved with cessation of steroid medication, we will not be further exploring it's diagnosis or treatment.

Breeds with Higher Cushing's Risk

While a direct link has not been scientifically proven, the risk of cushing s disease may be influenced by genetic factors and breed differences. Breeds prone to developing cushing s disease include:

  • Boxers
  • Dachshunds
  • German Shepherds
  • Poodles
  • Yorkshire Terriers
  • Labrador Retrievers
  • Maltese
  • Cocker spaniels
  • Australian shepherds

Dog eating quickly from food bowl

Signs of Cushing's Syndrome in Dogs

Because the production of cortisol impacts a wealth of biological processes, the familiar signs and symptoms of cushing's disease are also many in number and often come on slowly, cushion’s is frequently misattributed to other health conditions. 

Common symptoms of cushing's disease in a dog include:

  • Drinking more water and faster than usual
  • Urinating - dogs may have accidents inside despite being housebroken
  • Thin skin/skin infections
  • Hair loss
  • Fatigue
  • Increased appetite
  • Pot belly
  • Heavy panting
  • High blood pressure
  • Impaired immune system and increased risk of infection 

If your pup shows any of these symptoms or warning signs of potential cushing's disease, contact your veterinarian promptly, so they can determine whether medical treatment is necessary.

Diagnosing Cushing's Disease in Dogs

Before starting a veterinary treatment plan for cushing's, an accurate diagnosis must be made for your dog. Although there is not a single method for diagnosing cushing in dogs, a veterinarian will usually start with blood and urine tests. The amount of cortisol regularly fluctuates, so diagnosing Cushing's syndrome is not as straightforward as simply measuring the quantity of cortisol present in your dog's blood. 

Types of Diagnostic Testing for Dog Cushing's Syndrome

Cortisol levels regularly fluctuate, so diagnosing Cushing's syndrome is not as straightforward as simply measuring the levels of cortisol in your dog's blood. An integrated approach may be necessary, and your vet will likely combine several examination methods along with the symptoms you’ve reported in order to reach their final diagnosis.

Urine tests
Your veterinarian may start their diagnostic workup for cushing s syndrom with a urine sample from your dog to evaluate their urine cortisol as well as check for presence of urinary tract infection -- UTIs as well as diluted urine are common in dogs with cushings. A urinalysis can also alert your vet to abnormal amounts of protein in your dog’s pee, which are quantified using a creatinine ratio.
Blood Tests
There are two main types of blood tests vets use to detect cushing's syndrome in dogs:
  1. ACTH Stimulation Test - measures cortisol before and after injection with adrenocorticotropic hormone to determine that adrenal gland and pituitary gland functions produce the hormone normally. In healthy animals, there will be an increase.
  2. Low Dose Dexamethasone Suppression Test - measures levels of the stress hormone before and after injection with dexamethasone to determine whether pituitary and adrenal gland response is normal. This test is like the reverse of the ACTH stimulation test because a decrease occurs in healthy dogs.
Ultrasound/MRI Detection of Canine Cushing’s
Dogs cushing's disease may also be confirmed by performing an ultrasound of the abdomen. An enlarged adrenal gland, liver irregularities, or a visible tumor are all signs of possible cushings. Ultrasounds cannot be used to rule out an adrenal tumor as they may be too small for detection. Magnetic resonance imaging (MRI) may be used to discover pituitary tumors.

Treatment Plan for Pituitary and Adrenal Tumors

Advances in internal medicine have greatly increased the array of veterinary treatment options and methods used to treat dogs with this disease. Your dog’s care may include surgery, medication, radiation, or a combination of these methods. 

Surgical removal is the only method known to “cure” hyperadrenocorticism in dogs, but this procedure is often very complicated, resulting in additional risks to the animal. For adrenal dependent cases, a complete excision of the affected adrenal gland including the adrenal tumor is performed. For pituitary dependent cushings, a surgery called hypophysectomy to remove the pituitary tumor is gaining popularity as a viable treatment although it may cost up to $10,000.

Most veterinarians still prefer addressing and managing both types of Cushing's in dogs with medication. The two most common medicines for cushing treatment include:

  • Trilostane was the first prescription approved by the FDA to treat cushings disease in dogs and works in the adrenal glands to halt production of stress hormones. Vetoryl has been approved to treat both adrenal dependent and pituitary dependent forms of this disease, but may not be an option for dogs with kidney/liver issues or an active pregnancy.
  • Mitotane is an anti-cancer medication that vets often prescribe "off label" in caring for cushing’s syndrome dogs.

Continued veterinary check-ups and vigilant monitoring through blood tests and adjusting medication is crucial to increase an animal’s prognosis. Dosage will likely need to be adjusted over time as the tumor develops as well as to mitigate any side effects.  

Prognosis for Dogs Hyperadrenocorticism 

Prognosis for dogs with cushings depends on several elements including the size and location of the tumor and whether it is benign or malignant. 50% of adrenal gland tumors are benign -- when these are surgically removed, it can effectively cure the disorder. Medication therapy may keep the severe side effects of cushing’s at bay, extending the life of your dog by many years. Once diagnosed with pituitary cushing’s, dogs taking medicine live on average for two to three additional years depending on the size of their tumor. Prognosis is the worst for dog’s with malignant adrenal tumors, but medication with trilostane can extend life expectancy by roughly a year.

Quality of Life for Dogs with Cushing

Happy Dog Smiling at Beach with Owner

Once diagnosed and under veterinary care, many dogs with Cushing 's disease go on to live happily and comfortably for years. Sometimes medications may result in unpleasant side effects for your dog, but your pet’s overall health will be much better than a dog with an undetected gland tumor.