In the United States, approximately 100,000 dogs are diagnosed with Cushing’s disease every year. While the condition can also occur in cats, it is rare.
It is a disease where early diagnosis is often missed because some symptoms are dismissed as simply being age-related. So, it's important for all pet owners to understand what Cushing’s disease is and how to recognize its clear clinical signs so treatment can begin.
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What Is Cushing’s Disease?
The medical term for Cushing’s disease (also known as Cushing’s syndrome) is hyperadrenocorticism (HAC).
When HAC is translated, it literally describes the disease.
Let’s break it down:
- “Hyper” means overactive.
- “Adreno” means adrenal gland.
- “Corticism” makes reference to the outer part of the adrenal gland known as the cortex.
Located near the kidneys, the adrenal glands produce hormones that regulate different body functions and are essential to sustain life. One of those well-known hormones is cortisol.
Cushing’s disease occurs when there is excessive and persistent cortisol, produced by the cortex of the adrenal gland, in the bloodstream.
The excessive production of cortisol that results in Cushing’s disease can be caused in one of three ways. There is a different treatment and outcome for each. Therefore, identifying the cause is essential.
Causes of Cushing's Disease
Iatrogenic Hyperadrenocorticism
This form of Cushing’s disease is caused by long-term and high-dose use of cortisol-like drugs such as prednisone, Depo-medrol, dexamethasone, or progesterone-type drugs.
Extended use of these medications can cause the body to suppress normal cortisol production. This results in an overstimulation of the adrenal glands, causing them to produce too much cortisol.
To avoid this form of Cushing’s, your veterinarian will carefully manage the dosage of these medications and the time they receive them.
Additionally, whenever possible, seeking alternative forms of management is helpful. For example, since steroids are often used for allergies and inflammation, seek out treatment alternatives such as biological therapy (immunotherapy), holistic therapy, diet change, and supplements.
See how this type and the other types of Cushing's are treated below.
Pituitary-dependent Cushing’s
This form of Cushing's occurs in about 80% to 85% of canine cases and 80% of feline cases.
Tumors of the pituitary gland, which are located at the base of the brain, can be benign (harmless) or malignant (cancerous).
The tumor causes the pituitary gland to overproduce ACTH, a hormone, which causes the enlargement of both the adrenal glands, causing them to overproduce cortisol.
The size of the tumor can vary from microscopic to large. A large tumor can cause symptoms in pets that are different from those commonly associated with Cushing’s disease because the larger size of the tumor can affect nearby areas.
Symptoms, which may not be associated with Cushing's initially, that can indicate a large pituitary tumor include:
- Decreased alertness
- Listless (less energy and excitement than their normal self)
- Poor appetite progressing to loss of appetite (anorexia)
- Restlessness
- Loss of interest in normal activities
- Episodes of disorientation or confusion
- Later signs noted when the tumor has been present for some time can include behavioral and neurologic changes, abnormal gait, and aimless pacing
Adrenal-dependent Cushing’s
A benign or malignant tumor in one or both of the adrenal glands accounts for the other 15% to 20% of canine and 20% of feline cases of Cushing’s disease.
Predisposing Risk Factors for Cushing's Disease
Age
Cushing’s disease typically occurs in middle-aged to older pets. For dogs, that is between 7 and 12 years of age, with the average age being about 10 years old. However, it can be found in younger and older dogs.
For cats, that is between 7 and 14 years of age, with the average age of diagnosis being 10 years. But the disease has been diagnosed in cats as young as 4-years-old.
Gender
Cushing's disease in cats mainly affects females, who make up 3 out of 4 cases. There is no sex predilection for Cushing’s disease in dogs; both males and females get the disease equally.
Breed
While there is no known cat breed predisposed to Cushing’s, there are certain dog breeds that are predisposed or have a higher risk for developing it. These include:
- Bishon Frise
- Boston Terrier
- Border Terrier
- Dachshund
- German Shepherd
- Jack Russell Terrier
- Lhasa Apso
- Miniature Poodle
- Miniature Schnauzer
- Staffordshire Terrier (American/Bull)
- Yorkshire Terrier
Life Expectancy for Pets with Cushing's Disease
The life expectancy for a dog with Cushing’s is based on the cause of the disease.
Pituitary–dependent Cushing’s:- Average survival for medical therapy is 2 to 2.5 years
- Average survival for surgical removal or radiation is 2 to 5 years
- Average survival time for medical therapy is 1 year
- Average survival for surgical removal is 1.5 to 4 years
The life expectancy for a cat with Cushing’s disease can range from months to years, depending on early diagnosis and appropriate treatment.
The Clinical Signs of Cushing’s Disease
The symptoms you may notice in your pet are the result of the different effects cortisol has on their body. Clinical signs can vary and tend to come on gradually. Due to the slow onset of this disease, many pet owners dismiss the symptoms as normal age-related changes.
Common symptoms of Cushing's to look for include:
- Increased thirst and urination
- Incontinence (urinary)
- Increased appetite
- Pot-bellied appearance
- Muscle loss and weakness
- Weight gain (early stages for cats)
- Lethargy
- Exercise intolerance (decreased ability to maintain physical activity)
- Hair thinning and loss
- Poor coat condition
- Thin skin
- Blackheads and darkening of the skin
- Poor wound healing
- Persistent or recurring skin infections
Another symptom, seen more commonly in dogs but cats can develop it too, is calcinosis cutis. Calcinosis cutis is a condition of the skin where calcium deposits under the skin, causing raised, hard, small nodules.
Symptoms specific to cats
While cats and dogs exhibit similar symptoms for Cushing’s disease, there are two symptoms noted in cats that are not seen in dogs.
One is the development of thinning and weakening skin to the point that it can spontaneously tear. The second is their unusual curling inward of their ear tips. You can see an image of a cat's curled ears in this American College of Veterinary Pharmacists newsletter.
Diabetes and Cushing's
About 80% of cats and only 10% of dogs develop diabetes mellitus. This is important because while Cushing’s causes dogs to drink excessively, it is the diabetes, which is usually diagnosed first, that causes cats to drink excessively.
The non-diabetic Cushing’s cats do not drink excessively.
How Cushing’s Disease Is Diagnosed
There isn’t one ‘best’ test for Cushing’s, such as with diabetes or kidney disease. Diagnostic tests can have false positives and negatives. Therefore, a series of different tests is often required for diagnosis.
A correct diagnosis requires a thorough approach. The process to diagnose Cushing’s begins with a comprehensive evaluation by your veterinarian. They will need you to provide as much detail about your pet’s medical history as possible, as well as any changes you have noticed.
During the physical examination portion, your veterinarian will be evaluating your pet’s overall health, body condition (weight, muscle mass), and will try to determine if there are any visible signs of Cushing’s.
Based on your pet’s symptoms and examination findings, your veterinarian will recommend some initial lab work, which will generally include one or more of the following:
- Complete blood count (CBC)
- Biochemistry panel (evaluates blood sugar levels, liver and kidney values, cholesterol, etc.)
- Urinalysis
- Urine cortisol: creatine ratio (UCCR) – this test can be added to the urinalysis test
- Thyroid test
- X-rays of the abdomen and chest
- Skin biopsy
Following these initial tests, if your veterinarian suspects that Cushing’s disease is the cause of your pet’s clinical signs, your veterinarian will recommend specialized tests to confirm Cushing’s disease and determine the type. Such tests include:
- ACTH stimulation test
- Low-dose dexamethasone suppression tests (LDDST)
- High-dose dexamethasone suppression test (HDDST)
- Endogenous ACTH level test
- Abdominal ultrasound
While there is a lot of testing, which can be expensive (between $500 and $1500), it is essential so that your veterinarian can determine the best treatment protocol for your pet as well as provide you with a prognosis.
How Cushing’s Disease Is Treated
Treatment for Cushing’s is dependent on the type.
Cushing’s disease is a chronic disease, and most pets often have other concurrent medical conditions. Treatment can be drawn out, generally lifelong, and expensive. Treatment can potentially cause some serious side effects that are more serious than the clinical signs of Cushing’s.
Treatment options include:
Medications for all types of Cushing's: For dogs, there are few medications available to suppress cortisol production. Unfortunately for cats, the options are more limited. The purpose of medically treating Cushing’s is to control the disease and provide a better quality of life. Most medications take some time before there are improvements in your pet’s condition.
Discontinuation of steroidal medication: Treatment for iatrogenic Cushing’s requires a controlled and gradual discontinuation of the medication causing excessive cortisol production. The downside is that the disease that was being treated by the medication usually reoccurs. Additionally, in some cases, the medication has done adverse damage to the adrenal glands that often requires treatment.
Surgery – adrenalectomy: This is the removal of the adrenal gland, which can be a good treatment option when only one adrenal gland is affected or the tumor is benign.
This option can cure the disease for benign adrenal tumors. In either case, pets often require initial support medications following the procedure.
Surgery – hypophysectomy: This surgery should be performed by a board-certified veterinary surgeon and may be an option for some pituitary gland tumors. However, this procedure is generally only done in extreme cases since it is very challenging and potentially risky.
Radiation therapy: This procedure is used for large pituitary tumors, especially those causing neurological signs. Radiation therapy can potentially shrink the tumor and decrease cortisol production. This treatment may be combined with medication or surgery.Caring For Your Cushing’s Pet
Manage Stress
An important aspect of caring for your pet when they have Cushing’s is to be sure to decrease stress as much as possible. Stress causes pets to release cortisol, and Cushing’s pets already have more than they need.
Be sure to create an environment that is quiet, calm, consistent, and free of stress triggers. If your pet tends to be anxious or stressed, or triggers are unavoidable, find ways to help calm them. For cats, consider reading our helpful article, “Do You Have a Stressed-Out Kitty?”
To help a dog deal with stress, here are some resources:
Dietary Adjustments
It is important that your pet be maintained at their ideal body weight since excess weight adds more stress to their already weakened muscles and joints.
Maintaining your pet on a diet that optimizes their well-being is essential. It is important that their diet provides them with adequate nutrition to maintain muscle mass, aids in gut health, and reduces inflammation.
There are supplements that can be added to your pet’s dietary regimen that can be highly beneficial. For example, omega-3 fatty acids (fish oil) help decrease inflammation, probiotics help maintain gut health and improve the immune system, milk thistle and S-Adenosylmethionine (SAMe) protect and support the liver, and joint supplements help improve pets’ mobility.
Please consult with your veterinarian and/or a holistic vet when choosing supplements for your pet.
Mobility Support
Unfortunately, pets with Cushing’s have stiff joints and weak muscles.
An important part of keeping your pet mobile is to be sure they have daily but gentle exercise. Can’t get your Cushing’s dog outdoors, no problem, read “How to Exercise Your Dog Indoors”. To help your cat with exercise, use these senior exercise tips.
There are lots of simple, inexpensive, and effective things you can get and do to improve your pet’s mobility. Read these articles, “How to Help an Older Dog with Arthritis and Other Mobility Problems” and “How to Help Cats with Arthritis and Other Mobility Issues,” for helpful tips.
As mentioned above in dietary adjustments, joint supplements can be beneficial. They help support joint health, ease pain, and decrease inflammation. Check out these dog joint supplement recommendations and these cat joint supplements.
Early diagnosis of this disease is essential for your pet to have the best quality of life. That is why it is critical that pets are routinely examined by their veterinarian as well as have routine lab work. Work with your veterinarian to keep your pet on the path of good health!
