You’ve always loved the sheen in your dog’s furry coat. Lately, however, your furry friend is losing hair and doesn’t look so furry anymore. Your dog is also drinking and eating excessively and doesn’t seem his usual energetic self. Ruling out Cushing’s disease in your dog early can save his life.
You might have heard that these are among the clinical signs of Hyperadrenocorticism, a disease commonly known as Cushing’s disease. Could your dog be suffering from the severe and potentially fatal disease?
This article addresses the apprehension dog owners develop around a possible Cushing’s disease diagnosis in their dogs. It will answer all your questions around signs, diagnosis, treatment, and prognosis of Cushing’s disease in dogs. We will be starting with the most basic one: What is Cushing’s disease in dogs?
What is Cushing’s Disease in Dogs?
Cushing’s disease is a severe health condition in dogs triggered by the overproduction of the hormone known as cortisone (cortisol).
According to the Veterinary Teaching Hospital of Washington State University, Cushing’s disease is diagnosed in around 100,000 dogs every year in the United States. These dogs are mostly above 6 years of age, but younger dogs can also suffer from Cushing’s disease.
The hormone cortisone is produced by the adrenal glands, two pea-sized glands located next to the kidneys. However, the adrenocorticotrophic hormone (ACTH) produced by another small gland known as the pituitary gland at the base of the brain directs the adrenal glands to produce cortisone.
A benign or cancerous tumor in the pituitary gland is the leading cause of cortisol overproduction. The tumor distorts the messages sent by the pituitary gland to the adrenal gland, explaining the overproduction of cortisone and the resulting hyperadrenocorticism.
In some cases, Cushing’s disease may also be caused by a tumor on the adrenal glands or by consistent use of steroids on your dog. We’ll tell you more about these different causes of Cushing’s disease in a bit, as they also define the types of the disease.
Overall, though, overproduction of cortisol triggers serious health issues in dogs, including kidney dysfunction and diabetes. Besides, Cushing’s disease is potentially fatal.
Note that there are other alternative names for Cushing’s disease:
- Hyperadrenocorticism (the medical term for the disease).
- Cushing’s Syndrome.
Types and Causes of Cushing’s disease in Dogs
We address the types and causes of Cushing’s disease under the same section because the causes differentiate the types.
There are 3 different types of Cushing’s disease in dogs:
- Pituitary-dependent Cushing’s disease.
- Adrenal-dependent Cushing’s disease.
- Iatrogenic Cushing’s disease
Pituitary-dependent Cushing’s Disease
Pituitary-dependent Cushing’s disease is the most common of the three types of hyperadrenocorticism, accounting for 80% to 85% of the cases. It is caused by a benign or malignant tumor of the pituitary gland.
A tumor on the pituitary causes overproduction of the adrenocorticotrophic hormone, which overstimulates the pituitary gland to produce more cortisone than the dog’s body needs.
Because pituitary gland tumors can be large, they can also trigger signs that are not typical of Cushing’s disease, including neurological signs. Besides, enlarged tumors create pressure on the tissues adjacent to the pituitary.
While most dogs with pituitary-dependent Cushing’s disease can live normal lives with proper mediation and disease management, 15% of these cases manifest neurological signs and have an unfavorable prognosis.
Adrenal-dependent Cushing’s Disease.
Adrenal-dependent Cushing’s disease is caused by a benign or cancerous tumor in one or both adrenal glands.
Surgical intervention can successfully remove benign tumors of the adrenal glands, often with complete cure, but it is often discouraged for the risks involved. Malignant adrenal gland tumors mostly come with an unfavorable prognosis, even when the risk of surgical removal of the tumor is taken.
Iatrogenic Cushing’s Disease
Iatrogenic Cushing’s disease is caused by the consistent use of oral or injectable steroids on your dog. Even though the steroids are used for a curative function, their continued use comes with adverse effects on your dog’s health.
What are the Symptoms
Irrespective of the type of Cushing’s disease that a dog is suffering from, the clinical signs are essentially the same. Dogs with Cushing’s disease will manifest the following clinical signs:
- Excessive thirst and drinking.
- Increased urination.
- Increased appetite.
- Hair loss.
- Drowsiness and reduced activity.
- Muscle weakness.
- Fragile and thinning skin.
- A bloated or potbellied appearance due to increased fat in the abdominal organs and weakened abdominal muscles.
- Excessive panting.
- Recurrent skin infections.
- Dark spots (hyperpigmentation).
- Poor skin healing.
- Recurrent bladder infections, and in some cases, urinary incontinence.
- Sudden blindness in some cases, especially those with pituitary-dependent Cushing’s disease.
Once you notice any of these signs, your next question will be, what should I do if my dog shows signs of Cushing’s disease? The best move is to immediately consult with your dog’s veterinarian and have your dog tested for Cushing’s disease. We’ll address Cushing’s disease diagnosis in a bit, but we thought you’d be curious about what the disease does to your dog.
What Does Cushing’s Disease Do to Your Dog?
If left untreated or is poorly managed, Cushing’s disease can compromise your dog’s overall quality of life. In addition, untreated Cushing’s disease can be the basis for other medical issues in your dog, including:
- Kidney disease resulting from protein loss through frequent urination.
- Bladder stones.
- High blood pressure.
- Chronic skin infections.
- Chronic urinary tract infections (UTIs)
- Vacuolar hepatopathy (a disease of the liver).
- High blood pressure
- Neurologic signs, especially in dogs with pituitary-dependent Cushing’s disease.
- Increased risk for fatal blood clots (pulmonary thromboembolism).
How is Cushing’s Disease Diagnosed?
Upon suspicion of Cushing’s disease, your dog’s veterinarian will conduct a physical examination and some tests to check your dog for Cushing’s disease and rule out other possibilities.
Several tests can be done to diagnose a dog for Cushing’s disease. Often, multiple tests are done to ensure an error-free diagnosis.
An ACTH stimulation test – to determine how well the adrenal glands respond to adrenocorticotropic hormone in the production of cortisol.
A low-dose dexamethasone suppression test (LDDS) – to determine if the secretion of the adrenocorticotrophic hormone by the pituitary gland can be suppressed.
An Endogenous ACTH levels test – to check the level of ACTH in the dog’s body and is usually done after an already positive Cushing’s disease test. ACHT is higher if the dog has a case of Pituitary-dependent Cushing’s disease and lower when it’s a case of Adrenal-dependent or Iatrogenic Cushing’s disease.
A high-dose dexamethasone suppression test (HDDS) – The test is done when a positive Cushing’s disease test has already been made. The test has the same purpose as the low-dose dexamethasone suppression test. The intent is to create a partial or complete suppression of ACTH overproduction in dogs with Cushing’s disease using up to 8mg of Dexamethasone.
Urine cortisol to creatinine ratio test – dogs with Cushing’s disease have high cortisol: creatinine ratio.
Abdominal ultrasound – to detect the presence of tumors on the adrenal glands and tell their size. The test also helps rule out other diseases that bear symptoms similar to Cushing’s disease, such as bladder stones, liver or spleen tumors, gallbladder disease, chronic inflammatory liver disease, or gastrointestinal disease.
Magnetic resonance imaging (MRI) – gives a more conclusive diagnosis for the presence of tumors on the adrenal glands and is considered the most effective. However, it can be a strain on the dog owner’s pocket.
Magnetic resonance imaging or computerized tomography scan – to spot any pituitary tumors.
With these tests, confirmation of Cushing’s disease requires that treatment be started immediately.
What are the Treatments
There are drug and surgical treatment options for Cushing’s disease. However, it is very important to know which ones are approved and the disease management and curative chances for each. Some treatments will work for one type of Cushing’s disease and not for others. The treatment options are explained below.
FDA-Approved Treatment Options
There are two FDA-approved drugs for the treatment of Cushing’s disease:
- Vetoryl (Trilostane)
- Anipryl (Selegiliine)
Vetoryl is used for the treatment of both pituitary-dependent and adrenal-dependent Cushing’s disease. The drug works by stopping the production of cortisone in the adrenal glands.
However, Vetoryl can have severe side effects on dogs and should not be used with pregnant dogs, dogs with liver or kidney disease, and those using medication for heart disease.
Side effects from Vetoryl usage include:
- Poor appetite.
- Diarrhea (can be bloody in serious cases).
- Low energy.
- Severe potassium or sodium imbalance.
- Damage to the adrenal glands.
- Adrenal insufficiency.
- Elevated kidney tests and liver enzymes upon testing.
Anipryl is used to treat mild Pituitary-dependent Cushing’s disease.
Off-Label Cushing’s Disease Treatment Options
Although used off-label, Lysodren (Mitotane) is often used by veterinarians to treat Cushing’s disease in dogs.
Lysodren is a chemotherapy drug for human treatment. However, it can legally be prescribed for animal treatment and for diseases not included in the label, which is why it is described as ‘used off-label.’
The drug destroys the cortisone-producing layers of the adrenal glands but is known to have adverse side effects.
Surgical Treatment for Cushing’s Disease
Though not highly advised, surgical intervention is a possible option for treating Adrenal-dependent Cushing’s disease. As a matter of fact, it is the only conclusive way for curing this type of Cushing’s disease if the tumor is benign and is removed entirely.
However, a surgical intervention to remove a tumor of the adrenal glands is complex and comes with high risks. If successful, your dog has a favorable prognosis and resumes a normal life.
Treatment for Iatrogenic Cushing’s disease
Because it is a drug-induced hyperadrenocorticism, Iatrogenic Cushing’s disease is treated by gradually reducing the steroid dose until it can be stopped completely.
Treatment for Iatrogenic Cushing’s disease is complex because, on the one hand, it means the disease being treated with steroids will take its course without treatment. On the other hand, however, not stopping the steroid treatment means Cushing’s disease will progress.
With Cushing’s medication, your dog will need regular vet visits for ACTH stimulation tests to check how effectively the adrenal glands are responding to the adrenocorticotropic hormone. These regular visits should be continued until cortisol overproduction can be controlled.
For all three types of Cushing’s disease, your dog will need consistent close monitoring by both you and the vet for any signs of disease progression or adverse treatment side effects. In addition, your dog’s vet will occasionally adjust the treatment, depending on how your dog is responding and the advancement of the disease.
But what happens after treatment is given? Let’s discuss a few details on Cushing’s prognosis.
Prognosis and Life Expectancy
The prognosis for dogs with Cushing’s syndrome will vary depending on the type and severity of the disease. In addition, most Cushing’s disease patients are senior dogs, which also impacts treatment.
- Generally, dogs with Pituitary-dependent Cushing’s disease live for an average of 2.5 years with proper treatment. Dogs with smaller and benign pituitary tumors and for whom medication, if followed faithfully, can live a normal and longer life. Those with larger and malignant tumors usually have an unfavorable prognosis.
- With Adrenal-dependent Cushing disease, the prognosis is favorable for 50% of dogs with benign adrenal tumors and who have successful surgical interventions. The prognosis is generally poor for the remaining half with malignant tumors, and the life expectancy is given at approximately one year, and less if the cancer has already metastasized.
In younger dogs, proper treatment for Cushing’s disease comes with a favorable prognosis, with signs of the disease disappearing gradually until they can live a normal life. The excessive appetite and water consumptions signs disappear a few weeks into treatment. However, lost fur may take months to grow back.
Dog owners usually want to know everything about the potentially fatal Cushing’s disease. Here are a few questions of interest about the disease among dog owners.
The saying that a healthy dog is a happy dog is every dog owner’s desire. However, the happy dog dream can slide through the window when severe and potentially fatal diseases like Cushing’s disease strike.
While you may not prevent the growth of pituitary and adrenal tumors in your dog, you can provide your dog with a happy and healthy life by giving the best care, which is a preventive basis for any disease.
Take notice of any clinical signs of Cushing’s disease, such as excessive appetite and drinking, frequent urination, and fur loss. When noticed, report these signs immediately to your dog’s vet. Earlier diagnosis and treatment give your furry friend a better chance for survival and normal life.