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Many aspects of your dog’s habits and physique will change as they age. But, if you notice excessive urination, extreme thirst, and visible bodily changes, such as obesity or thin skin, they could have Cushing’s disease (CD).
Key Points
Also known as “hyperadrenocorticism,” this condition is usually caused by a tumor in the pituitary gland. Although it’s found in less than 1% of dogs, because of the complex diagnostic testing required, the number is likely higher. It also requires consistent monitoring and ongoing treatment, which can be expensive.
If your dog has CD, your veterinarian can assess their symptoms to create a well-balanced treatment plan. Without treatment, Cushing’s can seriously hinder a dog’s quality of life and lead to chronic complications. Thankfully, it’s manageable, and most diagnosed dogs can lead happy, fulfilling lives.
What Is Cushing’s Disease in Dogs?
Cortisol is the hormone many associate with the body’s “fight or flight” response. This hormone is produced in the adrenal cortex, which is located on the outer layer of the adrenal glands in front of the kidneys.
The adrenal glands work in tandem with the pituitary gland, which is located at the base of the brain. The pituitary gland releases adrenocorticotropic hormone (ACTH), which tells the adrenal glands to release cortisol. However, a tumor of the pituitary gland or one of the adrenal glands could cause an overproduction of cortisol.
Cushing’s disease is a naturally occurring syndrome, but there is another form that can result from the overuse of corticosteroids: iatrogenic Cushing’s disease. Affected dogs develop symptoms that are identical to naturally occurring CD, and it resolves once the steroids are stopped.
Certain breeds are predisposed to CD, with Poodles, Dachshunds, Boston Terriers, Boxers, and Beagles being especially vulnerable. Cushing’s mostly affects dogs weighing less than 44 pounds, and studies suggest that 75% of dogs affected by CD are female.
Symptoms of Cushing’s Disease
One of the most obvious symptoms of Cushing’s disease is excessive thirst. It may seem as though your dog’s thirst is never sated, or you may find their water bowl constantly drained. Consequently, they may want to go out to urinate at all hours of the day and night. They may even start having accidents in the home. Excessive thirst and urination can also be caused by other conditions, such as kidney disease, diabetes mellitus, and in unspayed female dogs, pyometra.
In addition to excessive thirst and urination, other symptoms of CD include:
- Thinning of the skin
- Lesions
- Hair loss on the dog’s flank, neck, and perineum
- Obesity (most notably around the abdomen, creating a potbelly-like appearance)
- Reduced energy
Since it takes at least a year for these symptoms to develop, and because these symptoms are often mistaken for common signs of aging, many dogs have advanced CD before owners even recognize a problem exists.
Diagnosis of Cushing’s Disease
Diagnosing CD isn’t easy, and it’s not cheap. The diagnostic tests alone can cost hundreds of dollars.
Cushing’s disease can be verified with an ACTH stimulation test. Here, blood is drawn from the patient. Then, they’re given an injection of ACTH, and a second blood test is taken a few hours later. If the dog’s cortisol level goes up a little, their adrenal response is normal. If it starts high and climbs even higher, they have CD.
The veterinarian may also use a second method: the dexamethasone suppression test. In this process, a dog receives an injection of the steroid, dexamethasone. In a healthy dog, the cortisol level decreases over the next few hours because the steroid suppresses adrenal production. If the cortisol level fails to drop, it suggests there is a tumor that’s not responding to the medication.
Ultrasound examinations also allow the veterinarian to determine whether a tumor is present, and if it’s located in the pituitary gland or the adrenal glands.
Diagnostic ultrasounds are often done to help identify abnormalities, such as enlargement or the presence of tumors, in the adrenal glands in dogs with Cushing’s. They can also detect liver metastases. While ultrasound is a crucial tool, veterinarians primarily rely on blood and urine tests to diagnose the disease and determine the underlying cause.
Treatment of Cushing’s Disease
Treatment of the pituitary-induced form of Cushing’s disease is the most complicated. Trilostane (brand name Vetoryl®) is the most commonly used drug. It works by blocking an enzyme involved in hormone synthesis. Mitotane (brand name Lysodren®) is another option. It destroys adrenal tissue and can be associated with more side effects. Selegiline hydrochloride (brand name Anipryl®) and ketoconazole (brand name Nizoral®) are other medications. However, veterinarians consider these to be less effective than trilostane or mitotane, so they’re not typically recommended. On occasion, a veterinarian will offer surgery to remove the pituitary tumor or radiation therapy, which may be an option at certain referral centers.
Treatment of an adrenal tumor requires major abdominal surgery, best performed by a board-certified veterinary surgeon at a tertiary referral. If the surgery is successful, meaning the surgeon removed the entire tumor, and the tumor isn’t malignant, there is a good chance that the dog will fully recover. If surgery isn’t an option, some of these patients can be managed with medication, though they don’t tend to respond as well. Mitotane may be more effective with adrenal tumors as it can be destructive to the cancer itself, though higher doses are required. Radiation may also be an option.
Treating iatrogenic Cushing’s disease requires discontinuing steroid use. The steroid must be discontinued in a controlled, gradual way so that other complications don’t occur. Unfortunately, it usually results in a recurrence of the disease that was being treated with the steroid.
Things to Consider With Medication Management
Your veterinarian will outline a treatment plan tailored to your dog’s condition. Be sure to follow their guidelines closely because these treatments depend on consistent and regular administration of medication. Lifelong treatment may be necessary. Most dogs typically experience few medication side effects during treatment. However, you must carefully monitor them using blood tests and clinical signs. Follow-up blood tests are crucial to ensure your pet is receiving the proper dosage and not too little or too much of the drug, both of which can cause complications.
Talk to your veterinarian for further insight on properly administering these drugs and monitoring for side effects. Careful testing is required to ensure that the drugs don’t destroy all of the cortex and that the cortisol stays at a defined level.
Preventing Iatrogenic Cushing’s Disease in Dogs
There is no way to prevent tumors of the pituitary or adrenal glands from causing Cushing’s in your dog. However, you can prevent the excessive administration of corticosteroids from causing iatrogenic Cushing’s disease, which shares the same symptoms as tumor-related CD. A great preventative measure involves understanding what drugs your dog is prescribed and being mindful of their correct use.
Excessive use of these corticosteroids could cause iatrogenic CD:
- Prednisone
- Prednisolone
- Dexamethasone
- Triamcinolone
- Methylprednisolone
These are potent, synthetic drugs that can last a long time in the body. They’re often prescribed for dogs struggling with conditions that cause pain, inflammation, and itching. Only give these medications as directed by a veterinarian, and be sure to contact them for advice if you notice any changes in your dog’s urination, thirst, or physique.
Managing Cushing’s Disease in Dogs
Managing Cushing’s disease in your pet isn’t overly demanding, but it’s certainly a commitment. It’s a balancing act that involves understanding their hormone levels, tumor’s location, and medication regimen.
To monitor your dog’s condition, their veterinarian will conduct regular tests to assess their cortisol levels, along with other aspects of their health. Expect to be a familiar face at your vet’s office, as some tests must be conducted every 3–6 months.
For some dog owners, the goal of treatment is to mitigate the clinical signs of CD rather than correct the condition itself. There is no better resource than your dog’s healthcare team regarding all aspects of their health, from their diet to their hormone levels and everything beyond. They can offer the information necessary to make informed decisions about what comes next after a Cushing’s disease diagnosis.
This article is intended solely as general guidance, and does not constitute health or other professional advice. Individual situations and applicable laws vary by jurisdiction, and you are encouraged to obtain appropriate advice from qualified professionals in the applicable jurisdictions. We make no representations or warranties concerning any course of action taken by any person following or otherwise using the information offered or provided in this article, including any such information associated with and provided in connection with third-party products, and we will not be liable for any direct, indirect, consequential, special, exemplary or other damages that may result, including but not limited to economic loss, injury, illness or death.