What Is Cushing’s Disease In Dogs?
By Chyrle Bonk, DVM January 07, 2020
Your best friend just received the diagnosis of Cushing’s disease from your veterinarian. At least now you have an explanation for all of their weird symptoms, but where do you go from here? Cushing’s disease in dogs can be a tricky issue to diagnose and control, so let’s look at some of the information surrounding Cushing’s disease so that you’ll have a better idea about what you and your pup is dealing with.
What Is Cushing’s Disease In Dogs?
Cushing’s, or hypercorticolism or hyperadrenocorticism, is a condition in which your dog’s body makes too much cortisol. Cortisol is more commonly known as the stress hormone but is also responsible for weight control, blood sugar regulation, and immune system function, among other things. Cortisol is normally produced in the adrenal glands, near the kidneys. The pituitary gland, at the base of the brain, produces adrenocorticotropic hormone, or ACTH, that signals the adrenal glands to up their cortisol production. Cushing’s disease occurs when there is a malfunction in this feedback pathway, either by the pituitary producing too much ACTH that leads to increased production of cortisol from the adrenals, or by the adrenal glands upping that production on their own. Those malfunctions are usually due to the presence of a tumor on either gland.
The Types Of Cushing’s Disease In Dogs
Since there are multiple glands involved in Cushing’s Disease, there are also multiple types. Each type exhibits the same symptoms but may differ in treatment methods. Those types are:
- Pituitary dependent
This type of Cushing’s is by far the most common, with 80-90% of affected animals falling into this category. Pituitary dependent Cushing’s is just that, a tumor, usually non-cancerous, on the pituitary gland increases the ACTH output to the adrenal glands.
- Adrenal dependent
The other 10-20% of dogs with Cushing’s fall into this category where a tumor on either of the adrenal gland can lead to overproduction of cortisol.
This is the man-made version of Cushing’s where prolonged use of steroids in dogs for other conditions can actually lead to Cushing’s Disease.
How Do Dogs Get Cushing’s Disease?
As you can see from above, dogs most commonly come down with Cushing’s as a result of a tumor. These tumors can be either cancerous or non-cancerous and depending on their size can lead to more issues than just Cushing’s. Some breeds are more prone to Cushing’s than others with poodles, dachsunds, Boston terriers, boxers and beagles being more high risk. This would suggest that there is a genetic component. In the case of iatrogenic Cushing’s, giving your dog high doses of steroids for long periods of time for other conditions, such as skin allergies, can lead to the same symptoms.
Is Cushing’s Disease Contagious?
Dogs are by far the posterchild for Cushing’s disease, but it also occurs in cats, horses, and humans. Since there seems to be a genetic component, Cushing’s may show up among dog relatives, but it is by no means contagious. You may also see Cushing’s in multiple dogs in the same household that are receiving high doses of steroids, but again, it isn’t contagious.
What Are the Symptoms Of Cushing’s Disease In Dogs?
Cushing’s disease is most commonly seen in middle aged dogs, although it can very rarely occur in dogs as young as one year old. All symptoms are due to the overproduction of cortisol, which with its wide range of functions can lead to a wide range of symptoms.
As your journey with canine Cushing’s begins, get ready to hear the terms PU/PD. These stand for polydipsia and polyuria meaning excessive drinking and excessive peeing. It makes sense that excessive thirst, brought on by that increase in cortisol would lead to increased peeing and even indoor accidents as your pup might not have the time to get outside.
- Hair loss
Cushing’s produces a common endocrine-type hair loss that occurs on both sides of the body. The legs and head usually look normal. If your pup is frequently trimmed, you may notice that the hair is slow to grow back, especially in those areas along the sides of the body.
Cortisol also affects the collagen in your dog’s skin, leading to thinning and crepey skin. This can also cause your dog to have a pot-belly as the abdominal skin and muscles aren’t able to keep your dog’s belly taunt and tucked anymore.
- Decrease in activity
Cushing’s disease may leave your dog tired all of the time and uninterested in their normal activities. They may also pant more even if not doing anything.
- Bruising and other infections
Too much cortisol can make your dog’s blood vessels more fragile so that they bruise more easily and to heal more slowly. It can also decrease your dog’s immune responses leading to increased infections of the skin, bladder, or elsewhere.
How Is Cushing’s Diagnosed?
With how varied that list of possible symptoms is, it’s no wonder that Cushing’s isn’t easily diagnosed. To make it worse, there’s no single, right test for Cushing’s. So, diagnosis will heavily depend on the history that you give, the exam, some blood and urine tests, and response to treatment.
If your veterinarian suspects that your dog has Cushing’s, then they will most likely run a blood chemistry and CBC to check organ function and blood cell numbers. If Cushing’s is still on the list, they may test your dog’s urine corticol/creatinine ratio, or bring your dog in for a dexathasone suppression test or ACTH stimulation test. The last two tests typically take all day and require the comparison of multiple blood samples.
If your dog is diagnosed with Cushing’s from any of the above tests, your veterinarian may take abdominal x-rays or ultrasounds to check the adrenals and liver.
What Are The Treatment Options For Cushing’s Disease In Dogs?
The treatment of Cushing’s will largely depend on the type. Let’s start with iatrogenic Cushing’s as it has the least complicated treatment. Since iatrogenic Cushing’s is caused by giving too much steroid, you simply stop giving it. While that may seem intuitive and easy, that’s usually not the case. Steroids need to be stopped in a tapered fashion so that other complications don’t occur. Also, the condition that you were initially treating with the steroids may reoccur, so you’ll have to find a different fix for that.
Other types of Cushing’s can be controlled by surgery or radiation, depending on the location of the problem. Radiation is more commonly used in the case of pituitary-based tumors and surgical removal is more common with adrenal tumors.
For those pups that aren’t good surgical candidates, either due to health or financial reasons, life-long oral medication may be the best answer. The oral medication Mitotane works for both pituitary-dependent and adrenal-dependent Cushing’s by destroying the adrenal cells that produce cortisol. For pituitary-dependent Cushing’s, Vetoryl can also be used to suppress the production of cortisol. Vetoryl tends to have fewer side effects than Mitotane. Both drugs require higher doses for the first 5-7 days of treatment and then a sustaining dose for life after that. Dogs will need to have period checks to ensure the proper dosage and relapse of symptoms is common as dogs get older.
Is Cushing’s Disease In Dogs Curable?
Curing Cushing’s involves the complete removal of the tumor. This is best done while the tumor is small and before it has a chance to spread. However, the surgical removal of a pituitary tumor and even an adrenal tumor may take a highly skilled surgeon and isn’t something that most general practitioners will attempt.
Oral medications don’t cure Cushing’s, they simply maintain it. Oral medications are lifelong and can sometimes take a month or more before you’ll see results. Even with proper dosage and administration, some dogs may relapse after being on the medication and need frequent dosage adjustments.
How Long Can A Dog Live With Cushing’s Disease?
With the proper treatment, Cushing’s can be completely managed in most dogs. Surgical removal of tumors is typically around 90% curative, so a dog will go on to live a normal, healthy life. For dog’s that undergo oral treatment, most signs will begin to resolve within a couple of weeks and others, like hair regrowth, may take several months. Again, oral medications are lifelong and may require adjustments as needed, but most dogs will do well and otherwise live normal lives.
Dogs that have large or spreading tumors have a more guarded prognosis depending on what else that tumor is affecting and if it can be completely removed or not. The cost and convenience of surgery and the medications will also affect the prognosis as some dog parents may not be able to take on an aggressive enough treatment. I have had several clients start the medication only to stop it, not under my advisement, once the symptoms cleared up. They would then restart the medication once their dog started showing signs again. This isn’t how the medications were intended and these dogs, as you can imagine, experience a rollercoaster ride of feeling great to feeling horrible as long as their owners keep trying this approach.
What Can I Do To Help My Dog With Cushing’s Disease?
The best thing you can do for your pup with Cushing’s is to follow your veterinarian’s advice. Be aware that treatment options are not cheap and they may require some discipline, but as you can probably see from above, it’s not in your dog’s best interest to disobey veterinary orders. Since Cushing’s is tough to diagnose, second opinions should be welcomed.
Other things you can do to help your pup would be symptomatic relief. They’re going to have excessive hunger and excessive thirst, so be sure to offer them plenty of fresh water and consider feeding smaller meals more frequently or provide low calorie snacks, like carrots or green beans, to help curb their hunger. Make sure they can quickly and easily get outside to avoid those indoor potty accidents. Have your dog groomed to help with the hair loss and to prevent mats or skin infections, and some dogs may appreciate a supportive belly band to help keep their tummy tucked.
Having your dog diagnosed with Cushing’s disease doesn’t mean it’s the end. Proper diagnosis by your veterinarian and proper treatment followed out by you could mean your dog will continue to lead a normal, happy life. With all of the variations that Cushing’s disease may take, it’s important to take note of any off behaviors and speak to your veterinarian about anything concerning.