Cushing Syndrome in Dogs
What Is Cushing Syndrome?
Cushing syndrome or disease is a condition affecting humans and pets wherein there is an overproduction of steroid hormones. This can either be a result of the pituitary gland doing the increased production or the adrenal gland causing the overstimulation and production of the hormone. In the latter case, often times there is a tumor associated with the condition. In layman's terms, Cushing's is too much cortisol being manufactured in the body. Cortisol affects our ability to respond to stress, helps us fight infections, and keeps blood sugar in check. It does the same in our dogs.
Roughly 80% of Cushing's in dogs results from the pituitary variety and nonsurgical means are used to treat the disease. Since oral treatments can be used to treat the disease, usually more invasive testing is not performed in order to distinguish whether or not the disease is being caused by the adrenal gland versus the pituitary gland.
However, if it is clear that an adrenal tumor is responsible for the symptoms, then surgery may be a viable option. Radiation may also be considered if there is a tumor and it is found. Radiotherapy is used to shrink the size of tumors though, not cure them or destroy them.
Prevalence of Cushing Syndrome in Dogs
- There does not appear to be any correlation of Cushing syndrome amongst certain breeds of dogs.
- The mean age of detection is 6-7 years of age.
- It can be detected as young as 2 years of age and as old as 16 years of age, however.
- Male versus female shows no correlation either. There is no predominance in gender to contracting the disease.
- About 80% of cases are due to a pituitary tumor or overproduction of the pituitary variety of the hormone ACTH.
- About 20% are due to the adrenal gland variety.
Symptoms of Cushing's in Dogs
- Increased water consumption (polydipsia)
- Frequency of urination (polyuria)
- About 80% of animals with the disease have increased appetite (polyphagia)
- Enlargement of the abdomen in 80% of dogs (potbelly appearance)
- Hair loss - between 50% and 90% of dogs usually have this symptom
- Thin skin or slow-to-heal skin - one of the most common presenting symptoms
- Excessive panting
- Fatigue or listlessness
- Recurrent urinary infections
- Loss of reproductive ability
- Acne or pustules
Diagnosing Cushing Syndrome
Just like humans who are suspected of having Cushing syndrome, blood tests are the first line of diagnosis. Usually tests include a complete blood count (CBC), a urinalysis, and a metabolic or blood chemistry panel.
It should be noted that there is not just one test that is specifically used to diagnose Cushing disease. The diagnosis is usually made on the basis of several tests and the overall health history and symptomatology the dog is exhibiting.
The three most common screening tests that are used next would include a urine cortisol to creatinine ratio, a low-dose dexamethasone suppression test and an ultrasound.
The cortisol/creatinine ratio is usually sent out to special labs and although if abnormal can be diagnostic, other causes can give a result that is not normal.
The dexamethasone suppression test in 90% of dogs with Cushing's will show no decrease in cortisol levels 8 hours after administration while normal dogs will show a marked decrease in cortisol levels.
An abdominal ultrasound shows canine abdominal organs and can detect if one or both adrenal glands are enlarged or if a tumor is present on one side. It can also detect if there are metastases to other organs from a tumor.
An ACTH stimulation test may also be used to distinguish between pituitary-based disease versus adrenal-gland Cushing's. It is also used to assess the efficacy of treatment once begun on replacement.
Cushing Syndrome Canine Treatments
If a dog has Cushing's syndrome that is determined to be due to a primary tumor of the adrenal gland, surgery might be an option. However, keep in mind that if it is has spread to other organs, it will do relatively little to prolong his or her life and medication might be the best option.
Even if the tumor has not spread to other organs, it is quite possible as well that it can recur so again, mediation of the condition with medication is still a relatively expedient option as well as being more cost effective. It's always best to consider the age of your dog also and if the risks of surgery outweigh any potential benefits, medication options would always be better and less stressful to your pet.
The most common drug is trilostane (Vetoryl). Mitotane (Lysodren) is an older drug that vets do not use as much. It causes many side effects, but it may cost less.
Vetoryl was approved by the FDA in 2008. It is the only drug approved to treat both kinds of Cushing's in dogs, pituitary and adrenal dependent. It works by stopping the production of cortisol in the adrenal glands. It should not be given to a dog that is nursing, has liver or kidney disease or is being treated for heart disease of some type.
The drug can have side effects of lethargy, diarrhea, vomiting, and lack of appetite. As with any drug, it can have serious and lethal side effects such as total collapse, severe dehydration or depletion of electrolytes, bloody diarrhea, and other fatal consequences.
One other drug, Anipryl (selegiline), is an FDA-approved medication that can treat Cushing syndrome in dogs, but it is only used to treat the uncomplicated, pituitary-dependent variety of Cushing's.
If medications are used, there is constant monitoring required. The dog needs regular checkups and blood tests to make sure that the treatment is working.
Iatrogenic Cushing Syndrome
Another type of Cushing disease is called iatrogenic, which means that it is caused by something else.
Giving a dog high-dose steroids for other conditions such as inflammatory arthritis or other medical conditions can subsequently produce Cushing syndrome. The treatment options in this case usually involve a gradually tapering of the steroids to hopefully reduce the Cushing syndrome.
What If I Don't Treat My Dog's Cushing Syndrome?
About 100,000 dogs per year are diagnosed with Cushing's. Generally speaking, a dog with Cushing syndrome will live about as long as he or she will if not treated for the disease. It usually does not prolong the dog's lifespan.
However, dependent upon the symptoms of course, it may be preferable to treat the dog if the symptoms are severe enough, such as constant urinary accidents, extreme hair loss, fatigue, etc.
As in all pet diseases, we as their human caretakers have to decide if the treatment far outweighs the benefit to our beloved pets and if it is financially feasible for us to try and prolong their life or relieve their symptoms. Sometimes the treatments can also produce more problems than merely accepting the outcome of our pet's medical condition and allowing them to live out their remaining time without complications.
Two Sides of the Coin
The polar opposite of Cushing syndrome is Addison disease. This occurs when there is hypoadrenocorticism rather than hyperadrenocorticism. There is not enough corticosteroid secretion from the adrenal gland and there can be similar symptoms to Cushing's with the exception that the symptoms are usually much worse.
Symptoms can also include vomiting, diarrhea, weight loss, shaking, low temperature, weakness, dehydration, bloody feces, and pain in the abdomen. Kodi (the beautiful fellow at the beginning of this article) suffered from this disease and was diagnosed with it at 5 years of age when he went into near collapse just out of the blue.
He was treated with high-dose steroids by injection and in pill form and had to be constantly monitored. We were told that he would most likely respond if he was going to and do very well, but he would experience a very quick decline once his body could no longer absorb the steroids that we were replacing for him.
He lived another 5 years, so in his case, I think the treatment was worth it. However, he did literally tank overnight and went into total collapse, which was very painful to live through for us.
Diets for Cushing's in Dogs
Some of the recommended dietary approaches for a dog with Cushing's include:
- Low-fat diet - staying away from high fat fish products, etc as the dogs usually have increased appetite anyway and may have extra fluid retention
- Diets rich in potassium-containing foods
- Low-fiber diets as it is harder for these dogs to digest foods - shredding vegetables and fruits is a good way to give them fiber but keep it at a low level
- Natural foods - keep to as natural a diet as you can afford or even make your own food for your pet - the less additives and preservatives the better
- Raw diets - some vets and breeders recommend a raw diet as these keep sodium, fiber and carbohydrate levels low
It is interesting to note that Cushing syndrome is on the rise in dogs.
Cushing Syndrome in Other Animals
You will find some incidence of Cushing syndrome in the following animals:
- Guinea pigs
- Humans - more common!
In cats, it is fairly rare and in horses as well. Any animal that has adrenal glands could develop Cushing syndrome, though it is again, highly more common in dogs it seems than other animal species.
© 2017 Audrey Kirchner