I wrote this article because Cushing’s disease in dogs is often over-diagnosed.
Over-diagnosed is a euphemism for “your dog never had it in the first place.” And that’s a problem.
My goal? To give you the facts on how the testing procedure for Cushing’s disease works and what exactly vets are looking for. This should help save unnecessary expenses and worry.
So it’s important that we fully understand this disease.
What Is Cushing’s Disease In Dogs?
Cushing’s disease is an endocrine disorder of middle aged and older dogs. It’s the result of the overproduction of cortisone by the adrenal glands. These are tiny glands the size of a pea located on each kidney.
Normally, your dog’s pituitary responds to stress by producing something called ACTH. This stimulates his adrenals to produce more cortisol/cortisone. In Cushing’s disease, really high levels of cortisone hormone are produced continually.
Cushing’s disease results from three possible situations:
- A dog will have a microscopic benign tumor of the pituitary gland. This tumor overproduces ACTH. This stimulates the adrenal glands to produce too much cortisone. About 85% of Cushing’s cases in dogs are due to a pituitary tumor.
- Cushing’s disease is caused by a tumor in the adrenal gland that’s busy secreting too much cortisol. This is the case in about 15% of dogs.
- The third scenario occurs when a veterinarian prescribes excessive steroids as a medication. With NSAIDs (non-steroidal anti-inflammatory drugs), the incidence of this is waning.
And when it comes to Cushing’s disease in dogs, there are two problems to contend with:
- Tests that determine if your dog has Cushing’s disease are expensive and can be unreliable.
- One commonly used drug to treat Cushing’s, Lysodren, will destroy your dog’s adrenal glands. This just compounds the problem created by an incorrect diagnosis.
Let’s start at the very beginning, using a typical experience that might very well happen to you and your dog. Let’s name your imaginary dog Spot. Spot is over six years old and you take him in for his annual examination. He gets his annual Wellness Profile: a blood test. Spot has none of the symptoms of Cushing’s disease. He’s not drinking a lot or urinating a lot. He doesn’t have a sagging, bloated, pot-bellied appearance or excess panting. He’s not extra hungry or stealing food, hasn’t gained weight and he’s not weak on his hind legs, having no loss of muscle mass. His coat is beautiful and thick with no thinning of his fur and he has no areas of pigmented skin. He never gets an infection.
Spot has one thing and one thing only: elevated alkaline phosphatase. This is a liver enzyme and if it’s 2 to 3 times the normal range, Cushing’s disease is often pegged as the likely problem.
But any disorder causing endogenous stress can cause high alkaline phosphatase in dogs …
Testing For Cushing’s Disease In Dogs
Cushing’s disease seems to be on every veterinarian’s mind these days. Because of this, many screening tests are recommended to diagnose Cushing’s disease. These tests are relatively reliable if there are signs and symptoms as well as lab abnormalities.
But what if these same tests are used on animals that aren’t showing these signs and symptoms? False positive results can occur.
In addition, these tests are done at the veterinary hospital. That has impacts too. The dog is caged and the stress of hospitalization alone may cause a false positive result. Even the suggestion that a dog will wind up at the vet is enough to start the dog’s adrenals working overtime.
Because of its sensitivity, many vets consider the Low Dose Dexamethasone Suppression Test the best option. The problem with this test is it gives too many false positive results. As I said before, the stress the dog is undergoing will have a definite influence on the test results. Being locked in a cage and having blood drawn is definitely enough stress to create a false positive.
Another test, the ACTH Stimulation Test, is a popular screening test. I can’t tell you why. In general, this kind of test would be used for hypofunction, not hyperfunction, of the adrenal glands. This test misses many animals that have the disorder. I’m talking typically 20% to 30% of dogs with pituitary abnormality and 50% with an adrenal tumor.
These tests should only be used when the animal has the clinical signs of the disease. These are all the signs I mentioned above that Spot didn’t have.
There’s an excellent test you can do on your dog’s urine called a Cortisol-Creatinine Ratio Test. This test is very useful for ruling out Cushing’s disease; it has an accuracy rate of 90%. The urine has to be taken at home and the dog can’t be stressed out. Don’t even let him know that he might be going to the veterinarian’s office later on that day!
When you bring the urine sample for testing, ask the veterinarian to do a urine specific gravity. A urine specific gravity of less than 1.025 is consistent with Cushing’s disease. Dogs with a urine specific gravity greater than 1.025 are less likely to have Cushing’s.
By far, the most accurate, safe and effective method of diagnosing Cushing’s disease is the Cortisol Creatinine Ratio on an unstressed urine followed by an ultrasound.
So let’s look at this scenario. Spot has none of the signs and symptoms of Cushing’s disease. He has a high alkaline phosphatase. His cortisol creatinine ratio is elevated. What do you do? The best thing to do is find a specialty clinic that has a radiologist who does ultrasounds. Ask for a full abdominal ultrasound and have the doctor check and size both adrenals. If they’re normal in size, and your dog has none of the symptoms, it’s very likely your dog doesn’t have Cushing’s disease.
What About Atypical Cushing’s Disease?
There’s another misunderstanding called atypical Cushing’s disease. I’m convinced that a dog diagnosed with Cushing’s without corresponding symptoms doesn’t have the disease.
While there is such a thing as atypical Cushing’s disease, it’s not what most people think it is. About ten years ago, veterinarians at the Royal Veterinary College in England observed dogs that had all the
- Were drinking a lot of water
- Were urinating a lot
- Had urine specific gravities below 1.025
- Had pot-bellied appearances
- Showed muscle wasting
- Had weakness in the hind legs
- Had ravenous appetites and excessive panting
But their Low Dose Dexamethasone Suppression test and ACTH Stimulation tests came back normal.
And they all got better on Lysodren.
So these vets did some excellent research. They found that every dog had an elevated sex steroid called 17-hydroxyprogesterone. This was thought to be a marker or possibly the cause of all the symptoms of Cushing’s disease. Yes, these dogs with atypical Cushing’s disease had all the symptoms of the disease. But in the end a different hormone was causing these symptoms.
Facts About Cushing’s Disease In Dogs
It’s important to know all the facts about Cushing’s disease.
This disease is presently being diagnosed at earlier stages in life. However, a dog should still have some of the symptoms and a low urine specific gravity to consider it.
Both Trilostane and Lysodren are detoxed by the liver. In fact, it’s clearly stated that you shouldn’t give Trilostane to a dog who has kidney or liver disease. So there’s no good reason to place an animal with a liver problem and not Cushing’s disease on either of these drugs.
I wanted to bring you the very best information on Cushing’s syndrome, I spoke with Dr Rhett Nichols. Dr Nichols is a world renowned expert in endocrinology. He said:
“I believe these tests are reliable if used properly. A major point that should be made is that any screening test for any disease should only be applied to a population of animals/people where it is likely they have the disorder based on history, physical exam findings, and lab work. If a screening test is applied to animals where the disorder is unlikely, false positives (outliers) are going to occur. Bottom line? The screening tests are not bad, but their use in certain situations (eg high ALP with no clinical signs, sick animals with no signs consistent with Cushing’s) is questionable.”
What if your dog really does have Cushing’s disease? Is there anything holistic you can do?
I’ve used homeopathic ACTH with some slight success and Chinese herbs with great success.
The most effective Chinese herbs I’ve used, from the Chi Institute of Chinese Medicine, are:
- Rehmannia 11
- Rehmannia 14
- Ophiopogon Powder
- Liver Happy
You can get these herbal combinations from a variety of Chinese herb companies.
I apologize for the rather clinical disposition of this article. I wanted you to know the facts and understand how the testing procedure for Cushing’s disease works. This info will help save unnecessary expenses and worry. Both pickles and Cushing’s disease can make one thirsty but there’s no need to be in a pickle with Cushing’s.