Snow Leopard

Snow Leopard
Snow Leopard cub (7 mos old) - Cape May County Zoo

Thursday, January 27, 2011

Adrenal Disease: Too Much of a Good Thing

Aka: Hyperadrenocorticism or Cushing's disease. 

Adrenal glands are small endocrine glands located just above the kidneys. 

They are responsible for an animals response to stress, as well as regulating mineral balance in the body.

The body controls how much of the necessary compounds are released by a very well regulated feed-back system:

 So any stressor (this is not just emotional/mental stress but also physical illness which is a "stress" on the body) will stimulate this pathway to direct the adrenal glands to produce and release cortisol. 

Cortisol, while having some unhealthy effects, is absolutely essential for any healthy living organism.  Yes, you could die if when you were stuck in traffic and freaking out, you did not have a functional pituitary/adrenal axis! 

Cushing's disease is on OVERproduction of cortisol. This can be due to a pituitary problem or an adrenal problem. 85-90% is due to pituitary disease. The other 10-15% is caused by an adrenal tumor  (50% of these are malignant). We can also CAUSE this (the term "iatrogenic" is used) by giving high/long term doses of steroids. This is why so many vets truly try to avoid this unless there is no other option. 

What we first hear from clients is "my dog is drinking and urinating excessively!" In the vet world, this is PU/PD (polyuria/polydypsia).  Many times they think it's diabetes. Definitely a possibility. And in fact, we sometimes see dogs that have BOTH diseases.  

This can be a sign of other diseases as well, including kidney disease, so of course, blood work and a urine sample are the best way to get a start on figuring this all out.  

The signs you see in a Cushinoid dog are the same signs you see if you've ever treated a pet WITH steroids for something: they drink a lot, pee a lot, have a BIG appetite, and often pant and can be restless. Well, this is the same thing only it's coming from an internal source. 

Dogs who have Cushings but are also diabetic can be VERY difficult to regulate. Cortisol causes insulin resistance, hence our reason for NOT treating diabetic dogs or cats with any steroids. 

Who is at risk for Cushings? poodles, dachsunds, Boston terriers, boxers, beagles..and yes, any breed could get it.  Cats can also have this but I personally have never seen or diagnosed this in a cat. 

There is a good way to screen dogs: bring a urine sample you collect at home to your vet and they can check for the urine cortisol/creatinine ratio. Since the dog is at home and in a less stressful environment, this can be a great starting point to test. However, keep in mind that you can have a decent number of false positive (so dogs that truly don't have disease are showing a high level).  But if they are negative, they likely are truly that. 

Many dogs will also have a "pot-bellied" appearance and some loss of hair that is usually symmetrical (even on both sides of dog).

So what do we see that really tells us that your dog has Cushings? Well, the typical abnormality in the bloodwork is an elevated Alkaline Phosphatase, a liver enzyme, that is induced (or increased)  in production, when steroids are present. So if your dog is on prednisone or dexamathasone for another issue (skin, orthopedic, etc) this WILL be elevated. 

If your dog is NOT on steroids, and is NOT PU/PD, but has a high AlkPhos,  it is NOT Cushings and other diagnostics should be pursued (ultrasound, possible liver biopsy, etc). 

What we look for is a significant increase over normal (classically 4x the high normal limit). 

If we see this, this does not mean your dog absolutely 100% has Cushings. There are other blood tests that will help us truly diagnose this.

Two tests that are used are the Low Dose Dexamathasone Test (LDDT) and the ACTH stimulation test. You can see on the feedback diagram that ACTH SHOULD cause the adrenal gland to produce steroids. In dogs with Cushings, we get a LARGER response than normal. The LDDT is a great test because it allows us to actually determine if your dog's problem is pituitary vs adrenal.  Both tests are not invasive and simply involve 1-3 blood draws through the day after we give either ACTH or Dexamathasone as an injection.
If we think it is an adrenal issue, we may recommend an ultrasound to see if there is a tumor of the gland and how invasive it is. 

Once we come to this as a diagnosis, there are several medical options to treat this. Untreated disease will  progress and carries a very poor prognosis. The treatments include oral drugs, such as Mitotane and Trilostane. Mitotane works by destroying some of the adrenal tissue. Yes, there is a risk of getting rid of too much,  so many vets will either make sure you have some prednisone to give or will direct you to give a low dose during treatment or at least, during stressful events (grooming, boarding, etc).  Trilostane works by blocking conversion of compounds TO steroids. Once you stop giving it, things revert to normal. This has become the main treatment of choice. Some vets will also use Anipryl (a drug that came out to treat Canine Cognitive Dysfunction aka "doggy Alzheimers"). Studies have shown this drug to be minimally effective. I had one dog that did superb on it. It seems a bit "safer" and was before I had access to Trilostane, which was only approved for us in the US in the past few years.

No matter the treatment, it is not cheap. It can run approx $100/mo to start..and the larger your dog is, the more costly.  

Tomorrow we'll discuss what happens when these glands don't produce what they are supposed to!

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