Monday, February 21, 2011

Q & A: Does this Dog have Cushing's Syndrome?

I recently ran a low-dose dexamethasone suppression test on a 11-year-old male neutered Maltese with clinical features of muscle loss, thinning coat, and a pot-bellied appearance.  His serum chemistry panel is completely normal except an alkaline phosphatase activity in the thousands.  Below are the results low-dose dexamethasone suppression test, but I am confused as to what to make of them.
  • Basal cortisol:  5.1 μg/dl (reference range = 1-4 μg/dl)
  • 5-hr post cortisol:  <0.7 μg/dl (reference range = <1.5 μg/dl)
  • 8-hr post cortisol:  1.9 μg/dl (reference range = <1.5 μg/dl)
Thanks in advance.


My Response:

The interpretation would be as follows: Slightly high basal cortisol, with complete suppression of cortisol at 5 hours, followed by escape from cortisol suppression at 8 hours.

The lack of suppression at the 8-hour testing period is diagnostic for hyperadrenocorticism. The fact that the dog suppressed so well at 4 hours tells us that this dog's Cushing's disease cannot be caused by an adrenal tumor (ie, these dogs would not suppress cortisol with either the low- or high-dose dexamethasone suppression test).

The pattern of cortisol suppression at 3-5 hours followed by escape from cortisol suppression at 8 hours, as shown here in this dog, is always diagnostic for pituitary-dependent hyperadrenocorticism.

7 comments:

Penny said...

My 11.5lb toy poodle has Addisons . she is on percorten v and pred I give her 1/4 of 1mg tab. and her percorten is done by weight. she has gained lots of weight she was 5 lb when she was diagnosed 5yr ago. can she come off of prednisone. Is blood in the urine a side effect to one of these drugs . she takes her pred with a little piece of meat does she have to have more food with it I would like her off if possible. her body feels hard could it be from her meds and she floods when she pees

Dr. Mark E. Peterson said...

I'd talk to your vet about trying to stop the prednisone to see if that helps the thirst. Many dogs do fine without it, at least on most days (you might have to give a dose once or twice a week if the appetite becomes picky).

Any prednisone could predispose to a urinary tract infection so they should also do a urinalysis and urine culture too.

Dr. Mark E. Peterson said...

I'd talk to your vet about trying to stop the prednisone to see if that helps the thirst. Many dogs do fine without it, at least on most days (you might have to give a dose once or twice a week if the appetite becomes picky).

Any prednisone could predispose to a urinary tract infection so they should also do a urinalysis and urine culture too.

Janette Aranduque said...

Hi, Dr. Peterson
My Rottweiler, Skylar was diagnosed with primary Addison's May 26, 2013. She was doing ok with florinef 3 tabs twice a day and prednisone 6.25mg once a day. Four days ago, she started having diarrhea and behaviour a bit off. Electrolytes were checked today, Na 136, K 5.3---vet increased florinef to 4 tabs twice a day and same dose of prednisone. She is 31kg. Is the dosing appropriate? I think pred dose is still high, her activity level is non existent, panting, always hungry, and shedding lots.
Thank you in advance for your advise,
Janette

Dr. Mark E. Peterson said...

Yes, based on your dog's symptoms of panting and increased appetite, the dose of prednisone is probably too high. Most dogs need a daily dose of about 0.1 mg/kg so that calculates out to be about half of what you are giving now.

In addition, the Florinef also contains a great deal of glucocorticoid activity (prednisone is a glucocorticoid), so it may be that you can even wean your dog off of the prednisone completely.

I'd cut the prednisone dose in half for now, and see if that helps the panting, etc. If not, I'd go every other day with the 3 mg of prednisone and evaluate the response. There is no test to tell us how low to go, and it may be that, even if can totally stop the prednisone, there may be days when he need some (ie, if the appetite is poor).

Good luck!

Donna said...

My dog weighs 47 pounds she take shots every 4 weeks at 1.40 she takes preds twice a week at 2.5 milligrams. I'm wondering if she needs to be on Preds everyday at 1.25 milligrams. My vet says she's OK and keep her the way she is her bloodwork comes back okay. Do think 2.5 is too much. Please help

Dr. Mark E. Peterson said...

With Addison's, we generally give a low dose of glucocorticoid (Pred) every day, not twice a week. The duration of action of the drug is only; a day. So 1.25 mg per day sounds like that should work.