Does My Mini Schnauzer Have Cushings?

[djalbo]

Thank you for stopping in. My 11 1/2 year old mini schnauzer, Cooper (as in Mini Cooper!) was diagnosed with diabetes (541 glucose) in early December when he got very skinny (down to 15 lbs) and became very lethargic despite eating and drinking excessively. Our Vet prescribed 3 IUs of Vetsulin which didn't help much so we went to 5 IUs. Even that didn't seem to help so we thought maybe something else was going on besides diabetes. So last week we ran a Low Dose Dexamethasone Supression (LDDS) test to see if maybe Cooper had Cushings disease as well and here were the results:

Initial Cortisol Sample: 5.6, Range 1.0-5.0 mg/dl

4-hr Cortisol Sample: 4.1, Range 0.0-1.4 mg/dl

8-hr Cortisol Sample: <1.0, Range 0.0-1.4 mg/dl

Based on these results, my vet seems to think that Cooper is Cushingoid but I am not so convinced since my understanding is that the 8-hr sample should be the primary indicator. Then there is the mini schnauzer factor which I understand may give conflicting results because of his breed. In any event, it was suggested that I post Cooper's results here to see what members thought since there is no better advice than from those who have had their own experience.

I should also note that Cooper went blind suddenly in February '16 though he has been pretty healthy since then until this winter. Thank you for any input you can provide and I would be happy to answer any questions you think may be relevant as well!

[labblab]

Hello and welcome to you and Cooper! We are so glad you've joined us. In answer to your primary question, no, I do not believe these LDDS results are consistent with Cushing's. I can give you a multitude of citations, but the bottom line is that you are correct: it is the 8-hour value that is solely responsible for establishing the overall diagnosis of Cushing's. The initial baseline value and the 4-hour value only become significant if the 8-hour value is elevated above the normal range (which Cooper's is not). If the 8-hour value is high, then the other two are examined to see whether or not they fit a pattern that would support the likelihood that it is a pituitary tumor that is the basis for the Cushing's. The lab report ought to specify these diagnostic criteria.

Also, I am unaware of any breed differences in terms of LDDS interpretation. Have you read something about this being the case? Overall, I would want to know more as to why your vet is judging this result to be consistent with Cushing's.

A "negative" on an LDDS is generally quite trustworthy since it is the more "sensitive" of the two diagnostic Cushing's blood tests (less likely to miss diagnosing Cushing's in a dog who truly has the disease). However, you could always opt to perform an ACTH stimulation test, the alternative diagnostic blood test, just to see whether you'd obtain a positive result on it. Since the LDDS is a suppression test and the ACTH is a stimulation test, they are measuring two different diagnostic parameters. I can tell you more about that if you're interested. However, the bottom line for now is that Cooper's LDDS result is negative for Cushing's.

I understand that you are having difficulty regulating his glucose level right now. How about any other external symptoms such as the excessive thirst and hunger? How are his skin and coat doing?

Was the cause of his sudden blindness ever determined? I know that there are a variety of possible causes, including retinal bleeds (from high blood pressure) or diabetic retinopathy. But those conditions should be diagnosable. There is another puzzling condition called SARDS which we are aware of on this forum because dogs who suffer from it often present with certain symptoms identical to Cushing's alongside sudden blindness. But once again, that eye condition can be diagnosed by a specialized eye exam. So I'm just wondering whether a cause for Cooper's blindness has been uncovered.

OK, I'll go ahead and stop for now! By any chance, was the recommendation to come here made by our sister forum, k9diabetes.com (http://www.k9diabetes.com/forum/)? If not, I'd encourage you to go ahead and register over there, as well. The format is identical to ours, and you'll receive some wonderful advice and support re: the diabetic side of things.

Marianne

[labblab]

Just wanted to come back and add another resource for you. It is a great article about the complexities of diagnosing Cushing's in diabetic dogs authored by noted veterinary endocrinologist, Dr. Mark Peterson. You'll see that one of the key issues is whether or not a dog is truly demonstrating insulin resistance. Per Dr. Peterson: "We define insulin resistance as doses greater than 2.2 U/kg/injection to control hyperglycemia..."

Mind you, I know next to nothing about insulin dosing or management. But since Cooper weighs roughly 7 kg, I'm thinking you would need to be clear up to almost 14 units to be exhibiting insulin resistance? (Although I also don't know whether Vetsulin is formulated differently from other insulins). Anyway, this is a question that the diabetes forum can definitely help you with. So here's the link.

http://www.endocrinevet.info/2012/01/q-diagnosing-cushings-disease-in-dogs.html

[molly muffin]

Hello and welcome from me too.

I wouldn't say your boy is cushings at this point, based on That LDDS test. Marianne gave some good reasoning on why that isn't positive.

I'm not an expert in diabetes either, and leave that to the k9diabetes group, but from what I understand, your dog isn't yet resistant and I've also been told that some dogs end up having to try different types of insulin till they get the one they respond best too.

[djalbo]

Thank you for adding to the discussion. Every iota of information is valuable when you're new to this and your dog can't speak for him/herself!