Advice for a frustrated sheltie mom

[ConnieM]

My name is Connie and I am new to the forum....seeking advice! My 6 year old male sheltie, Murphy was diagnosed with pit. cushings. I have picked up his trilostane and plan on beginning treatment this weekend. However, I am not entirely onboad yet for the following reasons:
1. he started taking phenobarbital 2 years ago for localized seizures (hind quarters only). responded well to the med and is still taking it.
2. had a break through seizure about a year ago and the vet did some tests and diagnosed him with thyroid disease. put him on thyroxine. he was drinking so much water, peeing all the time and panting. I thought it was just side effects from meds. about 2 months ago he wasn't well so I took him to the vet and he told me his sodium and potassium had bottomed out so he stayed 24 hours at the vets office with iv's.
3. vet never would / could tell me what caused this...other than to much water. I told the vet I noticed the water intake accelerate once he began the thyroid meds and could I take him off of it to see how he would do. His answer was NO. I asked him if he could possibly have cushings....again, NO. but no further tests.
4. took Murphy back to a trusted vet I used years ago and she felt he probably has cushings. told me to take him off the thyroxine - which I did - and he seemed like my old Murphy for a couple of months. thought I had found the answer as the vet told me a dog on pheno could test false positive for thyroid disease.
5. Murphy began showing all the old symptoms (thirst, urination and panting) so I took him to the vet and she ran the low dose whatever test and says he has pit cushings.

my dilemma....could he have had cushings all along and that was what triggered his seizures? could he really have a thyroid issue in addition to cushings? and if a dog on pheno can test false positive for thyroid disease, how can I ever know if he has a thyroid issue?

I'm at a loss. I will do whatever is within my power for him, but I feel like I'm all over the place with what is actually the problem(s) and I don't want to put him on this strong trilostane if he doesn't need it.

Any advice / experience is greatly appreciated!!

Connie

[Harley PoMMom]

Hi Connie,

Welcome to you and Murphy, from reading your post I understand your frustration and hopefully once we all put our heads together we can get a better picture of what is going on with sweet Murphy.

Phenobarbital can most definitely can skew the results on a thyroid test and also the low-dose dexamethasone suppression test (LDDS) which is considered the "gold standard" test used for diagnosing Cushing's. Was Murphy's thyroid levels checked while he was taking the thyroid medication? If his thyroid levels were too high from the medication this will cause a dog to drink/urinate more. Increased drinking/urinating can be attributed to other non-adrenal illneses such as an UTI or diabetes, have they been ruled out? Phenobarbital in itself can make a dog drink and urinate more.

Could you get copies of all the tests that were done on Murphy and post those results here? With respect to the chemistry/CBC blood panel you need only to post the abnormal levels along with their normal ranges.

Is the increase in drinking/urinating and panting the symptoms that Murphy is displaying? The most common symptoms from Cushing's are a ravenous appetite, skin/hair issues, pot-bellied appearance, exercise intolerance, and difficulty or unable to go up steps or jump on furniture, does Murphy have any of these? The medications used for Cushing's do not to cure it, the sole purpose of treatment is to remedy problematic symptoms which is why strong symptoms play a huge part of the diagnosis for Cushing's.

Cushing's is probably the most difficult canine disease to diagnose. Physical symptoms associated with Cushing's are shared by many other diseases, blood and urine abnormalities are shared with other other diseases and the diagnostic tests to measure circulating cortisol are flawed and can yield false positive results in the face of non adrenal illnesses or even stress. All of these things make it very challenging to correctly diagnose Cushing's which makes it one of the most misdiagnosed canine diseases. There isn't one test that can accurately identify it so multiple tests are needed to validate a diagnosis for Cushing's.

I am sorry for the reasons that brought you here but sure glad you found us and we will help in any way we can.

Hugs, Lori

[labblab]

Hello and welcome from me, too! I'm so glad Lori has had a chance to talk with you already, and I just want to "second" her warning about the LDDS test. My understanding is that, for dogs taking phenobarb, the ACTH stimulation test should be used as the diagnostic for Cushing's as opposed to the LDDS.


Phb treatment can alter thyroid and low dose dexamethasone suppression (LDDS) tests. Phb is associated with decreased total serum T4 and Free T4, but normal T3 and normal or increased TSH concentrations. This may be due to such factors as the increased clearance of T4, increased biliary excretion of T4 as bile flow increases, and increased peripheral deiodination of T4 to T3. Thus, while Phb treatment may mimic hypo-thyroidism biochemically, the patient should not appear clinically hypothyroid, unless there is concomitant hypothyroidism. Phb also enhances the clearance of dexamethasone, which may lead to a false positive (escape from suppression) on LDDS testing. However, Phb does not affect the cortisol response to ACTH stimulation or endogenous ACTH concentrations. Therefore, when testing for Cushing’s disease in dogs receiving Phb, the ACTH stimulation rather than LDDS test should be used.

http://www.canine-epilepsy-guardian-angels.com/antech.htm

Under these circumstances, I'm not sure I'd feel comfortable beginning Cushing's treatment, yet, either. It seems as though there are still remaining unanswered questions, given the return of your dog's symptoms. Is Cushing's really an accurate diagnosis, or may your dog instead still be suffering from primary hypothyroidism?

My own Cushpup was a Lab who also exhibited low thyroid readings. He did receive ongoing thyroid supplementation, and unfortunately he passed away before we could determine whether his hypothyroidism would have ultimately resolved with the Cushing's treatment. I now have a nonCushpup Lab girl who suffers from seizures of unknown origin, and who has been successfully taking phenobarb for about six years. When she first started seizing, I actually hoped her thyroid panel would come back low since hypothyroidism is known to cause seizures and the treatment for hypothyroidism is so simple. But her thyroid was within normal range, and it has remained within the low end of normal since then, even though we realize the phenobarb may be skewing her results. Since she doesn't exhibit any outward symptoms of hypothyroidism, however, we have not worried about requesting more involved thyroid readings.

But in your dog's case, she IS exhibiting symptoms. So here are a couple of quick questions. First, when is the last time your dog's phenobarb level was checked? As I'm guessing you already know, the drug itself can cause many of the same symptoms as Cushing's, especially if the dose is too high: excessive thirst, urination, and appetite. The level of phenobarb that accumulates in the bloodstream can change over time, so you really do have to periodically check the blood to make sure the dosage doesn't need to be changed.

Secondly, you are right that it is much more difficult to properly evaluate thyroid function for dogs taking phenobarb. But there are veterinary labs which perform specialty services, and it may be useful to have your dog's thyroid level re-evaluated by a lab that has particular expertise in thyroid analysis. One such veterinary lab is the one at Michigan State University. They will accept and analyze blood samples from all over the country. It is possible that they, or another specialty lab, may be able to offer more in-depth interpretation than you are receiving through your vet's general lab service. Just a thought, because seizure activity can definitely be caused by low thyroid.

When pituitary tumors that cause Cushing's expand to a larger-than-usual size, it is possible for them to put pressure elsewhere in the brain and for seizures to result. However, if your dog's seizures began fully two years ago, I'd be less inclined to suspect a brain tumor as the culprit. I'd think that a tumor large enough to cause seizures would have advanced much farther by now, with additional evidence of brain damage.

So if it was me, I would not yet feel comfortable starting Cushing's treatment without these things having been done:

Confirmation that the level of phenobarb in your dog's bloodstream is neither too high nor too low (this is checked via blood test).

Completion of a full thyroid panel by a lab with special expertise in that area.

If both of the above check out OK, then I'd want an ACTH stimulation test performed instead of the LDDS. The LDDS simply cannot be trusted in a dog taking phenobarb.

Marianne

P.S. I apologize because I just now realize I called your dog a "she" instead of "he" all through my reply. I'm very sorry, and will do better next time around! :o

[ConnieM]

Harley PoMMom and lablab......thank you so much for your advice.

I do have Murphy's phenol levels checked on a regular basis...but I can't tell you what they are. The vet basically says everything if fine...keep doing what you're doing.

When he was on thyroid meds his levels were also checked regularly. Again, keep doing what you're doing.

I will get copies of his records, levels and also the results of his cushings disease test and share with you!

I am alone in making this decision so I just needed someone to "talk" it over with me.

I am NOT going to begin the treatment this weekend as planned. I need more info.

Also....he does not have fur issues at all. Beautiful, full coat.

Just the excessive thirst, urination, panint and weight gain (gained 7.5 pounds within 2 months after I took him off thyroxine....which makes me lean more toward thyroid issue).

Thanks ever so much!!!!!!!!!!!!!!

[molly muffin]

Marianne and Lori both know more about phenobarb and what it might cause symptom wise, so I'll go with a welcome to the forum!

I don't blame you for not wanting to start cushing meds till you get to the bottom of the symptom issue.
I would want to know that the current phenobarb levels and thyroid levels are within normal range. If they aren't they could be part of the problem and if they are, then likely they aren't.

If you do end up starting cushing treatment, trilostane should be given at no more than 1mg/1lb to start off with. You want to go low and slow and make sure of how he will react to the medication first.

It is possible he has had cushings and does have, it is known as a slow progression disease and also one of the hardest to diagnose unfortunately.

But you are well on your way to sorting this out. First step is eliminate the other possibilities.

[Angus2223]

Hi Connie,
I'm new here as well, but have been dealing with Pituitary Dependent Cushings since last July. Are your dog's liver enzymes high? GGT, ALP and ALT were all very high, with GGT being extremely high in my dog when her cortisol levels were extremely high. ....... Just putting some thoughts together here for you too. You're not alone & all of these ladies are absolutely wonderful & their knowledge is truly outstanding!

Jessica