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  Discussion on Dex Suppression and Laminitis
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New Member:
Cnbreb

Posted on Friday, Jan 20, 2006 - 11:54 pm:

I have a 27 YO Qh mare, who exhibits slight muscle wasting and evidence of chronic laminitis. We have been actively treating her for over a year to manage the laminitis with no luck. She is not growing any foot which is making it difficult to keep her comfortable. She is currently in Natural balance aluminum shoes. I have been doing some research on Cushings and was thinking about having her tested. Currently two vets are involved, both with differing opinions about the dangers associated with the use of Dex on foundered horses. In order to get a script for pergolide from my regular vet, I have to have the horse screened/tested. The vet wants to do the dex suppression through a northern lab. I looked on line and found information on the Cushings screen through BET labs in Kentucky who indicated that dex suppression is not recomended for laminitic animals. I'm concerned as the mare's radiographs show rotation and loss of bone (i.e., dorsal surface of pedal bone is curved) and I really don't want her to have a serious relapse. Which test has the lowest risk with the highest sensitivity if the dex test is too risky?
Member:
Shirl

Posted on Saturday, Jan 21, 2006 - 12:17 am:

Carolyn, Ask your Vet to do the ACTH test, It's one blood draw. Safer than the Dex, particularly if your horse is showing symptoms of lamitis. Also log on to EquineCushings@Yahoogroups.com. Loads of info you need NOW. Diet, Trim and Diagnosis is very improtant. } Shirley
Moderator:
DrO

Posted on Saturday, Jan 21, 2006 - 8:15 am:

Welcome Carolyn,
The problem is the ACTH test has been shown in carful experimentation to not be a accurate test for Cushings. Concerning the dex-suppression this has been shown to not represent much threat to worsening laminitis. Both of these issues and other important information on the diagnosis are discussed in detail in the article associated with this forum.
DrO
New Member:
Cnbreb

Posted on Saturday, Jan 21, 2006 - 8:41 am:

Dr. O--
Thanks for the post. If I'm understanding you correctly, the dex shouldn't cause a secondary flare-up or significantly worsen it? I read the article, but again conflicting opinions can really put owners in a quandry. I'm aware of the dangers of dex, but thought it was generally with prolonged use. The basis for my regular vet's opinion. However, the other vet indicated that horses can founder from a single dose and wouldn't recommend exposing her to any steroid given the X-rays. I don't know if the information is pertinent, but she does not appear to be actively foundering ( X-rays taken 10 months apart show no significant changes) and unfortunately we don't even know how recent the remodeling of the pedal bone occurred since we have no previous films to compare them with.
My farrier's biggest concern is what is retarding the growth of the mare's hoof capsule as we a literally running out of hoof wall to "play" with. His opinion is the laminitis has to be secondary to something else, thus leading back to the test. I can post the history if it helps, along with any general health profile you would need. I know you can't give a prognosis without seeing the mare, but it would be nice to have a fresh set of eyes look at the profile.
Thanks again!
CB
Moderator:
DrO

Posted on Sunday, Jan 22, 2006 - 3:52 pm:

In what was a direct study of this exact question a number of Cushing horses with active laminitis were given the dex-suppression test none or which had exacerbation of the clinical signs. I don't have the report available as we are traveling right now, but it was presented at an AAEP meeting quite some time ago and I have seen nothing to contradict it nor have I ever had such a problem. In addition the case for dexamethasone induced laminitis even in the case of very large doses or prolonged use is weak. Not only clinically is it hard to find clear cut cases but experimentally you cannot induce founder with large or prolonged doses. BET is basically covering thir bets with this statement because nobody can say that after giving the test your horses founder won't worsen horribly.

By all means post the information keeping it concise as possible but don't leave out anything factual and include the units and the labs normals.
DrO
Member:
wolfydoc

Posted on Tuesday, Sep 11, 2007 - 8:15 pm:

Hi DrO,
I know this is an "old" thread but I need to start it up again. I have been arguing the same stuff re: the DST with others recently and I too feel the DST should not be feared. But can you cite the articles/studies mentioned in this thread so I have some concrete info to present re: the lack of evidence that doing the DST causes laminitis? It's also very hard to argue with folks who say "but my horse or my friend's horse foundered 2 days after the test!" I realize that a temporal association does not equal cause and effect, but that is very hard to convince others of. Sites like the Equine Cushings group have people screaming this all the time and it becomes very difficult to convince clients of the lack of validity of these reports.

Also, can you give me some references showing that the DST has the highest specificity and sensitivity compared to the other tests? I know a vet who wants a study comparing the tests followed by post-mortem confirmation but I don't know if this exists. If not, what are the best studies to cite?

I would love to get with a medical journal search engine but I don't know of one that is not cost prohibitive - do you? I would give my right arm for such a thing. Any suggestions would be greatly appreciated.

Cindy Nielsen, VMD (switching from small to equine practice!)
Member:
scooter

Posted on Tuesday, Sep 11, 2007 - 8:42 pm:

Cindy I can't speak from a medical view, but from an owner that has a foundered horse I wouldn't do it either if there was even a 1/2% chance it could set off an episode of founder.

I also own an older horse that I believe has cushings and very prone to laminitis with the right triggers. From what I've read in Dr.O.'s articles usually the symptoms are pretty good at diagnosing it, and if symptoms can't be controlled try pergolide if needed. That is also what my vet told me.

Congratulations on your new career.
Member:
wolfydoc

Posted on Wednesday, Sep 12, 2007 - 1:43 am:

Hi Diane,
I totally understand your point, and I'm not saying that the test is necessary in every case. But there are horses who are not as obvious as the classic textbook case and we need to test. We need to figure out whether the horse has Cushing's or some other disease, for obvious reasons. One, so we don't neglect to give the proper treatment while putting the horse on a trial of Pergolide, and two, so we don't waste the owner's money on an unnecessary medication. Further, time and money is wasted when running tests that may have a higher incidence of false positives and negatives. I certainly want the test that will most likely give me a correct diagnosis if I'm going to formulate a treatment plan. But again, I totally understand your point. I just don't believe the Dex Suppression should be thrown out the window.
Thanks for the congrats!
cindy
Moderator:
DrO

Posted on Wednesday, Sep 12, 2007 - 1:45 pm:

Hello Dr Nielson,
The only such inexpensive (free) database I am aware of is PubMed but except in rare cases all you get is the summary, however I do find those very useful.

The problem with the question on laminitis is you are trying to prove a negative: dex does not worsen the founder. What we do have is the lack of occurence of founder in large studies where dex is administered. This includes the testing of horses suspected of PPID with the DST.

One should note that in the Diagnosis Summary of the article that the presence of consistent clinical signs, particularly hirsuitism is considered really the best diagnostic criterion. But if you are looking for a really good discussion on this see the 2006 AAEP Proceedings and the review by Schott's titled "Pituitary Pars Intermedia Dysfunction: Challenges of Diagnosis and Treatment". It says that the founder problem is "poorly documented" and though the DST is considered "the gold standard by practitioners" it is not without its problems. I think we address most of these problems in the article. Unfortunately we do not yet have a test you can absolutely hang your hat on.
DrO
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