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  Discussion on Cortisol Ryhthm and Cushings
Author Message
Member:
Pam1

Posted on Friday, Jan 30, 2004 - 10:14 pm:

Hello Doctor,

I have a 15 year old gelding which started showing mild lameness and soreness in his work late last year as well as he had a serious colic bout. Since this time, he has been to the vet clinic three times for evaluation. After reading as much as I could on this site about Cushing's, I am more confused than ever.

The horse has always had a normal coat and sheds normally in the spring. No cresty neck - beautiful muscle tone and good weight and appetite. X-rays showed mild laminitis.

The vet I have been working with calls the horse's condition "Chronic Metabolic Disease" - but is it related to Cushings?

In his first Cushings screen his T4 was right in the middle of the "normal" range both a.m. and p.m. His Insulin was out of the normal range low both a.m. and p.m.(slighly higher p.m.) and his cortisol was on the high end of the normal range but showed no change a.m. to p.m. At that point, the vet put the horse on 1 ml of pergolide administered in the a.m. to see if the results changed after 3 weeks.

The second test 3 weeks later showed normal T4 both a.m. and p.m., Insulin right in the middle of the normal range a.m. and the low end of the normal range p.m. but this time the horse had a 26% change in cortisol(high and out of normal range a.m. to normal range p.m.) The vet then recommended an increase of 1/2 ml of the pergolide to 1 1/2 ml total administered in the a.m.

The most current test shows everything a.m. and p.m. within the normal range and a 34% Cortisol rhythm. Vet said horse should stay on current dosage of pergolide and we will test again soon.

Dr. O - I think you mentioned in another discussion some facts about the cortisol rhythm value and it's relationship to Cushing's and horse health. Could you elaborate on this and explain whether or not my horse is a Cushing's patient or not? My vet says he's not. At this point, I am having a hard time sorting things out as well as wondering if my horse will be on Pergolide the rest of his life. . . .

He has started working again and looks great.

Thanks!
Moderator:
DrO

Posted on Saturday, Jan 31, 2004 - 6:12 pm:

Hello Pam,
Unfortunately there is not enough information in your article to know if he is Cushinoid or not but we actually have an article that specifically addresses the question of the differences between Equine Metabolic Disease and Cushings. They are not the same disease though they share some common symptoms and endocrine problems. See » Equine Diseases » Endocrine Disorders »
Equine Metabolic SynDrOme (Peripheral Cushings). It think it will help you greatly with deciding which problem you have because though they have some similarities, clinically they are nothing alike.

The article on Cushings disease states, "there is so significant change in the dinural variation in cortisol in Cushinoid horses versus normal horses".
DrO
Member:
Pam1

Posted on Monday, Feb 2, 2004 - 10:34 am:

Thank you Doctor -

Might you be able to explain the value of the cortisol rhythm check and where I can find more information about this specifically? If a horse is in pain constantly, would there not be the 30 percent change a.m. to p.m.? By your last statement above, I assume Cushing horses have the normal variation of cortisol levels, a.m. to p.m.
I am still trying to understand all the articles.
Moderator:
DrO

Posted on Tuesday, Feb 3, 2004 - 9:59 am:

When you ask what is the “value” I need to know in reference to what. For instance, the “value” in diagnosing Cushinoid horses is zero. As near as I can tell the change in rhythm in response to pain has been unstudied but we do know the overall levels of cortisol rise with pain.
Member:
Pam1

Posted on Thursday, Feb 5, 2004 - 9:53 pm:

Is cortisol rhythm used as a value for prescribing Pergolide to a horse? For instance, in my horse's first test the cortisol was the same a.m. and p.m. I understood that this was the reason he was put on 1 ml of Pergolide. In the second test the rhythm was 26% which was low, prompting a 1/2 ml increase in the Pergolide. In the most recent test it was 34%. I believe normal is 30% or more difference a.m. to p.m. I believe this test is the standard Cushing's screen which includes T4,insulin,cortisol and cortisol rhythm. I could not find anywhere in the articles or information on this site that explains exactly what values in a Cushing's screen would prompt a vet to prescribe Pergolide. To be truthful, I'm not exactly sure how this medication does it's job.
Moderator:
DrO

Posted on Friday, Feb 6, 2004 - 7:48 am:

Hello Pam,
Cortisol rhythm is not a useful guide for directing therapy and when you read about the uncertainties of all of these type tests you are pretty much left with control of clinical signs being the primary factor directing therapy. For how pergolide works see, Equine Diseases » Endocrine Disorders » Cushing's SynDrOme and Pituitary Tumors » How does Pergolide work?
DrO
Member:
Skeller

Posted on Friday, Apr 8, 2005 - 10:21 pm:

Dr.O, I was unable to find the How does Pergolide work? article referenced above. I also looked under Meds. Am I missing it?

Thanks, Sandi
Moderator:
DrO

Posted on Sunday, Apr 10, 2005 - 8:17 am:

I went to the article and see it has been accidently edited out of it. I will put it back in but in the mean time, pergolide works by slowing down the release of the cortisol-like pro-opiomelanocortin (POMC)-derived peptides from the pituitary tumors.
DrO
Member:
Skeller

Posted on Sunday, Apr 10, 2005 - 11:15 am:

Computers are great but those accidental edits easily happen. Thanks!
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