hyperthyroid?


sun_hair2002 <georgeag11@...>
 

My horse (not previously diagnosed as cushingoid) had her thyroid tested this week. She was
exhibiting an intolerance to exercise, and had stopped sweating (we're in Floirda). Her T-4
was normal, but T-3 was rather elevated. My vet is perplexed, and has offered no solutions
to her difficulties, other than to give her more food and more electrolytes, and test her agina
in a month (she ran the bloodwork twice to be sure it wasn't an error).

I couldn't find any information on treating hyperthyroidism in the files, or in the archives.

Can anyone offer any insight into what I need to consider?


Jane <kohpoh_th@...>
 

You can check the files for anhydrosis. They should give you a lot
of information on this condition which is most often caused by stress
in some form and probably a feed imbalance too.
Jane in Thailand--- In EquineCushings@..., "sun_hair2002"
<georgeag11@...> wrote:

My horse (not previously diagnosed as cushingoid) had her thyroid
tested this week. She was
exhibiting an intolerance to exercise, and had stopped sweating
(we're in Floirda). Her T-4
was normal, but T-3 was rather elevated. My vet is perplexed, and
has offered no solutions
to her difficulties, other than to give her more food and more
electrolytes, and test her agina
in a month (she ran the bloodwork twice to be sure it wasn't an
error).

I couldn't find any information on treating hyperthyroidism in the
files, or in the archives.

Can anyone offer any insight into what I need to consider?


sun_hair2002 <georgeag11@...>
 

Thanks for your response, Jane. I did check the anhydrosis files
prior to having the bloodwork done, which is why I wanted the vet
to check her thyroid levels. However, the files suggest that this is
normally a problem with HYPO rather than HYPER thyroidism,
wherein her T3 should have been low, rather than high.

However, one statement in the files did seem possibly relevant: "as
I understand it, too much TSH (thyroid stimulating hormone) is
produced which leads ultimately to thyroid exhaustion, the thyroid
ceases to respond to the TSH and therefore is no longer producing
sufficient thryoidhormones. The key with that disease is to slow
down the pituitary's production of TSH (and other hormones) so
that the thyroid can recover and produce the correct amount of
thyroid hormones."

The vet suggested (before we had the results back) that if they
came back without answers, we might test her ACTH. Does the
above statement suggest that her ACTH might be the root cause?
Does it make sense to have the vet back out for ad'l bloodwork?

--- In EquineCushings@..., "Jane" <kohpoh_th@...> wrote:

You can check the files for anhydrosis. They should give you a lot
of information on this condition which is most often caused by stress
in some form and probably a feed imbalance too.


Joan and Dazzle
 

Hi Sun Hair,

Our case histories appear to be down, so if you've posted the
information in your case history, I apologize for not reading it.

The only way that you can have better information as to what's going
on is to get a better diagnosis. Although thyroid abnormalities
sometimes are the issue, usually you see them in response to
something else going on.

If this were my horse, I would do a couple of more tests. They would
be ACTH, insulin and glucose. They can all be done from one blood
pull, about 2-4 hours after a low sugar/starch meal.

The ACTH will tell you if you have cushings going on. Some horses
are cushings without the long fur. Some horses' first symptom of
cushings is laminitis. We've learned to do the blood work to help us
diagnose it.

The insulin and glucose will tell us if your horse is insulin
resistant. It will have many of the same symptoms as cushings and
some vet still confuse the two.

Cushings is treated with meds - usually pergolide. Insulin
resistance is treated with diet.

This will give you a better picture on what's going on with your
horse. Both of them usually affect the thyroid levels. Frequently,
when you fix an underlying cause to your metabolic issue, the
thyroid levels return to normal.

Do you have ACTH, insulin or glucose numbers? If not, we have a file
that tells the vet how to pull blood. Many of us use Cornell for
the lab.

Anhydrosis is also seen in many different metabolic conditions. But
again, if the underlying issues are not addressed, it may be very
difficult to fix the sweating issue.

Joan and Dazzle

--- In EquineCushings@..., "sun_hair2002"
<georgeag11@...> wrote:

My horse (not previously diagnosed as cushingoid) had her thyroid
tested this week. She was
exhibiting an intolerance to exercise, and had stopped sweating
(we're in Floirda).
Can anyone offer any insight into what I need to consider?


Eleanor Kellon, VMD <drkellon@...>
 

--- In EquineCushings@..., "sun_hair2002"
<georgeag11@...> wrote:

Her T-4
was normal, but T-3 was rather elevated.
If T4 is normal, she's not hyperthyroid. There are a few things that
could produce this picture:

Iodine deficiency: When iodine intake is not optimal, the deiodinase
enzymes in the thyroid will preferentially produce T3 (the active
form), "recycling" what thyroid hormones they have. T4 is usually low
but could be low normal. Low level nitrate toxicity (from high levels
in water or diet) or perchlorate exposure (Duval county in Florida
has had a problem with this) could magnify a problem of low or
borderline iodine intake. Nitrate is a common contaminant of well
water, originating from nitrogen containing fertilizers. Excessive
use of manure as a fertilizer can also cause high nitrate in hays, as
can drought or anything else that stunts the growth of the grasses.

Cold weather (probably not your problem!) causes elevated T3 with
normal T4. The elevated T3 uncouples ATP production in the
mitochondria, making it inefficient with the result that more food
energy is "wasted" as heat.

Feeding - both responses to a single meal and the basic composition
of the diet, can have significant effects on thyroid hormone levels.
See:

http://jas.fass.org/cgi/reprint/78/12/3107

Exercise has also been reported to increase T3 while T4 remains the
same. (Short term exercise - endurance rides are different.)

It's very difficult to figure out what is going on in horses because
TSH (thyroid stimulating hormone) testing is not commercially
available for horses. You could get further information by running
Michigan State's "premium thyroid profile"

http://animalhealth.msu.edu/Bin/Catalog.exe?
Action=Test&Name=thyroid&Species=Equine&Id=2175

Which includese free T4 and free T3 as well as the total T3 and T4.
It's only the free forms that are biologically active.

Eleanor


sun_hair2002 <georgeag11@...>
 

Thanks, Dr. Kellon, and Jane, for your posts. I'll have the vet back out shortly for the ACTH,
glucose and insulin tests.

--- In EquineCushings@..., "Joan and Dazzle" <horsies4luv@...> wrote:

If this were my horse, I would do a couple of more tests. They would
be ACTH, insulin and glucose. They can all be done from one blood
pull, about 2-4 hours after a low sugar/starch meal.