# cat eats and eats, doesn't gain weight thyroid?



## mimitabby (Apr 20, 2010)

Hi, I just got the results from my vet of the 'senior scan' blood test which showed that my cat has great kidneys
and liver but her thyroid reading was "a little" high.
Her reading was 7.8 and normal was between 1 and 4.5.

He wants to put her on medication, so we'll be back there next week to get her dose figured out.

anyone here have thoughts or wisdom about thyroid problems in an otherwise very healthy 10 year old cat?


----------



## laurief (Jun 22, 2008)

Here we go, another cat with hyperT and another vet who apparently hasn't provided his client with the information she needs to know about her cat's condition. Let me see if I can fill in some very important gaps for you.

It seems that many vets are not well versed in hyperT, its testing, or its treatment options. Vets simply can't be expected to know all things about all diseases in all animals, so it's up to us to become educated in the specific diseases suffered by our own animals. I will tell you here what I have learned - or believe I understand - about this disease. I have gained most of this information from the hyperT mailing list, its members, their posts and message archives, and the research papers and other educational files stored in the "files" section of the list's Yahoo website. I strongly recommend you join that list. Even if you prefer not to post, you can learn a great deal by doing searches for specific information in their message archives and by reading the uploaded files. You may also, of course, ask whatever questions you may have of the list members by posting to the list. You can read about and join the list through this link:

http://groups.yahoo.com/group/feline-hyperT/

OK now - testing for hyperT ...
The Total T4 test does not test the actual function of the thyroid gland or the degree of hyperthyroidism, if present. It merely measures the amount of T4 thyroid hormone circulating in the bloodstream at the time of the test. It can not tell the vet whether an elevated T4 hormone level is the result of small amounts of excess hormone accumulating in the bloodstream over time as a result of mild hyperthyroidism or whether it accumulated in larger amounts quickly as a result of more severe hyperT. 

Some vets, however, seem to think that a Total T4 test does indicate the severity of the disease (which it does not - it ONLY identifies the current level of circulating T4 thyroid hormone in the blood)), and therefore prescribe a starting dose of methimazole based on that test result. When determining an appropriate starting dose of methimazole, however, it's important to understand that methimazole does nothing to eliminate excess circulating hormone. Methimazole only helps to limit the amount of new hormone released by the thyroid. So all of the excess circulating hormone is either used by or eliminated from the body naturally and gradually after methimazole therapy is started.

Here's the problem. If the starting dose of methimazole is too high and shuts down the thyroid production too far, you won't know it until after the circulating hormone has been naturally utilized or released from the body, and that can take 1-3 weeks after starting the too-high dose. After that 1-3 week time frame is when a "crash" may happen, if it's going to happen at all. If a crash happens, your cat will become hypothyroid and may become extremely ill - nauseous, inappetant, weak. Usually this condition can be reversed by lowering the Methimazole dose, but occasionally the cat simply can not recover and will fail.

Last year, someone posted on this forum about their newly diagnosed hyperT cat. I warned him about the high starting dose of methimazole that his vet had prescribed for his cat, and I begged him to research current dosing recommendations and start at a lower dose and work up to a higher dose, if necessary, to prevent his cat from "crashing". Unfortunately, he chose to comply with his vet's dosing recommendation. A few weeks later, his cat crashed so badly that he had him euthanized. It was such a terribly sad loss, and perhaps a preventable one with much more gradual treatment. I don't want to see that happen to your cat, so I implore you to research your vet's dosing recommendation BEFORE starting your cat on methimazole.

Vets generally recommend a starting dose of 5-10 mg of Methimazole daily (typically split into two daily doses). This is the dosing recommendation they read in their standard veterinary pharmaceutical text. Unfortunately, many people, including myself, have found that even the lower end of this dosing recommendation is too high for our cats and has thrown them into hypothyroidism. Luckily, I was able to bring my cat back to euthyroid (normal thyroid level) by lowering the dose. Others weren't so lucky with their cats.

On the hyperT mailing list, and in some of the more current veterinary research literature, you will find the recommendation to start methimazole at a dose of 1.25 mg twice daily (1.25 mg once daily if the cat has known kidney disease), with retesting in 3 weeks. If euthyroid (normal thyroid level) has not yet been achieved, a small dose increase of 1.25 mg daily is added and the cat is retested in another 3 weeks. This 3 week testing/med adjustment schedule continues until euthyroid is reached.

This "start low and go slow" approach to dosing offers several critical advantages. First, it allows the body to slowly adjust to the decreased thyroid hormone. Second, it helps avoid severe crashes and hypothyroidism from occurring. Third, it protects the kidneys from the potentially devastating effects of a crash. There is NO disadvantage to starting on a low dose of methimazole and working your way up, other than the expense of additional TT4 blood testing at 3 week intervals until your cat reaches euthyroid. It is the safest approach for your cat and one I hope you will discuss with your vet. If your vet tries to insist on starting at a high dose, make sure you understand the potentially dangerous side effects before putting your cat in harm's way. Remember that you are your cat's medical advocate. If your vet's recommendation makes you uncomfortable, say so, and if necessary, find another vet who will work WITH you to safeguard your cat's health.

There are other treatment options for hyperT. Surgery is sometimes offered but is not generally advisable. It is not only a technically difficult and very risky surgery, but it often is not curative because diseased thyroid tissue can sometimes be present outside of the thyroid glands themselves. If this tissue is present, surgery will not remove it, and the cat will remain hyperthyroid.

But there is another treatment option that is very safe and is curative in most cases. It is radioactive iodine (I-131). It involves a single, subQ injection followed by a period of containment until the cat's body eliminates the radioactive material. This is the treatment of choice for people who can afford it, but it is a very expensive option. Still, over the life expectancy of a 10 yr old cat, it would likely be much cheaper to do the I-131 treatment and cure her hyperT permanently than to administer medication every day for the rest of her life, have regular blood testing at least once every six months, and risk the potentially serious side effects of long term methimazole use. Plus, methimazole doesn't cure hyperT. Only I-131 does that.

If, however, you do consider I-131 treatment for your girl, it is essential to run a methimazole trial first to confirm healthy renal function before proceeding with I-131 treatment. Uncontrolled hyperT can mask renal failure by forcing the kidneys to work harder than they would work without the influence of hyperT. The bloodwork of an uncontrolled hyperT patient may indicate renal values within normal range, but there is no way to tell whether those blood values indicate normal renal function or whether the hyperT is forcing diseased kidneys to work hard enough to" look" normal in test results. The true state of the kidneys can not be determined until AFTER the T4 level has been normalized with medication. If and when your cat's T4 level returns to normal range on methimazole AND her renal values (BUN and creatinine) are also in normal range, then she will be a candidate for I-131. If, however, her renal values rise above normal range when her T4 drops to normal, then you are looking at balancing renal insufficiency and hyperT, and the recommendation will likely be to manage her hyperT with medication rather than I-131.

I know this is a lot of information to throw at you all at once, so please post again if you have more questions or need further clarification.

Laurie


----------



## mimitabby (Apr 20, 2010)

wow, Laurie, thank you so much for taking the time to answer my question. The thought of killing Enza's thyroid forever I find very disturbing. However, the treatments you discuss also sound very dangerous and I am SO glad you told me about this.
Enza's liver and kidney function are good and EXCELLENT. I think her major diet being raw food has something to do with that. 
Here's my stupid questions: 
1/ does thyroid ever go back to normal on its own?
2/ how much does I-131 cost and how long do they have to be "contained" (that sounds extremely traumatic)
3/ after they get the I-131, don't they need some OTHER medication since (I presume?) they can no longer make thyroid themselves?
4/ is there another test that might give more useful information before we start messing with this cat with drugs/ and or permanent solutions like the iodine?

We hope she still has a good long life span and I thank you again for your explanation. I will also go check out that yahoo group...

ps Enza is the tortie.. :luv


----------



## laurief (Jun 22, 2008)

mimitabby said:


> wow, Laurie, thank you so much for taking the time to answer my question.


You're welcome. 



> The thought of killing Enza's thyroid forever I find very disturbing.


The great thing about I-131 is that it ONLY kills diseased thyroid tissue. All healthy thyroid tissue is left intact and fully functional. So most cats who undergo I-131 treatment go on to live perfectly healthy lives with perfectly healthy thyroid glands. Occasionally, however, so much of the thyroid tissue is diseased that the remaining healthy thyroid tissue can not support the cat's body properly after I-131 treatment. In that case, the cat will require thyroid supplementation for the rest of her life. This is just a matter of taking a small thyroid pill daily and does not involve the risk of long-term use of a potentially toxic drug like methimazole.



> Enza's liver and kidney function are good and EXCELLENT.


As I explained in my first response, you can not know the condition of your cat's kidneys until AFTER you have normalized her thyroid levels. It doesn't matter that current bloodwork shows her kidney values to be in normal range, because those results can be misleading in a cat with uncontrolled hyperT. Hopefully, Enza's kidneys really are healthy, but you won't be able to confirm that until her kidney values are normal AND her T4 level is normal.



> 1/ does thyroid ever go back to normal on its own?


No.



> 2/ how much does I-131 cost and how long do they have to be "contained" (that sounds extremely traumatic)


From what I understand, I-131 costs somewhere between $1000-1500, depending on the facility and services provided. It is performed only at clinics specially equipped to handle the procedure. Cats must be kept isolated for a specified period according to state law to give their bodies time to eliminate the radioactive material. I believe this time can vary from a few days to a couple of weeks. The clinics that perform this procedure do everything possible to keep the cats as comfortable and happy as possible during the isolation period.



> 3/ after they get the I-131, don't they need some OTHER medication since (I presume?) they can no longer make thyroid themselves?


Ongoing medication is only necessary if there is not enough healthy thyroid tissue left to produce adequate thyroid hormone on its own. In most cases, however, the remaining healthy thyroid tissue can resume normal function, and the cat requires no ongoing medication or other thyroid treatment.



> 4/ is there another test that might give more useful information before we start messing with this cat with drugs/ and or permanent solutions like the iodine?


There may be tests that can be performed to determine the extent of diseased thyroid tissue, but I am not acquainted with such testing. I will refer you to the following website for additional information on thyroid disease, diagnostics, and I-131 treatment:

http://www.radiocat.com

BTW, if my closest I-131 clinic weren't 200+ miles away, and if I could scrounge up the extra cash, I wouldn't hesitate to have my Tommy girl treated with I-131. She's doing well on medication, but I'd much prefer to permanently cure her hyperT with I-131.

Laurie


----------



## mimitabby (Apr 20, 2010)

Well, Laurie, I have contacted both the specialist vet's office and my own today. We have to go back to my own vet this afternoon for a urine analysis. The specialist says that with that info and the senior blood test, they do not have to use medication to discover how the kidneys are working, so I can save time that way, Enza might be radiated as soon as next Monday. 
Meanwhile, we've been feeding Enza more frequently and smaller meals, which seems to be really helping.

Thank you again for your extremely good information and quick help. We want Enza around for another 10 years, she's one of the best cats that I've ever shared a house with!


----------

