Tuesday, February 5, 2013

The Difference Between Hypothyroid & Hyperthyroid Conditions in Pets

Photo: West Zest
Hypothyroidism and hyperthyroidism are both common conditions in dogs and cats. Well, not for both that is. Fresh out of college, another vet tech taught me a great way to tell the difference between the two conditions and it's stuck with me ever since.

Cats are hyper, therefore they become hyperthyroid while dogs most commonly become hypothyroid. I know it's kind of a silly way to remember, but it helped me out as a new technician. So, what is a thyroid anyways?

Thyroid is an endocrine gland found in your pet's body. People have them too, of course. The thyroid gland has some very important jobs like controlling how quickly the body uses energy, makes proteins, and controls the body's sensitivity to hormones.


Hypothyroidism in Dogs


Photo: idea-saras
If a dog is diagnosed with hypothyroidism, it means that their thyroid gland isn't producing enough thyroid hormone. This causes a very slow metabolism usually resulting in excessive weight gain. It can also cause a dog to have an un-thrifty coat that causes poor hair re-growth after a dog has been shaved or clipped. Their skin may also appear dry, thick, and leathery. 

If a dog is going to become hypothyroid, it will usually happen mid-life. Diagnosis of hypothyroidism in dogs is pretty simple and only requires a blood test called a "total T4". If the test shows low thyroid levels, an even more precise test may be run afterwards called a "free T4 by equilibrium dialysis". Or for short you could just say FT4 by ED if you like. 

If the blood test confirms that the dog has a hypo-active thyroid, the next step will be a prescription of thyroid supplements for the dog. This supplement, called levothyroxine, is usually prescribed by a veterinarian to be taken once or twice a day for the rest of the dog's life. Hypothyroidism in dogs is permanent. The supplements usually come as flavored tablets making it easier to medicate you pup. Regular thyroid blood checks and exams will be performed throughout a hypothyroid dog's life to make sure that they are not being over-supplemented. 

So can dogs become hyperthyroid?


The answer is yes - but it's extremely rare. If a dog comes down with hyperthyroidism, the most likely causes are cancer of the thyroid gland or over-supplementation of thyroid hormones. That's why it's important to have your hypothyroid dog's hormone levels checked regularly - to make sure that they are receiving the right dosage of medication. Otherwise, you could be making them hyperthyroid. 

Hyperthyroidism in Cats


Hyperthyroid Cat. Photo: aturkus
As you may have already guessed, hyperthyroidism means that the thyroid gland produces too much thyroid hormones. As mentioned above, this condition affects mostly cats rather than dogs. There are several tell-tale symptoms of hyperthyroidism in cats. Excessively meowing for food, ravenous appetite, and weight loss. Some cats may also have a poor looking coat, experience excessive thirst, and more frequent urination. 

Hyperthyroidism usually affects cats who are older than 10 years. In most cats, diagnosis is easy and requires a simple blood test like the one mentioned for dogs. A very small percentage of cats will show a normal thyroid level for this test even though they are hyperthyroid. This makes it more difficult to diagnose a handful of cats with hyperthyroidism.

What are the treatment options for hyperthyroidism in cats?


There are more options available in the treatment of hyperthyroidism in cats than hypothyroidism in dogs. There is a daily medication called methimazole which is given orally although, this medicine does have its side effects. Side effects of the drug could include vomiting, itchiness, jaundice, loss of appetite, and lethargy. A small percentage of cats will experience these side effects from methimazole. 

Another treatment option is a methimazole ear gel which is applied topically everyday. Many cat owners find this method easier than giving pills to their cat on a daily basis. The ear gel is applied to the skin on the ears and absorbed into the body. Of course, it can cause hair loss on the ears along with the other symptoms of methimazole. Cats who take methimazole will need to have their blood chemistries checked on a regular basis. 

Cat at the vet. Photo: Andrew Ciscel
The best treatment option for hyperthyroidism in cats is radioactive iodine therapy. After a cat has this treatment, they are no longer hyperthyroid. Radioactive iodine is injected under the skin and eliminates the hyperactive tissue in the cat's thyroid gland. No thyroid medication is needed after this treatment. Cats who receive this treatment will have to be kept at the facility for a little while until the radiation levels in their body and waste come down. It's usually not more than 2 weeks however. 

Radioactive iodine therapy may be a little expensive, but the cost is probably well worth it in the end. The cost of medication adds up over time. Plus, it is more convenient than having to pill your cat everyday for the rest of their life. Something both of you will probably be happy to live without. 

Can cats become hypothyroid?


Like dogs, cats can very rarely become hypothyroid. The most likely feline candidates for hypothyroidism are cats who have had a radioactive iodine therapy treatment. Hypothyroidism is not life-threatening, thankfully. If a cat were to become hypothyroid, the treatment would be the same supplement that dogs receive - levothyroxine. 

More Reading


Last month, I read a couple of good posts about thyroid conditions in cats on some other blogs. One was from A Tonk's Tail and talks about the rare condition of hypothyroidism in cats

The other was a series of 3 posts by Mizz Bassie's mom from The Bassie Bulletin. Her cat, Surfeit, was diagnosed with hyperthyroidism and had radioactive iodine therapy treatment. They are a great first-hand account of experiencing hyperthyroidism in cats with a lot of good information. Follow the links to read their story. 

31 comments:

  1. a very informative post Ann. I love reading it and it makes me wonder whether turtles alsi have thyroid problems

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    1. I've worked with a lot of turtles, but have never met one that had a thyroid problem. Good question though!

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  2. We never heard of medication in an ear gel. Wow and it so makes sense. Great information Ann. Have a terrific Tuesday.
    Best wishes Molly

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    1. The ear gel medication was one of the most popular treatment methods among clients. Thanks for reading Molly!

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  3. Woof! Woof! It's interesting that how same human health issues occurs in cats n dogs too. My mom is familiar with this as she suffered from it (its all taken care of). From this, it seems that it is harder for dogs/cats. Golden Thanks for sharing. Lots of Golden Woofs, Sugar

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    1. Glad your mom has it under control now. I think hypothyroidism in dogs is easier to manage than hyperthyroidism in cats.

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  4. Thank you for your interesting post!

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    1. Thanks for stopping by Mr. Easy!

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    2. My Bruno was on levothyroxine for the last few years of his life...and then the doctor put me on it...i'd never shared meds with my dog before :) (NB we each had our own scripts and dosages...didn't mean we actually shared pills)

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    3. Lol, well I knew what you meant! I'm sure you wouldn't want to have a beefy flavored chewable anyways haha!

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  5. That was a wonderful post. I did not know that Hypothyroidism was in dogs. I did have a cat that had the hyperthyroidism and we treated her for 5 years before she had to go to the bridge. She had other problems too and was old. But that was very informative.

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    1. Thanks Marg. It's pretty common for both pets.

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  6. Very interesting to learn, thanks for posting this!

    Oink oink,
    Katie and Coccolino the mini pig

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  7. Well shoot.. I was going to cover that next month. May I link my blog to this article? I'll be talking about a cat who has it and has to have the iodine treatment.

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    1. Lol.. of course Christina! I felt the same way when I read the other articles I mentioned. I've had this one on my to-write-about list forever it seems.

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  8. Very interesting, we were worried about Roxy for a while, because she couldn't seem to lose weight. Then we put her on different food, and she is doing awesome.

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    1. Glad to hear she isn't hypothyroid and is getting her slim lady figure on!

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  9. That was very, very interesting! Thanks so much for putting it together so nicely!

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  10. Ann, I've linked to you and your Share the Love project in today's post...hope you like it

    Your explanation today is clear and concise and I learned something...thanks!

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    1. Aw thanks Gizmo, will be by to check it out!

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  11. Your so good at advising us on so many different topics ( that sounds quite posh for us..BOL )If ever we need to know something, we know where to come. Thank you for taking the time to make it easy reading for us. :) Happy Tuesday xx00xx

    Mollie and Alfie

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    1. Am glad you guys found it easy to read. I try to make things simple to understand.

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  12. My friend is giving thyroid ear gel medicine to her cat. He's feeling much better with it.

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  13. Thanks again for sharing your knowledge. I always confuse the two. My sister's cat has hyperthyroidism and has responded very well to medication.

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  14. Really informative and interesting, Ann. Thanks!

    Our 19 year old cat, Sammy, is hyperthyroid, and has done very well on methimazole for a number of years. :)

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    1. Glad to hear so meowmeowmans. It sure does sound like it if he's 19!

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  15. I have Hypothyroidism! It's interesting what other animals have in common with us. I also find it interesting that cats and dogs have it the opposite way around.

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