Canine Hypothyroidism

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The thyroid gland is a bilobular organ next to the trachea on the underside of the neck.  Each lobe is the shape, consistency, color and size (in a medium-sized dog) of a Swedish Fish, which from here on should be included on the candy’s packaging, because how cool is that??

The thyroid gland produces hormones that control the speed of the body’s metabolism.  As important as it is, you would never notice it was there unless it started underproducing or overproducing thyroid hormones.  Everyone (with bones) has one.

In canine hypothyroidism, the immune system destroys part of the thyroid gland, and it is unable to produce as much thyroid hormone as the body needs and the metabolism slows down.  The most common sign of an underactive thyroid gland is unexplained weight gain.  Low thyroid levels also may cause poor hair coat and skin health, the inability to stay warm, fatigue and even depression.

Dogs Prone to Hypothyroidism

Hypothyroidism is typically diagnosed in middle aged dogs.  Larger dogs develop the disease more often than smaller dogs.  Any breed or mix can develop the disease, but it is more common in some breeds than others.  The ten breeds most commonly diagnosed with hypothyroidism can be found on the Vet Info website.  An extensive list of breeds prone to hypothyroidism can be found in an excellent active registry by Michigan State University.

Cats and Dogs

Dogs with thyroid issues (almost) always have underactive thyroid glands which cause lower than normal metabolism and the disease called hypothyroidism.  Cats with thyroid issues (almost) always have overactive thyroid glands which cause higher than normal metabolism and the disease called hyperthyroidism.

And Now Back to Dogs…

Canine hypothyroidism is usually straight forward to diagnose and treat.  If the disease is suspected, thyroid hormone levels are measured with a simple blood test.

The kicker is that any illness can cause decreased thyroid levels without primary thyroid disease actually being present.

Sick euthyroid – having low thyroid levels caused by an illness other than hypothyroidism

When dogs are ill, we try to address all other issues and bring them back optimal of health before searching for a hypothyroidism diagnosis.  This may be a problem if the primary issue could be hypothyroidism OR something else.  If we test for low thyroid levels and find them, do we keep looking or have we found the primary problem?  As with so many other things in medicine, “it depends.”

Another potential snag is that some hypothyroid dogs do not show low thyroid hormone levels on blood tests.    Most do though.  If thyroid hormone levels are normal on initial screening tests but hypothyroidism is still suspected, more exhaustive testing can be done.


Treatment for hypothyroidism is an synthetic thyroid hormone replacement medication called levothyroxine.  The dose is determined based on the dog’s size, and the medication is given orally twice a day for life.  Thyroid testing is usually done every several weeks until thyroid levels and clinical signs are stable, and then thyroid levels are tested every six to twelve months.  Prognosis for a hypothyroid dog on medication is great.

What Has Been Your Experience With Canine Hypothyroidism?

Hypothyroidism is fairly common in dogs.  I have diagnosed and treated many patients, but never had a dog of my own with the disease.  If you have, can you share your wisdom here, especially for other pet lovers starting on the hypothyroidism journey with their own dog?  Was diagnosis straight forward?  What signs tipped you off that something was wrong?  Has regulation been easy or hard?  Is twice daily medication an issue?  What else should other dog lovers know about the disease?

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May your healthy pets stay healthy, and may your hypothyroid pets be as healthy as healthy pets!

17 thoughts on “Canine Hypothyroidism”

  1. One of my dogs, Roscoe, has it and takes soloximine (sp). His mate, Angie the Airedale, is wild and keeps him moving. Roscoe was abused and very shy so we have one terrfied and one terrorist. Love both.

  2. We’ve had several greyhounds (some were fosters) with hypothyroid issues and they were almost all discovered by way of lab work done in conjunction with behavioral changes leaning towards aggression.
    Apparently greyhounds often present with a lower than “normal” T4 level when they are, in fact, healthy. If your pet shows signs of hypothyroidism, don’t hesitate to have a full thyroid panel done and not just depend on a single T4 value as a means of diagnosis.

  3. My dog had a blood test and the Vet said she had hypothyroidism at age 4. She is on the thyroid medication mentioned in your article above. No problem with weight gain as she eats real meat, raw and cooked, and fresh or frozen real veggies and fruit with cooked cooled sweet potato slices for fiber, also banana and apple slices. No issue with energy. She is highly energetic Golden Retriever and doesn’t slow down at 9 years old with 2 hours of daily running, swimming, fetching, digging and fishing in the summer and the cooler months walking and jogging on the local park trails.

    Biggest concern is she became quite aggressive towards other dogs at this time she was diagnosed with hypothyroidism. She has always been very dominate towards other dogs as soon as she was 1 years old and always had a high tail since a puppy and needs a strong pack leader to keep her in line or she will outsmart anyone who doesn’t know much about dogs.

    Don’t know if the aggressiveness towards dogs was caused by the imbalance of the thyroid. I read that some dogs feel imbalanced so they can be more aggressive with other dogs. She loves children and all people.

    My question is the synthetic thyroid medication. I would like to put her on a BioIdentical thyroid medication as I think she would be more balanced then on this synthetic thyroid medication. Are Holistic Veterinarians prescribing a BioIdentical Thyroid Medication for Hypothryroidism in dogs? I know they have a BioIdentical Thyroid Medication for Humans with hypothyroidism, but is there one available for dogs yet?

    I just read that Coconut Oil is great help for hypothyroidism in both humans and dogs. So I will supplement with that starting next week.

    Trying to find a BioIdentical Thyroid Medication for dogs?

  4. RE: Hypothyroidism
    Labrador (happens to be a Working Service Dog), was always “up for anything”! Since he’s with me 24/7, spending our days on a working Horse Farm was no big deal… until last year. He turned 7 years old and almost “over night” went from a Bright-Eyed, Enthusiastic, Exceptionally ‘Fit” animal to a lethargic, chubby, I-wanna-stay-on-the-couch dog with SUCH A PATHETIC LOOK to his face. To the Vet we go. One simple explanation to the Doc, one (maybe 2) simple tests… Hypothyroidism. Initial dosing was too much for the dog (he “stressed) so we had to cut it in half and slowly build to his maintenance dosage. Twice daily dosing was recommended by my vet to keep the levels constant. Dosing issue??? Absolutely none… since he’s fed at 12 hour intervals, the tiny little pill is simply dropped into his kibble. The only lingering issue I see is that this once ROBUST boy is still cold-intolerant. SO? Big boy now wears a sweater or coat if we’re going to spend much time outdoors. We no longer spend our days on the farm, but he’s still very eager to play, swim, walk in the park….. I got my Paddy back!!!! (if only the Addison’s in the Rott/Shep had been that easy and “inexpensive” to deal with……..)

    • I have had a very similar experience with my border collie, Fiona. She is also my SD and goes EVERYWHERE with me. Usually she is SO excited to leave the house ready for whatever adventure the day presents. A month and a half or so ago she started to get really lethargic, giving me these pathetic looks when I pulled her vest out (like she was saying “Really? You want me to get up right now?”), being REALLY snippy and posessive with our roommates dog, losing hair on her tail and getting a dull wirey coat, gaining weight (2lbs in 2 days I measured recently), and not really playing at all like the crazy dog she used to be (the breeder told me that she was hyper for a BC and was going to be a terror). We went to the vet yesterday because I suspected hypothyroid and sure enough, I got a call today saying that her levels were significantly low. The only sticking point is that she is only a year and a half. Usually (in BCs at least) hypo doesnt present until young middle age at the earliest (like 3 or 4). Of course, as with anything medical, no one creature presents exactly the same as the others everytime so anything is possible really. Because the vet was seriously surprised that her levels were so low so we’re going to start a trial run of replacement hormones in lieu of the $113 free t4 blood test. So, hopefully I’ll be getting my gal pal back soon!

      Just remember guys, if you think something is wrong with your dog, don’t ever let a vet blow you off. It’s their job to make sure you and your dog are comfortable and you will always know your dog better than your vet. If you ask for a test to be run, there should be no reason the vet would deny you unless of course it would put your pet under undue stress. If you have a vet that does this, find a vet who doesn’t. I am very lucky to have an amazing vet and as soon as I mentioned that I would like to have Fiona tested, she immediately said ok and called in the tech. Stand your ground and take care of your pets! They can’t speak for themselves so you have to 🙂

  5. My 8 year old female doberman has had hypothyroidism for a few years and has been taking 0.8mg soloxine twice daily. The dosage was fine for quite some time, but recently she started having behavioral issues that our vet attributed to too high of a dose. She would get very restless, skittish, and needy. We cut back her dose of soloxine and she got better, but then she started exhibiting signs of low thyroid again so we slowly increased the dose and soon found her back at the old dose. We’ve been dealing with this yo yo effect for the last 6 months or so (0.6mg is too little, and 0.8mg is too much). Is there a bioequivilent thyroid hormone that would be appropriate for dogs or any other alternative to the synthetic hormone? Any help would be greatly appreciated.

  6. Stanley, who is an 11 year old pit bull, also was recently diagnosed with hypothyroidsim. The diagnosis came about when the vet had removed a tumor on Stanley’s side approximately six months prior. According to normal “hair growth ” standards, Stanley did not meet those requirements, hence further testing. He then was put on a Twice a day routine of Thyro-Tab. This medication was Only given for about two weeks and abruptly taken off. The Thyro-Tab extremely hindered any of his continence. A fully house trained dog was having several accidents a day. This medicine took about two weeks to leave his system. He has yet to have further testing and tweaking of medications. Slowly his body is deteriorating and his attitude is undesirable, we are a work in progress. Any suggestions and/or ideas on diet, exercise, etc. Would be greatly appreciated.


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