Curious about Canine Hypothyroidism? – 10 signs of the misunderstood disease

Hypothyroidism (underactive thyroid) is when the Thyroid glands are not secreting enough of the T4 Hormone which results in a reduced metabolic rate.

Causes of Hypothyroidism

Pinpointing the exact cause of this disease can be tricky however, 90% of dogs diagnosed fit into the following;

  1. Thyroiditis: Where the healthy thyroid tissue is lost due to the dog’s own immune system attacking and destroying it.  Also known as autoimmune thyroiditis and is usually hereditary.
  2. Atrophy: Where normal thyroid tissue is replaced by fat and connective tissue.

Other contributing factors

In the last decade or so fresh feeding dogs has increased considerably and with that comes a lot of mis information about canine nutrition and what dogs need.  So many dog owners are feeding unbalanced or deficient meals to their pets.  Iodine is a trace mineral that packs a powerful punch and is also essential for healthy thyroid function and T4 and T3 production.  Too much of this can create problems and a lack of it can do the same.  Typically, the whole food ingredient used for iodine in home prepared food or commercial fresh food would be kelp.  It is rare that I see a homemade dog food recipe online that contain it or in the right quantities.

T4 contains 4 iodine molecules and T3 contains 3 iodine molecules. When dogs (and people) don’t get enough iodine in their diets the body cannot produce enough thyroid hormones. It is important to note that hereditary Thyroiditis is not impacted by iodine deficiency.  Likewise, it’s important not to over supplement a dog with iodine this can cause over production of T4 and T3 which can then cause the immune system to attack the thyroid gland and reduce levels by up to 25%.

10 Symptoms of Hypothyroidism

It’s important that you know potential signs and symptoms of this disease for when you approach your vet as getting them to test without clinical symptoms can be hard.

Weight gain – with reduced calorie intake

This symptom is probably the most “well known” for dog owners. Due to the slowing of the metabolic rate we can see a huge increase in weight when calories are reduced. However, weight gain alone is sometimes not enough to warrant testing.  Make a food diary, write down calories your dog is consuming or book in a consult with myself to help with weight loss.

If it still isn’t shifting you’re in a better position for getting your dog tested with your vets.

Hair loss/ changes in hair growth and texture

This can be tricky to see in long haired breeds or brindle-coloured dogs. Typically, you will see hair loss on the flanks and base of tail that can be coupled with a bristle like texture and coarse regrowth. Their coat may also appear dull or could look like a puppy’s coat that’s very soft and easily pulled out.  Do not wait for hair loss as this can be progressive sometimes over years.  All because your dog doesn’t have hair loss doesn’t mean there isn’t an issue.

Skin Changes

Skin tends to get a thicker texture and in places where you see hair loss/thinning it can look darker than normal (hyperpigmentation).  Your dog may also exhibit folliculitis, which is risen bumps that burst and scab over, usually on the back and base of the tail. Again these can be difficult to spot in longer haired dogs so it’s important that you inspect your dog’s coat regularly to note any changes

Yeast infections/ear infections

Often missed as a symptom of hypothyroidism as dog owners will go to their vets about the yeast or the ear infections and miss what is the underlying cause. Regardless of treatments the yeast doesn’t fully go aware and flare ups in the ears are common.  Hypothyroid dogs are prone to a leaky gut which in turn can cause yeast to thrive.

Fertility issues and menstrual irregularities

In female dogs some typically symptoms are infertility, still born pups, Pseudo pregnancies (false pregnancies) irregular heat cycles or constant cycles of heat followed by false pregnancies. In males this can result in low libido and sperm count

Behavioural Changes

The Main symptom in my opinion that I see getting looked over is behaviour. Dog’s with strange behaviour patterns such as excessive barking, increased aggression to people or other dogs, standing and staring into space, whining, anxiety, erratic temperament, depression and also hypo attentiveness which can present like separation anxiety.


A typically warning sign of Hypothyroidism, reduced energy on walks, sleeping more than usual (sometimes all day) having to cox them out to eat food.

Joint pain AND OR swelling

Betsy developed a strange gait when she walked almost hopping up a little on her front feet.  Wobbling legs can also be seen in dogs with hypothyroidism as well as joint problems and pain.

Cold intolerance

One of the thyroid glands jobs is to regulate body temperature so if your dog likes to lay on the sofa, or by a fire or radiator or has the reluctance to go outside they may not be regulating.

Breathing problems AND/OR change in bark

It is apparently quite rare but one the symptoms I remember seeing (didn’t link it) was when Betsy struggled to breathe, her whole neck swelled up and subsided after a few days and a trip to the vets.  It wasn’t until I began my hypothyroid research that I realised this was a rare yet early symptom.  Betsy’s bark also changed at her worst and she sounded like she was losing her voice.

Speaking with your vet

Hypothyroidism is a manageable condition so catching it as early as possible to get treatment means your dog can carry on living a normal life. It is important that you go to your vet with a list of symptoms. Creating a symptom diary can really help show your vet the issues you have been experiencing with you dog be it physical or psychological.

DO NOT get side tracked into treating the symptoms. For example, it may be suggested for poor coat condition to be referred to a dermatologist instead to see if this helps. For re occurring ear infections steroid treatments and antibiotics may be suggested.  It is your job to advocate for your pet and whilst I would never ever suggest not to treat secondary infections, we are here to get to the root cause.

What tests to ask for

A FULL THYROID Panel to include the following;

  • T4 (or total T4) – testing this alone is an extremely inaccurate way to diagnose hypothyroidism and will not detect autoantibodies.
  • Free T4 – More accurate test that total t4 and much less likely to be influenced by drugs
  • TSH – As T4 levels fall TSH typically rises
  • T3 and free T3 – usually very high in dogs with autoantibodies
  • TgAA – Elevated in the serum of dogs with autoimmune thyroiditis (the hereditary type)

After the test and understanding the results

It’s important that the results are interpreted correctly and that you also are able to see the levels of each test yourself. When medicating the dosage needs to be right for your dog’s size and also age and metabolisms are different in certain breeds and also between puppies and geriatric dogs.

Giving medication

A few top tips to remember when giving your dog their thyroid medication.

  • Give twice a day – 12 hours apart so your dog has a constant consistent dose in their system.
  • Avoid giving with food as calcium acts to hinder absorption.
  • Give 1 hour before or three hours after food.
  • Avoid foods that contain Soy as these also hinder absorption of the medication.

Always repeat Thyroid panels 4-6 weeks after a change in dosage or when starting medication.


W.Jean Dodds, DVM, Diana R.Laverdure. The Canine Thyroid Epidemic, answers you need for you dog.

Cornell University College of Veterinary medicine

GS Haritha, G Saritha, K Nalini K. Malasseziosis Associated with Hypothyroidism- A Clinical Report in a Dog. Dairy and Vet Sci J. 2017; 2(1): 555581.DOI: 10.19080/JDVS.2017.02.555581

2 thoughts on “Curious about Canine Hypothyroidism? – 10 signs of the misunderstood disease”

  1. Thank you, this is a really helpful summary and one I wish I had, had to hand. I was floundering and reaching out to what for me at the time were the typical and obvious available routes…. mainly the vet and trainers. I was a first time dog guardian, was way out of my depth and whilst my gut told me something wasn’t right – I would never ever have suspected thyroid! My boy was only a little tiny when I first started to question things and 3 and a half when (semi recently) he was diagnosis. As you highlight not all dogs display the most common symptoms, he certainly didn’t (I will be eternally grateful to Junior @healthedog for his practical help, support and advice during this time) My pup does however, have a whole catalogue of things he (and subsequently we) struggle/s with . Both as a direct result of the disease and in my opinion as a consequence of not being diagnosed and medicated sooner. Thus allowing deeper issues to establish, anxiety both his and mine to develop and the good old muscle memory to do its thing!
    You helpfully advise that it is so easy to get distracted – I have frustratedly (and embarrassingly) round pegged, his square holed symptoms to find answers and solutions. My pup mama experience has at times been naive and relied heavily on learning on the job and suck it and see ! I would wholeheartedly echo that you must; do your research! remember you know your dog better than anyone else! press your vet for a full thyroid panel test (they won’t automatically offer this) and in my humble remember that; patience is a virtue!!!! Why? Because if a diagnosis is reached – it is likely to take a bit of trial and effort before the accurate medication dose is balanced. Depending on your dogs journey, they may then need time, understanding and support to heal (including neurologically), which passes ‘the as long as a piece of string test’! Then and if, as in our case behaviour patterns have established there is likely a whole other adventure waiting for you to embrace… For us at least there have been no magic or quick fixes involved – slow and steady is how we roll but now of course with a pup who must surely feel physically better in himself! Testament to this is – he now sleeps ‘our major win’
    Tip from me in addition to the really helpful overview you give is – future retests must take place 4-6 hours after medication has been given.
    Despite now feeling that the vet I have been seeing more recently, does have an understanding of this disease, I have never been advised on dosing twice a day, dosing on an empty stomach as you illustrate or testing as above,! Nor have I been offered any nutritional/feeding advice or guidance (bet that’s no surprise for you). I think I am regularly viewed as a bit of an irritant though :) !!!!
    The only way we will unlock the seemingly mystifying but not uncommon canine thyroid disease is by talking openly about it and more routinely testing . I for one am grateful you have taken the time to share and open a dialogue.
    Much appreciated Deborah

    1. I really hope you’ve found this helpful and I am sorry you went through what you did with your boy! Sally x

Comments are closed.

Shopping Cart
Scroll to Top