Key takeaways:
Hypothyroidism is a common disease in dogs. It’s a condition where the thyroid gland doesn’t make enough thyroid hormone.
Symptoms of hypothyroidism in dogs include fatigue, weight gain, excessive shedding, dull attitude, and the inability to tolerate the cold.
Treatment for hypothyroidism in dogs is oral thyroid hormone replacement therapy, a medication given daily.
If your energetic pup starts showing less interest in exercising as they age, it may not be from simply getting older. It could be hypothyroidism.
You’ve probably heard of hypothyroidism, because it can affect people, too. In fact, some of the symptoms are similar between humans and dogs, like slowing down and gaining weight. But there are differences, too. For example, dogs don’t develop goiters like people do.
For a better understanding of how hypothyroidism may impact your pet, we’ve gathered all the info you need on its symptoms, causes, and treatments.
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What is hypothyroidism in dogs?
Hypothyroidism means the thyroid gland isn’t making enough thyroid hormone to support the body’s functions. When the thyroid doesn’t work properly, it affects the adrenal system, the reproductive system, metabolism, and more. Thyroid hormones also impact nearly every cell in the body.
Hypothyroidism is a common, slow-progressing disease. You may not notice the early signs because they’re often subtle and can be mistaken for other problems.
Signs and symptoms of hypothyroidism in dogs
Hypothyroidism can cause a wide range of symptoms in dogs, including:
Fatigue
Sleeping for long hours
Dull attitude
Lack of interest in exercise
Weight gain without an increase in appetite
Inability to tolerate the cold
Dry hair and skin
Excessive shedding
Loss or thinning of hair
Dark coloring in the skin
Obesity
Slower heart rate
Skin and ear infections
Slow regrowth of fur after clipping
What causes hypothyroidism in dogs?
A couple of different conditions can cause hypothyroidism.
A dog with a thyroid gland that’s been destroyed is said to have primary hypothyroidism, an autoimmune condition.
Either lymphocytic thyroiditis or idiopathic atrophy of the thyroid gland can destroy a dog’s thyroid and cause primary hypothyroidism. Lymphocytic thyroiditis occurs when the immune system attacks the thyroid. Idiopathic atrophy happens when fat tissue replaces thyroid tissue.
Managing heart disease: If your pet’s ticker isn’t working right, don’t worry. There’s plenty you and your veterinarian can do to treat your dog’s heart disease.
Pee problems: Is your pup showing signs of extreme thirst, increased urination, and weight gain? These are symptoms of Cushing’s disease, a serious condition in dogs.
Bath time: Dogs need regular grooming. But how often should you give your pup a bath? It depends on their fur type.
Secondary hypothyroidism is the inability to release thyroid stimulating hormone (TSH). This prevents the thyroid from providing enough hormones to support your dog’s bodily functions.
Primary hypothyroidism is more common than secondary hypothyroidism. But they both cause the same symptoms. Birth defects or tumors can also cause hypothyroidism.
Are some dog breeds more at risk of hypothyroidism?
Hypothyroidism is more common in middle-aged and older dogs. It’s also seen more often in middle-sized and large-sized dogs. And certain breeds are more likely to have hypothyroidism. They include:
Great Danes
Irish setters
Boxers
Doberman pinschers
Dachshunds
Golden retrievers
Dalmatians
Basenjis
Rhodesian ridgebacks
Old English sheepdogs
Maltese dogs
Chesapeake Bay retrievers
Beagles
Cocker spaniels
Shetland sheepdogs
Siberian huskies
Border collies
Huskies
Akitas
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How is hypothyroidism in dogs diagnosed?
Your dog’s veterinarian will perform a physical exam and thyroid blood testing to make a diagnosis. They’ll take any other conditions and medications your dog is taking into consideration.
Diagnostic testing for thyroid hormones can be tricky. That’s because the results don’t always reflect the true health of the thyroid gland.
For example, a dog with hypothyroidism could have a blood test that shows a normal, functioning thyroid. Or a dog can have low thyroid hormone levels on their blood test, but they don’t actually have hypothyroidism. Your vet may need to do more tests to confirm a diagnosis.
Certain medications can also cause low thyroid levels in dogs but not hypothyroidism. These medications include:
Steroids like prednisone
Anti-seizure medications like phenobarbital
Nonsteroidal anti-inflammatory drugs (NSAIDs)
Sulfa class antibiotics
Propranolol
Clomipramine
If thyroid testing is part of your veterinarian’s routine blood tests, they may catch unusual thyroid levels during a regular checkup. Or your vet may notice it if you get your dog’s blood test done for an unrelated issue, such as checking their liver or kidneys.
How is hypothyroidism in dogs treated?
Hypothyroidism is treated with oral thyroid hormone replacement therapy, a specific type of medication given daily. The most commonly prescribed medication is levothyroxine (Thyro-Tabs Canine, Synthroid).
It may take many months to get the correct dosage of medication. Your veterinarian will prescribe a dosage and have you come back in a few weeks to recheck your dog’s blood work. This will tell your vet if the initial dosage is too high, too low, or just right.
If it’s too high or your dog is sensitive to the medication, they could experience symptoms such as:
Having a fast heart rate
Drinking more water
Urinating more often
Losing weight
Showing a change in attitude
Contact your veterinarian if this happens. Once your dog starts treatment, their energy levels could improve quickly. But other symptoms — like hair loss and dark skin coloring — could take more time to improve.
You should continue monitoring your dog’s thyroid levels through blood tests once they start treatment. Your veterinarian will help determine how frequently you should have this done.
What happens if dog hypothyroidism is left untreated?
If left untreated, hypothyroidism can lead to worse symptoms and health complications. Severe hypothyroidism can cause:
Skin infections
Ear problems
Thick skin around the head and face
Heart problems, such as a slow heart rate
Balance issues, such as lack of coordination or a head tilt
High cholesterol
Changes to the surface of a dog’s eyes
Myxedema coma, a rare complication that leads to life-threatening hypothyroidism symptoms
Consult your veterinarian if you notice any of these signs. Myxedema coma can be fatal. Lethargy could develop into listlessness quickly before the coma occurs.
How long do dogs with hypothyroidism live?
Once your dog starts treatment, the general prognosis for hypothyroidism is good. But there isn’t a cure. A dog with the condition will need thyroid hormone medication for the rest of their life.
If your pup’s symptoms don’t improve with treatment, consult your veterinarian. Your dog could have the wrong diagnosis, or they could have another condition, too.
Frequently asked questions
Yes, dogs with hypothyroidism can have seizures. They can also experience other neurological symptoms, such as facial nerve paralysis and vestibular disease (loss of balance).
Cost for initial tests can run from $50 to $150. Yearly follow-up tests can be around $50. Monthly medication costs come out to $20 to $50.
Yes, dogs with hypothyroidism can have seizures. They can also experience other neurological symptoms, such as facial nerve paralysis and vestibular disease (loss of balance).
Cost for initial tests can run from $50 to $150. Yearly follow-up tests can be around $50. Monthly medication costs come out to $20 to $50.
The bottom line
Hypothyroidism happens when your dog’s thyroid doesn’t produce enough hormone. It’s a common disease in dogs. Symptoms can include fatigue, mental dullness, dry skin and hair, and excessive shedding.
Diagnosing the disease can be difficult because some thyroid hormone tests don’t always reflect the health of the thyroid gland. Treatment for hypothyroidism consists of oral thyroid hormone replacement therapy medication. Once treatment is started, symptoms related to energy levels improve quickly, while symptoms involving the skin and coat can take longer to improve.
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References
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Brooks, W. (2024). Hypothyroidism is the most common hormone imbalance of dogs. Veterinary Partner.
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Daniel, R. (n.d.). Neurologic manifestations of hypothyroidism. MSPCA Angell.
González Sanz, S., et al. (2017). Prevalence of neurological signs in hypothyroid dogs at diagnosis. Veterinary Information Network.
Heseltine, J. (2024). Hypothyroidism in animals. Merck Veterinary Manual.
Nelson, R. W. (2013). How I treat: Canine hypothyroidism. Veterinary Information Network.
Royal Veterinary College University of London. (2022). New research highlights dog breeds at most risk of hypothyroidism.
Schoeman, J. P. (2011). Canine hypothyroidism. Veterinary Information Network.
The VIN Dermatology Consultants. (2018). Hypothyroidism in dogs. Veterinary Partner.
U.S. Food and Drug Administration. (2021). Hypothyroidism in dogs — there are FDA-approved drugs to treat it.
Walther, R. (n.d.). Hypothyroidism in dogs: causes, symptoms, treatments. Pawlicy Advisor.
