Hypothyroidism in dogs

Hypothyroidism in dogs happens when their body produces too little thyroid hormone. It affects around 1 in 400 of the population. Neutered, middle-aged dogs and certain breeds are most likely to get hypothyroidism.

Hypothyroidism is the most common hormonal disease in UK dogs. There’s no cure, but the condition can be readily managed with medicine from your vet. Hypothyroidism isn’t easy to recognise in the early stages, because symptoms can be vague and common to other illnesses. But the sooner it’s identified and treated, the quicker your dog can return to a full and active life.



What is hypothyroidism in dogs?

Hypothyroidism means there’s too little of the thyroid hormone, thyroxine, in your dog’s system. Thyroxine is produced by the two small thyroid glands in your dog’s neck. It controls the metabolic rate, or how quickly the body burns up energy.

Why does it happen?

95% of the time hypothyroidism in dogs happens either because:

  • The body’s own defence system mistakenly attacks and destroys the thyroid gland.
  • The thyroid gland withers away for no known reason. Vets call this idiopathic atrophy.

The thyroid hormone has profound effects on your dog’s metabolism. Think of metabolism as a car’s acceleration. Hypothyroidism means no matter how hard you press the accelerator pedal, the car is underpowered and slow. For your dog, this means that many body systems that depend on thyroid control stop working properly.

Inside your dog’s body this ‘slowing down’ affects important body systems and processes, including:

  • Heart
  • Brain and nervous system
  • Skin
  • Control of body temperature and bodyweight
  • Energy levels
  • Fighting infections

Early diagnosis of hypothyroidism is challenging because the disease mimics so many other illnesses which also affect one or more of these body systems.



Symptoms of hypothyroidism in dogs

Symptoms of hypothyroidism result from reduced energy for body functions.

Common symptoms include:

  • Low energy levels and sleeping more
  • Being less alert
  • Gaining weight without eating any more
  • Having dry scaly, flakey skin
  • Symmetrical (matching) hair loss from both sides of the body
  • Skin infections
  • Less energy and enthusiasm for walks
  • Searching out warm places to lie


hypothyroidism in dogs
Lethargy is a common symptom



What are the risks of hypothyroidism?

Age and breed have the biggest impact on your dog’s risk of developing hypothyroidism.

Risk factors include:

  • Increasing age.
  • Belonging to certain breeds: Doberman Pinschers, Boxers, Shetland Sheepdogs, American Cocker Spaniels, Irish Red Setters, Rhodesian Ridgebacks, Golden Retrievers, and Alaskan Malamutes.
  • Being neutered.

Complications of hypothyroidism

As well as mimicking other illnesses, low thyroid levels can also worsen them, affect the response to treatment, or increase your dog’s susceptibility. This includes:

Are my other pets at risk of hypothyroidism?

Hypothyroidism affects individual dogs. Your family and other pets are not at risk of ‘catching’ hypothyroidism.

However, medicines that suppress your dog’s thyroid hormone levels can have the same effect on humans:

  • Medicine for hypothyroidism should be handled carefully
  • Wash your hands after handling tablets
  • Clean surfaces thoroughly after contact
  • Keep all medicines out of sight and reach of children and pets



How do vets diagnose hypothyroidism in dogs?

Hypothyroidism in dogs is often missed in the early stages. This is because the wide range of symptoms can be vague and common to multiple other illnesses.

Vets diagnose hypothyroidism based on the following:

  • The history: any changes you report, like gaining weight, skin changes, or low energy.
  • Physical examination: symmetrical hair loss, scurfy skin, slow heart rate.
  • Blood tests: general check and thyroid hormone level.


blood tests dogs
Blood tests are part of the diagnosis


Diagnosing hypothyroidism isn’t straightforward. Your dog will need more than one blood test before your vet can confirm if they have hypothyroidism. This is because low thyroid levels in the blood can be caused by other factors, including

  • Certain medications: including steroids and some antibiotics.
  • Other illnesses: dogs who are unwell for other reasons often have lower than normal thyroid levels. The sicker the patient, the lower their thyroid levels. Vets call this ‘euthyroid sick syndrome’.

Your vet won’t want to diagnose hypothyroidism if there could be another explanation for low blood thyroid levels that doesn’t need lifelong treatment.


Vet treatment

How do vets treat hypothyroidism in dogs?

Hypothyroidism can’t be cured. Controlling the symptoms means replacing the missing thyroid hormone with a man-made alternative.

Your dog’s hypothyroidism treatment includes:

  • Having daily medicine by mouth (tablets).
  • Attending regular vet checks to make sure they are getting the right dose of their medicine and aren’t getting any side effects.
  • Having regular blood tests to check thyroid levels: once or twice per year or after changes in medicine dose.

Symptoms will improve within a very short time and even hair regrowth is likely within 6 months of starting the right treatment. With the correct treatment, dogs with hypothyroidism should return to a full and active life.


Home treatment

Caring for your hypothyroid dog at home

There are no home remedies for hypothyroidism in dogs. Your dog with hypothyroidism needs medicine from a vet.

But home support is essential to ensure your dog gets the most benefit from their treatment:

  • Give thyroid and other medicine as prescribed at the correct dose and time.
  • Make sure your dog takes their medication.
  • Ask for help or alternatives if you are struggling to give tablets.


Can hypothyroidism in dogs be prevented?

Hypothyroidism in dogs can’t be prevented. But early diagnosis and treatment is the best way to return your dog to their old selves sooner.


When to worry

When to worry about hypothyroidism in dogs

Hypothyroidism can be associated with other, apparently unrelated illnesses.

Call a vet if your dog is:

  • Sleepy and unwilling to move.
  • Gaining or losing weight unexpectedly.
  • Having seizures or collapsing.
  • Hard to rouse or cold to touch.

Joii can help with:

  • Recognising the symptoms of hypothyroidism.
  • Advice on testing for hypothyroidism.
  • Suitable diets for dogs with weight gain.
  • Tips for giving your dog tablets and other medicines.
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