Canine Hypothyroidism

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hypothyroid dog
Symptoms of canine hypothyroidism
Diagnosis of canine hypothyroidism
Treatment of canine hypothryoidism

Canine Hypothyroidism is a relatively common disease. It most commonly affects middle aged to older dogs. The breeds most commonly affected are the Golden Retriever, Doberman, Great Dane, Daschund, Boxer and Sheltie. This is a treatable condition but is almost always a condition that requires lifelong medication.

hypothyroid dog

A dog with hypothyroidism usually has one or more of the following symptoms:

  • weight gain
  • difficulty losing weight
  • lethargy
  • poor hair coat (often very coarse/rough feeling)
  • hair loss over the tail (rat tail appearance) or on either side of the body
  • repeated skin or ear infections

Hypothyroidism is usually diagnosed by a blood test. Most dogs with this condition will have a low T4 level. However, sometimes we can see a low T4 because of other conditions such as a concurrent skin infection or other illness. Therefore, the best way to diagnose hypothyroidism is to do a thyroid panel. This looks at the T4 and several other factors including T3, TSH and more. Many labs will now do either a "T4 by equilibrium dialysis" or a "2-step T4" which are accurate tests for hypothyroidism. However, these tests are more expensive than just a regular T4 level.


Dogs with hypothyroidism usually need to be placed on a thyroid supplement for the rest of their lives. This medication is called levothyroxine. It comes in a pill form. Your vet will determine what dose is the best to give depending on how your dog's thyroid profile looks.

A few weeks after starting medication, your vet will repeat one or more of the thyroid tests to make sure you are giving the right amount of medication. Once the level has been stabilized most vets will recommend a test every 6-12 months.

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Dr. MarieDr. Marie is a veterinarian who practices in a busy animal hospital in Ottawa, Ontario. She created Ask A Vet Question as a resource for good, accurate veterinary advice online. Dr. Marie treats dogs, cats, hamsters, guinea pigs, and rats. She has been a vet since 1999.

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