Hypothyroidism in Dogs 

What is Hypothyroidism?

All animals need thyroid hormone for their body to work normally.

The thyroid hormone is called thyroxine.

Thyroxine controls how well the body turns food into fuel.

Hypothyroidism occurs when the thyroid gland isn't active enough, meaning that the body does not have enough thyroxine. 

The result of this low level, or lack of thyroxine, is that many organs in the body, including the skin, don't work as they should do. This leads to a wide range of symptoms, and makes hypothyroidism tricky to diagnose. 


It is a very common disease, affecting all breeds and most commonly in dogs who are in middle age.


  • Lethargy

  • Weight Gain

  • Dullness

  • Drooping Eyes

  • 'Tragic Facial Expression'

  • Skin Pigment Changes

  • Coat Changes - Hair Loss 

  • 'Rat Tail'

  • White areas appearing on the surface of the eyes

  • Nervous System Signs

  • Infertility


If hypothyroidism is suspected, then we would check hormone levels via blood tests.


Sometimes, thyroid treatment is started as part of the diagnosis. This is because other diseases can mimic thyroid problems.



Hypothyroidism treatment is usually via tablets. 

Once on treatment, your dog will need blood test monitoring to make sure treatment is working.

What about Cats?

Hypothyroidism does occur in cats, but it is very rare.

Cats usually have the opposite problem, in that their thyroid gland produces too much thyroid hormone. 

See hyperthyroidism in cats for more information.