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Veterinary Teaching Hospital

Hypothyroidism in dogs

What is hypothyroidism?

Hypothyroidism in dogs is usually caused by inflammation or shrinkage of the thyroid gland, which is located in the neck and produces hormones that affect the function of many parts of the body. Dogs with thyroid disease usually have a low production of thyroid hormones.

Overactive thyroid glands in the dog are rare and are usually associated with cancer. Thyroid cancer can cause hypothyroidism, although it does not occur commonly in dogs.

Hypothyroidism occurs more commonly in medium to large breed dogs and usually in middle-aged dogs. Breeds commonly affected include golden retrievers, Doberman pinchers, and Irish setters.

Closeup of a retriever.
dog, retriever

What are some of the symptoms of hypothyroidism?

The most common signs of low thyroid function in dogs include:

  • loss or thinning of the fur
  • dull hair coat
  • excess shedding or scaling
  • weight gain
  • reduced activity
  • reduced ability to tolerate the cold

Hair loss occurs primarily over the body, sparing the head and legs, and is usually not accompanied by itching or redness of the skin. Some dogs will have thickening of the skin and increased skin pigment, especially in areas of friction, such as the armpit. Hypothyroid dogs often have ear infections and show ear pain, redness, and odor. Hypothyroid dogs may also develop skin infections that may be itchy and result in sores on the body. The accumulation of substances called mucopolysaccharides can cause the muscles of the face to droop, giving the dog a facial expression that is sometimes called “tragic.”

Less commonly recognized signs that may be seen in a small number of dogs include dilation of the esophagus (megaesophagus) causing regurgitation and abnormal function of nerves or muscles leading to weakness or abnormal ability to walk.

How is hypothyroidism diagnosed?

Blood tests can confirm a suspected diagnosis of hypothyroidism. Blood testing for hypothyroidism is often performed as a panel of several tests. The results of some of these tests can be influenced by the presence of other non-thyroid diseases, so test results must be considered in light of the whole picture.

How is hypothyroidism treated?

Treating hypothyroidism requires giving an oral replacement hormone for the rest of the dog’s life. Initially, thyroid hormone is usually given twice daily. Once the hair coat begins to improve, some dogs can be maintained on once-daily medication. It usually takes 4 to 6 weeks before regrowth of the fur is apparent.

Where can I get help if my dog has hypothyroidism?

Our board-certified veterinarians and specialists can help you get an accurate diagnosis and develop a treatment plan. Call 509-335-0711 to schedule an appointment or for more information.


This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian. Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.