Hypothyroidism in Dogs

If your dog seems sluggish, has gained weight, and doesn’t seem interested in being active, he or she may have an underactive thyroid.

The thyroid gland (located near the larynx) is an important gland in both people and dogs. It releases a number of hormones, including T3 (liothyronine) and T4 (levothyroxine). These hormones control the regulation of metabolism. Hypothyroidism is a disease where the dog’s thyroid gland is underactive and therefore not producing enough T3 and T4 hormones. This can lead your pup to having intolerance to cold, along with hair loss and changes in skin.

The most common cause of hypothyroidism in dogs is autoimmune thyroiditis, where the dog’s own immune system attacking the thyroid gland tissue. In addition, there are two types of autoimmune thyroiditis, known as lymphocytic thyroiditis and idiopathic thyroid atrophy. Both of these types result in the failure to produce enough thyroxine, and treatment is the same for both types. Genetics plays an important role in autoimmune thyroiditis, which is why dogs with this type of hypothyroidism should not be bred.

Hypothyroidism typically affects dogs in their middle age and it is also more common in larger breeds. While the disease occurs equally in both males and females, spayed females are more likely to have hypothyroidism than intact females. It should be noted that intact females might be more susceptible to fertility issues, although this may be best if the disease is genetic. Additionally, certain breeds are more susceptible to the disease.

Breeds that are more likely to have hypothyroidism are:

  • Golden Retriever
  • Doberman Pinscher
  • Irish Setter
  • Miniature Schnauzer
  • Dachshund
  • Shetland Sheepdog
  • Cocker Spaniel
  • Others

Causes: It can be difficult to discern why exactly the thyroid gland does not produce enough hormones. One possible reason already mentioned is the dog’s immune system begins killing the cells of the thyroid gland. Cancer in dogs may also cause the thyroid to begin shutting down. In rare cases, congenital hypothyroidism may be diagnosed.

Diagnosis: To be diagnosed with hypothyroidism, your dog will need to see a veterinarian, who will then determine which blood tests to administer based on his symptoms. Hypothyroidism is often over diagnosed due to its common symptoms such as weight gain or lethargy, both of which are present in other diseases. To be sure of your dog’s diagnosis, your vet will need thorough information from you including your pet’s background and any past medical issues.

Possible tests your vet could administer include:

  • Baseline T4 Test
  • Free T4 by Equilibrium Dialysis
  • TSH Level
  • TSH Response Test

Treatment: Dogs that are diagnosed with hypothyroidism can usually be treated with a synthetic thyroid medication such as Soloxine or Thyroxine. Although the symptoms of hypothyroidism should disappear with medication in a few months, the dog will need to be on this medication for its entire life with routine blood tests to make sure the dosage is correct.

If you are worried your dog may have an underactive thyroid, please see your veterinarian immediately so your dog can return to his normal healthy state.



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