Thyroid Hormone Deficiency in Dogs

The thyroid gland in dogs functions like the thyroid gland in people.  It releases hormones, especially T3 and T4, that control metabolism.  Without T3 and T4, humans and dogs would die.  Sometimes, the thyroid gland stops producing enough of these hormones, causing the dog to get sick.  If the thyroid glands produce too low an amount of these hormones, the dog will die.

Hypothyroidism, the technical term for low thyroid hormones, is most prevalent in middle aged dogs who are medium to large.  Neutered and spayed dogs are more at risk than intact dogs.  Hypothyroidism seems to be hereditary in some breeds.  The following breeds are most at risk of developing it:

Hypothyroidism can cause a lengthy list of symptoms.  They are: lethargy, generalized weakness, inactivity, mental dullness, unexplained weight gain, hair loss, excessive hair shedding, poor hair growth, dry or lusterless haircoat, excessive scaling in the skin, recurring skin infections, intolerance to cold, and rarely, tilting of the head to one side, seizures, and infertility.  Since many of these symptoms can be mistaken for laziness, it may take a while to realize the dog is ill.

The causes of hypothyroidism are largely unknown.  As mentioned, it runs in some breeds.  It can be the result of a congenital disease, an iodine deficiency, cancer of the thyroid gland, or an after effect of some medical treatment, including surgery to remove a cancerous thyroid gland.

When you take your dog to the veterinarian showing symptoms of hypothyroidism, he will run routine blood and urinalysis tests.  He will also run a panel containing tests for the level of T3 and T4 to see if the thyroid is functioning correctly.  Finally, radiographic studies may be done to see if there is a tumor on the thyroid gland or some other abnormality that is causing the low thyroid hormone problem.

Thyroid disease requires life-long treatment.  If there is a tumor on the thyroid gland, it may need to be removed.  This surgery is not too difficult and usually has a good outcome.  After surgery, or in lieu of surgery, dogs are given synthetic thyroid hormones in specific quantities depending on their weight and health.  It may take several rounds of dosage adjustment and blood tests to check thyroid levels to reach the dog’s optimum level of T3 and T4.  However, once you do reach that level, the dog should get better rather quickly.  As the dog loses weight, the dosage of the medicine may need to be adjusted.  Never adjust it yourself.  Always take the dog to the veterinarian and let them adjust it based on the blood level of the hormone.  Never, ever, stop giving the dog the thyroid hormone, especially if the dog’s thyroid has been removed.  This can kill your dog.

The thyroid pills are small and can easily be hidden in treats or other food to give to the dog.  Most dogs adjust to this routine quickly and take their medicine without complaint.