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Hypothyroidism

Randy Walker DVM

About Hypothyroidism...

Hypothyroidism is a condition in which the patient has a deficiency of thyroid hormone in the bloodstream. As a primary condition, hypothyroidism occurs almost exclusively in dogs.

How Is Thyroid Hormone Produced And What Does It Do In The Body?

Thyroid hormone is produced by the thyroid glands which are two small glands located in the neck near the larynx (voice box). In the healthy dog, thyroid hormone is secreted into the bloodstream in steady amounts and (simply put) it regulates the patient's metabolism. A deficiency of thyroid hormone (called hypothyroidism) can lead to a slow metabolism while an over abundance of thyroid hormone (called hyperthyroidism) can lead to an overactive metabolism.

Are The Symptoms Of Hypothyroidism In The Dog?

The symptoms of hypothyroidism can range from mild to severe and will vary from patient to patient. The "classic" symptoms of hypothyroidism are lethargy (just wants to lay around), excessive sleeping, seeking warmth, mental dullness, weight gain, dry coat and skin, excessive shedding, hair thinning over the body, and a "tragic expression" due to puffiness around the face. Dogs with hypothyroidism will often show one or more of the above signs. Rarely are all of these signs noted in the same individual.

Do Cats Get Hypothyroidism?

Primary hypothyroidism (that hypothyroidism that is not secondary to some other disease) is rare in cats.

Which Dogs Are More Likely To Get Hypothyroidism?

Hypothyroidism is most common in medium to large breed dogs usually over 2 years of age. Hypothyroidism can be inherited so dogs who's parents were hypothyroid will themselves be more inclined to be hypothyroid.

What Causes Hypothyroidism?

About half the cases of hypothyroidism are due to the thyroid gland being attacked by the dog's own immune system. Although there are several theories, no one knows for sure why this occurs. In most of the rest of the cases of hypothyroidism the exact cause of the hypothyroidism is unknown. As stated above, the tendency to become hypothyroid can be inherited.

How Is Hypothyroidism Diagnosed?

Hypothyroidism is diagnosed through a blood test.

How Is Hypothyroidism Treated?

We give a daily (or twice daily) thyroid supplement to the hypothyroid patient.

Briefly, Describe The Treatment Protocol For The Hypothyroid Patient.

After the initial blood work establishes a deficiency in thyroid hormone, the patient is placed on a trial dose of thyroid hormone supplement. Blood tests are used periodically to arrive at the proper maintenance dose for this particular patient. Afterward the patient is continued on thyroid supplement once or twice daily and the thyroid level is routinely checked once every 6 months.

Why Should The Thyroid Level Be Checked Once Every 6 Months?

The thyroid level should be checked every 6 months because the amount of thyroid hormone produced by the body (and therefore the amount of supplement needed) will vary with time, season, and individual. patient factors such as other diseases, exercise, age, etc. It is not uncommon for the requirement for thyroid supplement to go up or down and we periodically need to change the thyroid hormone dosage to avoid either over-supplementing or under-supplementing the patient. 


- Randy Walker DVM
Sun Lakes Animal Clinic
May 16,2004



"Until one has loved an animal, a part of one's soul remains unawakened."
- Anatole France, 1921 Nobel Prize Speech -


Titlebar Image: The Gentle Doctor, 1937-38 by Christian Peterson (U84.179) - Iowa State University