Hypothyroid Dogs

Is Your Dog Overweight and Lazy with Thinning Hair?
Your Dog May Need a Thyroid Screening.


The thyroid glands located in the neck produce 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. Hypothyroidism in dogs is usually caused by inflammation or shrinkage of the thyroid gland. Thyroid cancer can cause hypothyroidism although it does not occur commonly in dogs.

Hypothyroidism occurs in any breed or sex but it is more commonly found in medium to large breed dogs and usually in middle aged dogs. The breeds most susceptible to hypothyroidism include:

  1. Golden Retrievers
  2. Labrador Retrievers
  3. Dachshunds
  4. Boxers
  5. Cocker Spaniels
  6. Greyhounds
  7. English Bulldogs
  8. Great Danes
  9. Doberman Pinschers


Hypothyroid dogs gain weight


A hairless "Rat Tail" is very suggestive of hypothyroid dogs


A "Tragic Expression" on the face of a Golden
retriever with hypothyroidism.


Non-itchy hair loss over the trunk and rump on
both sides suggests hypothyroidism.

Symptoms of Hypothyroidism

  • Skin abnormalities, such as dark patches or dry skin
  • Hair loss or poor hair coat
  • Lethargy, excess sleep
  • Weight gain
  • Chills, poor cold tolerance
  • Slow heart rate
  • Constipation
  • Infertility

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 and reduced ability to tolerate the cold. The 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 (axilla).

Hypothyroid dogs often have ear infections and show ear pain, redness, and odor.

Hypothyroid dogs may also develop skin infections which may be itchy and result in sores on the body. A frequent sign of hypothyroidism is recurrent superficial skin infection, usually with Staph bacteria.

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 with hypothyroidism include dilation of the esophagus (megaesophagus) causing regurgitation, and abnormal function of nerves or muscles leading to weakness or abnormal ability to walk. Some unspayed female dogs will not have heat cycles. Hypothyroidism can also be an infrequent cause of epileptic seizures.

Routine blood tests can be affected by hypothyroidism, although the changes are not consistent and can be subtle. Dogs may have a mild anemia and increased levels of cholesterol.


At Animal Hospital of Montgomery, we can do routine thyroid screening, cholesterol levels, and
anemia testing in our lab in just a few minutes.

Make an appointment for Thyroid Blood Testing

Hypothyroid dog before and after treatment with hormone



Thyroid replacement hormone comes in tablet forms in many
different tablet strengths.


Leventa is a liquid thyroid
replacement that is dosed according
to the weight of the dog.

The treatment for hypothyroid dogs involves providing hormone replacement therapy in order to get the thyroid hormone level in the blood back to a normal range. This treatment is provided for the remainder of the dog's life. An initial twice a day dose of the thyroid hormone is prescribed using either tablets or liquid. After one month of hormone replacement, the dog is rechecked to monitor differences in weight and hair coat . At that visit the thyroid level is measured 4-6 hours after the morning dose. Adjustments in hormone replacement can be made until the blood level is regulated. Once the thyroid level in the blood is in the normal range, that is usually the dose that will always be given.

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