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Hypothyroidism Can Slow Down Older Dogs

Pet Column for the week of August 12, 1996

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
By Joseph Hahn
Information Specialist

All mammals have a thyroid gland. It is located in the neck and constantly produces thyroid
hormone which speeds up metabolism. Hypothyroidism occurs when the gland stops
functioning and producing thyroid hormone. It is one of the most common hormonal

"Hypothyroidism usually happens for unknown reasons," says Dr. Leslie Henshaw, a
dermatology resident and veterinarian formerly at the University of Illinois College of Veterinary
Medicine Teaching Hospital at Urbana. "Most of the other cases are caused by a
destruction of the thyroid gland by the immune system."

This disease usually affects middle-aged dogs and while it is seen frequently in Golden
Retrievers, Irish Setters, and Dobermans, it can manifest in any breed.

"The first symptom that is usually seen is hair loss," remarks Dr. Henshaw. "It is usually not
associated with other skin problems." Other symptoms may include weight gain, muscle
loss, lethargy, and a tendency to seek heat (especially in winter). Pet owners usually
attribute many of these symptoms to the pet's aging process.

"This is not a life-threatening disease," says Dr. Henshaw. "If it is left untreated however, the
lethargy will get worse, the dog may experience a mental dullness, and the heart rate can

"The symptoms with hypothyroidism are usually subtle at first," she observes. "It is a gradual
process which takes months to one year to develop."

Diagnosis of this disease is done by a series of blood tests. These tests are fairly common
and can be conducted by your veterinarian.

While hypothyroidism is not a curable disease, notes Dr. Henshaw, it is very treatable. "The
treatment consists of oral supplementation of the thyroid hormone on a daily basis. It is very
safe, life-long, and relatively inexpensive. Treatment often rejuvenates a dog." Many dog
owners are familiar with hypothyroidism because it is a disease which also occurs in people.
Although there are many similarities, owners of hypothyroid dogs should follow the advice
of their veterinarian, as the dosage of thyroid hormone supplementation is very different for

Dr. Henshaw remarked that hypothyroidism can complicate other skin diseases and, if left
untreated, will affect the quality of life. Once diagnosed, there are virtually no side effects
from the drug therapy and there is very little monitoring needed. Once the hypothyroidism is
controlled with drug therapy, a dog will no longer be predisposed to other disease
conditions. Dog owners are often pleasantly surprised that their "old dog" is acting

If you would like further information or would like to have your dog tested for
hypothyroidism, contact your local veterinarian.