Diagnosing and Treating Hypothyroidism in Dogs
Posted July 13, 2012
Hypothyroidism is not limited to people; it is common in dogs as
well. This problem occurs when the thyroid gland does not
produce enough thyroxine, a hormone with numerous functions such as
regulating the body's metabolic rate.
This disease is often seen in dogs that are 4 to 6 years
old. Any breed may develop this disorder, but some breeds
such as Labrador retrievers, Doberman pinschers, golden retrievers,
dachshunds, cocker spaniels, and greyhounds appear to be
Since the body's metabolic rate determines the way energy is
handled, hypothryroidism often leads to progressive weight gain
without an increase in food intake, explained Dr. Audrey Cook,
clinical associate professor at Texas A&M College of Veterinary
Medicine & Biomedical Sciences.
"Although many dogs tend to gain pounds as they age, an
unexplained increase in body weight can be a sign of low
functioning thyroid," Cook said.
Thyroxine is also important for maintenance of the skin and hair
coat. Often, the hair of a dog with hypothyroidism will grow slowly
and may change to a lighter color. The hair may appear thin all
over, particularly on the tail. Another result of the disease is
flaky skin and pigmentation in the non-haired areas.
"One of the classic signs of canine hypothyroidism is the
so-called "rat tail," in which the hair is lost from the last few
inches of the tail," Cook said.
In addition to the dog's overall appearance, hypothyroidism can
affect the pet's mental state, resulting in depression and
apathy. Other signs of the disease include sensitivity to the
cold, muscle weakness, problems with nerve function, and persistent
fatigue. Problems such as chronic skin or ear infections may
also be a sign of hypothyroidism.
"Owners often mistake the signs of hypothyroidism with the aging
process," Cook said. "However, these changes can be reversed with
effective management. Many dogs get a new lease on life when their
hypothyroidism is treated."
Veterinarians can diagnose the disease with simple blood tests.
These usually include measurement of total thyroxine levels (often
called total T4), unbound hormone levels ('free' T4), and thyroid
stimulating hormone (TSH) concentrations.
As with people, dogs with hypothyroidism can take daily oral
medication to replace the missing hormone. Once medication
for this problem begins, it is continued throughout the pet's
life. Sometimes, the dosage has to be adjusted to get the
hormone levels correct. If the thyroxine levels are too high,
dogs can lose excessive amounts of weight and appear agitated.
"We do recommend periodic checks on thyroid levels to make sure
the dose is on-target, but these tests are simple and inexpensive.
Your veterinarian will tell you when to bring your dog in for a
recheck," Cook said.
Fortunately, once the disease is diagnosed and the dog is given
the proper medication, the pet should feel better within a few
weeks. It can take a little while for the hair coat to improve, but
Cook said energy levels and body condition tend to improve quickly.
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