Hypothyroidism in Dogs
Dr. Bari Spielman
Lethargy, lack of interest in play, increased amounts of sleeping
What To Watch For
A deficiency of thyroid hormone affects the metabolic function of many organ systems. As a result, the clinical signs are usually variable, non-specific, and slow to develop. Although there is no one symptom that is diagnostic, several combined signs may make your veterinarian more suspicious. Symptoms may include:
Depression, mental dullness
Exercise intolerance (tires easily)
Weight gain (without an apparent increase in appetite) and obesity
Cold intolerance – seeks out warm places to lie down, low body temperature
Slow heart rate (bradycardia)
Infertility, persistent anestrus (lack of heat cycles)
Chronic skin disorders, such as dry skin (seborrhea), thinning of the hair coat, excessive hair loss
Possibly other neurologic signs such as weakness, trouble walking, seizures, head tilt, facial drooping or changes in the bark.
Possibly other hormonal abnormalities including dwarfism, delayed dental eruption, mental retardation, and/or short limbs. These signs are uncommon.
Hypothyroidism is not always a simple, straightforward disease to diagnose. Various tests are available to diagnose the condition and a combination of tests may be required. Proper diagnosis also includes a thorough history, documentation of clinical signs, a thorough physical examination, and diagnostic tests to assess various organ functions, including thyroid function.
A diagnostic work-up may include the following:
Complete blood count (CBC)
Thyroxine (T4) level, free-T4 level
Canine TSH test
Thoracic (chest) and abdominal radiographs (X-rays) in certain cases
Fortunately, hypothyroidism is easily treated and involves the administration of daily doses of synthetic thyroxine. Once treatment is started, it must usually be continued for the rest of the dog's life.
At home, administer all prescribed medication(s) and observe your dog closely for recurrence or improvement in the clinical signs. Over dosage with thyroid medication causes signs of hyperactivity and weight loss. Your veterinarian may schedule periodic blood tests to measure the levels of thyroid hormone in order to monitor whether the dosage being given is adequate.
There are no effective ways to prevent hypothyroidism. However, once treatment begins, many symptoms resolve within several weeks.