Symptoms of Thyroid Disease in Dogs

Thyroid disease in dogs is often difficult to recognize because symptoms are so subtle. Owners might notice a change in energy level, weight gain or skin problems and associate those problems with something more mild. However, thyroid problems are easy to diagnose with a blood test and relatively easy to treat with medication once the problem is detected.

Symptoms of Hypothyroidism

Though rare in cats, hypothyroidism is a common illness in dogs in which not enough thyroid hormones are produced. The thyroid hormone has many functions, but one of the most important is regulating metabolism. Thus, as you would suspect, one of the main symptoms of hypothyroidism is weight gain.

Hypothyroidism usually isn't detected until later in the dog's life, but new research shows that 90 percent of hypothyroid cases are caused by a genetic autoimmune disease called thyroiditis, which produces antithyroid antibodies in the body and may begin to develop as early as puberty though clinical signs won't appear for years.

Hypothyroidsm most commonly affects middle aged dogs (ages 4 to 10), particularly large breed dogs. Miniature and toy breeds are rarely affected. Other symptoms include lethargy, hair loss, dry coat, excessive shedding, cold intolerance, exercise intolerance, low heart rate, high cholesterol, sudden behavioral changes such as increased aggression and anemia. Not all dogs will experience all symptoms. In fact, some may exhibit very few, mild symptoms in the early stages.

In serious cases, your dog may suffer from seizures, cardiac irregularities, corneal ulceration, loss of smell or taste or chronic hepatitis.

Symptoms of Hyperthyroidism

Hyperthyroidism is more commonly seen in cats than dogs, but some dogs still experience the condition, which causes too much thyroid hormone to be produced, unhealthily increasing your pet's metabolism. This also more regularly affects older dogs and can be a slow progression.

Symptoms include weight loss, elevated heart rate, increased urination, hyperactivity, increased irritability and increased appetite. In rare cases, your dog may become weaker with a decreased appetite and energy level. Hyperthyroidism is sometimes caused by cancer, which may cause other symptoms to appear as well.

Diagnosis and Treatment

Thyroid problems can be detected with a blood test called a complete T4 panel that measures level of thyroid hormones in the blood. The blood is sent to a lab and abnormal results will be reported to you.

Dogs that test positive for thyroid disease must have their thyroid hormones regulated with medication, such as Soloxine, for the rest of their life.

More than 50 different breeds are genetically predispositioned to develop thyroid disease, so if you have one of those breeds consider early testing to catch the disease before it causes serious damage to your dog. Though symptoms may appear mild, untreated thyroid disease can cause long-term problems.