Hypothyroidism & Aggression in Dogs

Hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormone, affects more than 50 dog breeds and mixes. Among the symptoms of hypothyroidism are anxious or aggressive behavior that does not fit usual patterns or is excessive for the situation.

  1. Hypothyroidism

    • Hypothyroidism is an endocrine disease in which the body produces an abnormally low amount of thyroid hormones, which are needed to regulate the dog's metabolism. The severity of hypothyroidism ranges; in some situations the dog can still function normally as the thyroid hormone levels are not that low. The lower the hormone count, the lower the dog's metabolism.

    Causes

    • Hypothyroidism occurs when the dog's immune system attacks the thyroid gland---this is called autoimmune thyroiditis. At first, the thyroid gland will secrete more hormones to compensate, but it will eventually be unable to keep up with the attacks. There is a genetic disposition for this disorder, though environmental factors are thought to play a part, as well. The disease affects males and females equally and most dogs contract hypothyroidism between 4 and 10 years of age.

    Symptoms

    • Hypothyroidism is strongly linked with aggression in dogs and this symptom normally precedes other physical signs. Dogs with hypothyroidism tend to be excessively anxious or aggressive or their aggressive behavior does not follow their normal behavior patterns. Along with aggression, the dog may also be lethargic and/or depressed, leading to weight gain, slow heart rates, hair loss, dry skin and cold intolerance.

    Diagnosis

    • A blood test is required to determine the levels of thyroid hormone in the bloodstream to confirm diagnosis. There are numerous blood tests the veterinarian can employ, the most common being the baseline T4 Test or Total T4, which measures the level of the T4 hormone.

    Treatment

    • Aggressive behavior caused by hypothyroidism cannot be treated with training alone. The hypothyroidism must be treated in order to get rid of the behavioral symptom. The dog must be given a daily dose of a synthetic thyroid hormone---thyroxine---which will bring the hormone levels up and diminish the aggressive behavior; this can happen as quickly as five days or take up to four weeks. Blood samples will be taken periodically to ensure the dog is getting the needed amount of synthetic hormones.