Canine Hypothyroidism

What is Canine Hypothyroidism?

Canine hypothyroidism is an endocrine disorder caused by a deficiency in production of thyroid hormone. Thyroid hormone regulates metabolism; this in turn effects the rest of the body systems. Hypothyroidism is one of the more common endocrine disorders seen in dogs. Typically it affects middle aged dogs; females more than males. There may be a genetics role in the development of hypothyroidism. Certain breeds such as Golden Retrievers, Doberman Pinschers, Irish Setters, Cocker Spaniels, Boxers, Miniature Schnauzers, Dachshunds and Poodles are predisposed to the condition.

What are the signs of hypothyroidism?

You might notice such things as weight gain despite normal food intake, lethargy and weakness. As the condition progresses, you may see other symptoms such as poor skin coat (dull or dry coat, oily skin, scales), hair loss or slow hair regrowth, ear and skin infections, cold intolerance, diarrhea, constipation, fatty deposits in the eye, and occasionally seizures. Clinical signs are slow to develop and many pet owners don't notice the problem until it is fairly advanced. Your veterinarian will notice the more subtle changes during your pets annual physical exam and may recommend thyroid testing if there is any suspicion of the disease.

What causes hypothyroidism?

It is the result of decreased production of thyroid hormone due to destruction or degeneration of the thyroid gland. In most cases the degeneration is caused by an immune system disorder in which the body produces antibodies directed against the thyroid gland. This is called lymphocytic thyroiditis. In other cases the cause of the shrinkage is unknown. This is called idiopathic atrophy. A small number of cases of hypothyroidism are related to disease within the pituitary gland. The pituitary is the master gland that directs the activities of the other glands of the body. In addition, hypothyroidism can be induced by prolonged administration of steroids.

How do I know if my dog has hypothyroidism?

Hypothyroidism must be diagnosed by your veterinarian. A blood test is taken to measure the level of thyroid hormone. Other blood tests may be performed to evaluate other body systems. Sometime other diseases such as Cushing's disease (characterized by an abnormal production of steroids) or Diabetes can cause low levels of thyroid hormone. If this is the case, controlling these other disease processes usually eliminates the need for hypothyroidism treatment. Other systemic illnesses such as kidney and liver problems, heart failure, or immune system disorders can falsely lower thyroid levels. This is known as the euthyroid sick syndrome.

How will my veterinarian treat hypothyroidism?

Once the incidence of hypothyroidism has been confirmed, your veterinarian will prescribe a synthetic form of thyroid hormone called levothyroxine. The medication must be given once or twice daily for the rest of your dog's life. Activity usually improves after 7 to 10 days of treatment; however, improvement of skin conditions may take up to 6-8 weeks. The first few months of treatment require repeated blood tests to adjust dosage of medication being given. After the correct dosage is achieved, your veterinarian will recommend regular blood tests to monitor the condition. If your pet is not treated, it will continue to exhibit the signs of hypothyroidism. Spontaneous remission is not likely to occur. The good news is that with the proper veterinary treatment your dog can live a long healthy life.

by William M. Fraser, D.V.M.

petEncyclopedia | Contact Us