Diagnosis and Treatment

How is hypothyroidism diagnosed?
Although clinical signs can be suggestive of hypothyroidism, it is necessary for a veterinarian to evaluate lab work to confirm the diagnosis. A baseline evaluation will include a complete blood count (CBC), blood chemistries, and urinalysis. In addition, there are several blood tests that specifically assess the function of the thyroid gland including T4, free T4, T3, free T3, reverse T3, TSH concentration and antibody tests for lymphocytic thyroiditis.


Measurement of the T4 concentration in the blood is usually evaluated as the initial test for hypothyroidism. If the dog’s T4 is within normal limits, the veterinarian will usually look for other causes of the dog’s clinical signs, particularly if the signs do not suggest hypothyroidism. Most dogs with hypothyroidism will have low values for T4 when compared with healthy dogs. Sometimes dogs that have other diseases will also have low T4 levels, so evaluation of additional thyroid tests is necessary to know conclusively whether the dog is hypothyroid. The dog that is truly hypothyroid typically has a low T4 or low free T4 and a higher than normal TSH concentration. Evaluation for thyroid autoantibodies reveals to the veterinarian and pet owner whether the dog’s hypothyroid condition is due to lymphocytic thyroiditis. This is an important piece of information for breeding dogs, because the tendency for lymphocytic thyroiditis may be hereditary and ideally should not be passed on to the next generation.

 

Evaluation of the baseline profile also aids in the diagnosis of hypothyroidism. In hypothyroid dogs, it is not uncommon for the CBC to reveal anemia, technically referred to as a normocytic, normochromic, nonregenerative anemia. On the chemistry profile, it is common for hypothyroid dogs to have an elevated blood cholesterol (hypercholesterolemia) and lipid count (hyperlipidemia) because hypothyroidism results in a decrease in fat metabolism. The urinalysis usually is normal in hypothyroid dogs but is important for assessing whether other diseases are affecting the dog either in addition to, or instead of hypothyroidism.

 

How is hypothyroidism treated?
There is no cure for hypothyroidism, but it is a disease that is easily managed. The hallmark of treatment for hypothyroid dogs is hormonal replacement with synthetic thyroid hormone. The recent availability of LEVENTA® oral solution for the long-term management of hypothyroidism introduces a new factor of convenience for busy pet owners faced with the need to treat their dog continuously. LEVENTA® oral solution, which contains levothyroxine sodium, a synthetic form of thyroid hormone, is given to dogs once every day. LEVENTA® oral solution is available as a liquid making it easy to give, especially to dogs that are difficult to pill.

 

Leventa oral solution may be given either in the morning or evening depending on convenience; however it is important to consistently give it at the same time every day. Follow-up evaluation of T4 will be necessary and the blood sample is ideally drawn 4-6 hours after the dose of LEVENTA® oral solution is administered, so morning LEVENTA® oral solution treatments are ideal for ease of blood sampling.