Diagnosis and Treatment

Diagnosis of hypothyroidism in dogs

Baseline laboratory evaluation

Complete blood count (CBC)

It is not uncommon for hypothyroid dogs to be anemic (normocytic, normochromic, nonregenerative anemia).

Clinical chemistry

Hypothyroid dogs have decreased fat metabolism and commonly have elevated blood cholesterol (hypercholesterolemia) and lipids (hyperlipidemia).

Urinalysis

This test is important for assessing whether other diseases are affecting your dog either in addition to, or instead of hypothyroidism. Urinalysis is usually normal in hypothyroid dogs.

Thyroid specific evaluation

A number of different tests are used to specifically assess thyroid gland function.

Total thyroxine (tT4)

This is usually evaluated initially. If the results of this test are within normal limits, your veterinarian will usually look for other causes of your dog’s clinical signs. Most dogs with hypothyroidism will have low values for T4 compared with healthy dogs. Dogs that have other diseases can also have low T4.

Common additional tests

Evaluation of additional tests is necessary to determine whether your dog is hypothyroid. Thyroglobulin autoantibody is particularly important in dogs intended for breeding because lymphocytic thyroiditis may be hereditary.

A dog that has primary hypothyroidism typically has a low T4, low free T4 and a higher than normal TSH concentration.

How is hypothyroidism treated?

The hallmark of treatment for hypothyroid dogs is hormonal replacement with synthetic thyroid hormone.

There is a once daily liquid and also tablets available for treating dogs with hypothyroidism. These treatments have to be given by mouth. It is important to give it at the same time every day.

If a product suitable for once daily treatment such as the liquid formulation is prescribed this may be given either in the morning or evening. Follow-up evaluation of T4 will be necessary and the blood sample is ideally drawn 4-6 hours after the treatment is given, so morning treatment is ideal for ease of blood sampling.