Front Range Animal Hospital
418 Third Street, P.O. Box 326
Monument, CO 80132-0326
(719) 481-3455

Hypothyroidism in the Dog

Hypothyroidism is an inadequate production of hormone from the thyroid gland. This is a common hormone imbalance in dogs and can result in a number of symptoms and problems. Dogs can exhibit any one or combination of these symptoms which can make it challenging to diagnose. Classic symptoms of hypothyroidism include lethargy, mental depression, weight gain, and heat-seeking tendancies but some hypothyroid dogs do not have these symptoms. Hypothyroidism commonly affects the coat and skin and can causes hair loss (balding), excessive dandruff, poor hair regrowth after clipping, increased pigment in the skin, and ear infections. Additional symptoms include muscle weakness, nervous system abnormalities, cardiac problems, reproductive disturbances, enlarged breasts, and poor immunity to infections.

Hypothyroidism is diagnosed with blood tests. Many dogs have a low "resting" thyroid hormone (T4) level in their blood stream. If the resting T4 is normal, but hypothyroidism is still suspected, a TSH stimulation test can be run. The TSH stimulation test evaluates how well the thyroid gland responds to TSH (Thyroid Stimulating Hormone). Hypothyroid dogs do not respond normally.

Hypothyroid dogs are easily treated with thyroid pills. Thyroid pills are inexpensive but must be continued daily for the rest of the petıs life. They replace the hormone the thyroid gland does not make, but do not cure the underlying gland malfunction. The lethargy and depression usually responds to pills within 2-4 weeks but skin and coat problems may take 5 months for correction. One note of warning­the coat may look worse before it improves as the old coat is shed prior to growing a healthy one.

Each dog's thyroid replacement needs is individual and can change over it's lifetime so periodic blood tests to check hormone levels are recommended, the first one about one month after the start of treatment. Schedule blood tests 4-8 hours after the pill is given to get the proper hormone levels.