Hypothyroidism in Dogs

Hypothyroidism is a condition in which the body lacks sufficient thyroid hormone. It is the most common endocrine disease in dogs but seems to affect some breeds more frequently. Large dogs like Labrador and Golden Retrievers are over represented but so are some predisposed mid- sized dogs like Cocker Spaniels, Poodles and Dachshunds. Hypothyroidism is more commonly seen in middle aged dogs (about 7 years).

Since the main purpose of thyroid hormone is to “run the body’s metabolism,” it is understandable that dogs with this condition will have symptoms associated with a slow metabolism. Usually owners will notice their pet is gaining weight and seems less eager to exercise (lethargic). Some dogs will also have symmetrical hair loss often in the mid back area. And some will have recurrent skin infections.

Once a differential diagnosis of hypothyroidism is made it needs to be confirmed with blood testing. General blood work can show, among other things, anemia and high cholesterol and a specific test showing low thyroid increases the likelihood. Unfortunately a low thyroid can be a false finding as it can also go down with other illnesses as the body is under stress (sick euthyroid).

Hypothyroidism is treated with daily oral medication. After an initial dose is verified by blood test 4-6 weeks after commencing treatment, dogs are retested every 6 months to ensure no changes in their medication is needed.

Written by: Jennifer Merry BSc (Agr) DVM