The thyroid gland is in the neck. It makes a hormone called thyroxine that controls metabolism (the process of turning food into fuel). With hypothyroidism, the gland doesn’t make enough of that hormone.
It’s a common disease in dogs. It affects all breeds, but it is often found in golden retrievers, Doberman pinschers, Irish setters, dachshunds, boxers, and cocker spaniels. It usually happens in middle-aged dogs (ages 4 to 10) of medium to large breeds. Neutered males and spayed females also have a higher risk, but vets are unsure why.
It is thought that in some cases of hypothyroidism, your dog’s immune system attacks his thyroid. Other causes are the shrinking of his thyroid and, although rare, a tumor of the thyroid gland. No matter the cause, symptoms and treatments are the same.
Signs of hypothyroidism include hair loss, usually on your dog’s trunk, back of the rear legs, and tail. His coat will be dull and thin, his skin flaky, but not itchy or red (which is usually tied to fleas or an allergic reaction). He may also have black patches of skin. This is followed by weight gain (despite decreased appetite), muscle loss, sluggishness, a slowed heart rate, toenail and ear infections, and intolerance to cold. It’s not widespread, but hypothyroidism is also linked to seizures, heart and blood vessel problems, and infertility.
For a diagnosis, your vet will do a series of blood tests.
The good news is this disease isn’t life-threatening. Plus, it’s fairly easy and inexpensive to treat. Your dog will have to take oral drugs daily for the rest of his life. The drug is a manmade hormone called levothyroxine or L-thyroxine. Doses are specific to each dog.
Left untreated, the disease will affect your dog’s quality of life.