Hypothyroidism in Dogs

Written by Sarah Higney, Veterinary Technician
Mclean Animal Hospital

Hypothyroidism is a clinical condition that dog’s get when their thyroid glands are underactive and don’t secrete enough Thyroxine (T4) and Triiodothyronine (T3).

Thyroid glands regulate your metabolism and when they become under active and the result is a slower metabolism.  There are two separate glands that are located on either side of the trachea and are often described as looking like deflated balloons.

Hypothyroidism is usually diagnosed in dog’s 7 years of age or older and is usually caused by destruction of the thyroid glands, overtime due to inflammation or progressive failure to produce the hormones.  Not all breeds are exempt but it’s most commonly seen in Golden Retrievers, Labrador Retrievers, Cocker Spaniels, Doberman Pinschers and Boxers.

After being diagnosed through a blood test, hypothyroidism is easy to manage.  Your pet will be put on a synthetic hormone. There is no cure and your pet will need to take the medication for life.  Repeat blood work is needed to ensure that the thyroid medication is supplementing properly and dose changes can occur, pending the results. Though not usually fatal, if left untreated the thyroid tissue is destroyed and the gland cannot function anymore. Hypothyroidism affects the whole body and in time it can lead to issues that will compromise your dogs’ length and quality of life.

Signs of hypothyroidism can easily be confused with other issues such as obesity, allergies, old age and arthritis. The most common symptoms are weight gain without over feeding.  When hormone levels are low, hair grows slower and will thin and/or fall out, more noticeably on the back of his hind legs, lumbar spine and your dog may even develop a “rat tail”.  You may notice that the hair coat looks dull and may even change color.  Skin becomes flaky and dark in color due to excess pigmentation. This can also cause the skin to become oily and thickened.  They can experience a decrease in body temperature, heart rate and blood pressure. You may notice lethargy, not wanting to play, sleeping more and your dog becoming more easily fatigued.  Toenails may break, chip and become infected more easily.  In rare cases mental alertness is affected and you may find that your dog doesn’t learn as well as he once did.  He can also become constipated, suffer from diarrhea, become anemic, endure muscle weakness or even atrophy (muscle loss).  Some dogs can even experience swelling of the tissues due to fluid retention.

Once on medication for a few months, these symptoms will subside and will not be noticeable to you or your dog.  The weight loss is always a gradual process but the key is to feed a balanced diet and measure according to the food and weight of your dog.

We  are very familiar with Hypothyroidism and treatment and long term care at Mclean Animal Hospital.  If you have any concerns about your pet, please do not hesitate to call us at 416-752-5114 with any questions or to book an appointment.

Thank you for reading!