Diagnosing Canine Hypothyroidism

Canine hypothyroidism is an autoimmune disorder that stems from thyroid gland dysfunction. The thyroid gland is a butterfly-shaped gland located at the base of the neck, and is responsible for proper metabolism. Hypothyroidism is the term used to describe a condition where the thyroid gland is underactive or secretes less than the required amount of thyroid hormone. In order to establish a correct diagnosis, it’s important to notice the symptoms of hypothyroidism in pets.

Symptoms of Canine Hypothyroidism

Pet owners often confuse the symptoms of canine hypothyroidism with other diseases. Pets suffering from an underactive thyroid gland appear lethargic or depressed. The external appearance of the dog also changes due to dry skin, loss of hair and a dull coat. Dogs suffering from hypothyroidism will have frequent ear infections, along with abnormal skin conditions and behavior changes. They may also feel cold in normal temperature and seek warmth.

Clinical Signs of Canine Hypothyroidism

Research has established that several pets suffering from hypothyroidism experience neurological changes in the brain. This is often accompanied by seizures and behavior changes such as aggression. The most common neurological changes include polyneuropathy, focal neuropathy and central nervous system changes. The nervous system in a dog consists of nerve connections that transmit electrical impulses to carry out normal body functioning. This doesn’t occur adequately in dogs suffering from hypothyroidism. Pets may also experience changes in the cornea of the eye. Although this isn’t true for every pet suffering from hypothyroidism, it occurs in pets with underlying disease.

Breeds Predisposed to Canine Hypothyroidism:

  • Beagles
  • Golden retrievers
  • Rottweiler’s
  • American cocker spaniel
  • German shepherds

Diagnosis of Canine Hypothyroidism

The diagnosis is based on a combination of symptoms and tests. Since various factors such as genetic predisposition and medical administration alter the readings of thyroid and other hormones, it’s necessary to evaluate the efficacy of diagnostic testing before administering thyroid treatment. The initial test for canine hypothyroidism involves a test known as T4. Pets that are tested positive for T4 are then recommended a T3 test and TSH test. The vet will also conduct tests such as the free T4 test and a TSH Response test.

T3 Testing

A T3 test measures the amount of tri-iodothyronine present in the dog’s blood. However, certain breeds are predisposed to lower thyroid levels and therefore require further diagnosis.

T4 Test

This test measures the amount of total protein-bound hormone present in the blood. The Free T4 test measures the amount of active thyroxine in the blood. Known drugs that reduce throxine levels are prednisone, cortisone, Phenobarbital and phenylbutazone.

TSH Test

TSH, also known as thyroid stimulating hormone, is not as effective in determining elevated TSH unless it’s compared with healthy dogs that show normal levels of TSH. The test works best when used to measure thyroid levels along with the T4 test.

TSH Response Test

In order to conduct a TSH response test, a specific amount of TSH is injected into the pet’s body and the response to it will be determined after a few hours. Pets that suffer from hypothyroidism don’t show any change to the increased TSH.

The treatment for thyroid uses synthetic thyroid hormones to alter the dog’s pre-existing thyroid levels. The vet will also schedule periodic checks to test the initial response to medication and alter the dosage.