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Is your dog sleepy? Putting on weight? Losing hair? Lying in front of the heater all the time? These are the classic signs of a disease called Hypothyroidism, which is a very common disorder of the thyroid gland, affecting approximately 0.2% of all dogs. Signs develop gradually and spread widely.

What Is Hypothyroidism?

The thyroid gland is located either side of around a dog’s larynx and its function is to produce a hormone called thyroxine, which regulates the metabolism rate of most tissues in the body. A thyroxine deficiency due to an affected thyroid gland causes cell function to decrease, impacting on several of the body’s organ systems.

Signs Of Hypothyroidism

  • Lethargy
  • Depression
  • Gets tired easily from exercise
  • Sleeping a lot more than usual
  • Change in behaviour or disposition
  • Gaining weight despite no other changes to your dog’s lifestyle and diet
  • Seeks warmth frequently
  • Loses hair gradually, especially from the tail and spreading slowly through the rest of the body.

Complications From Hypothyroidism

Complications can arise if the hypothyroidism is not treated. Several skin issues can occur ranging from hair loss, dry coat, poor skin healing and increased occurrence of bacterial skin and ear infections. The heart will beat more slowly, becoming weaker over time. The nervous and muscular system can also be affected, leading to paralysis, poor reflexes and general weakness.

Regurgitation (passive vomiting) after meals can also occur, due to food not passing into the stomach properly due to muscle weakness in the esophagus.

Causes Of Hypothyroidism

This can vary from dog to dog, ranging from having insufficient iodine in the diet, to cancer or even an infection. In 90% of dogs, the cause is not able to be determined.


A thorough check-up from your local veterinarian is needed, followed by a series of blood tests. Sometimes ultrasounds may also be performed on the heart.

Treatment and Outcome

Fortunately, hypothyroidism can be easily managed with hormone supplementation, and the outcome is usually excellent. Dogs can live a full and healthy life as long as they receive their hormone supplementation for the rest of their lives, with the dosage as directed by their veterinarian.

Additional Information

Veterinary Partner
The Pet Health Library: Hypothyroidism in Dogs
Dr. Wendy C. Brooks, DVM, DipABVP


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