Hypothyroidism in Canines: An Exploration by Dr. Catherine Barnette, DVM, Examined and Approved by Certified Veterinary Technician Emily Oliver on July 31, 2025. Published on July 21, 2023. Sharing options available on Facebook, Twitter, Email, and Print.
Hypothyroidism is a common endocrine disorder in dogs, characterised by a slow metabolism that can lead to a range of symptoms, including lethargy, weight gain, skin issues, and behavioural changes. This condition, which affects a majority of hypothyroidism cases in dogs, has no preventative measures, but early detection and treatment can significantly improve a dog's quality of life.
Symptoms and Causes
Common symptoms of hypothyroidism in dogs include excessive shedding and dry, flaky skin, weight gain without increased appetite, lethargy, reduced interest in exercise and play, intolerance to cold, behavioural changes such as depression, anxiety, or aggression, seizures (less common), slow heart rate, and recurring infections.
Hypothyroidism in dogs is primarily caused by primary hypothyroidism, which results from thyroid gland dysfunction, often due to thyroiditis (inflammation) or atrophy where thyroid tissue is replaced by fat. Secondary causes include a lack of thyroid-stimulating hormones from the pituitary gland or hypothalamus, which regulate thyroid hormone production.
Certain breeds are more prone to hypothyroidism, with middle-aged dogs (4 to 10 years) being at a higher risk. Breeds like Golden Retriever, Doberman Pinscher, Dachshund, Cocker Spaniel, Miniature Schnauzer, Irish Setter, and others are more commonly affected. Toy breeds are less commonly affected.
Diagnosis and Treatment
A veterinary diagnosis is essential before starting therapy, typically involving thyroid hormone panel testing for total and free T4 and TSH levels. The starting dose of levothyroxine, a synthetic thyroxine supplement given orally, is calculated based on a dog's weight and current thyroid levels.
Treatment primarily involves lifelong oral administration of levothyroxine, which replaces the deficient hormone and helps regulate metabolism. Monitoring response to therapy and adjusting dosage as needed is important to manage symptoms effectively.
While some owners may seek natural supplements or dietary changes, these should never replace prescribed thyroid hormone therapy. Untreated hypothyroidism can seriously impact a dog's quality of life, but with consistent veterinary care and medication, dogs with hypothyroidism can go on to live normal, healthy lives.
Ongoing Management
A dog will remain on levothyroxine for the rest of their life, and their Total T4 level is assessed every 6-12 months to ensure the correct dosage is being administered. Hypothyroidism in dogs does not typically require any specific dietary requirements.
The cost of treating hypothyroidism in dogs is relatively inexpensive, with levothyroxine costing $20-$50 per month and thyroid testing costing $50-$100. To prevent congenital hypothyroidism, avoid breeding pets with this condition. Early treatment is essential to prevent permanent effects in the case of congenital hypothyroidism, which is rare in dogs.
In summary, hypothyroidism in dogs is a manageable condition with the right veterinary care and treatment. With consistent treatment, dogs with hypothyroidism can go on to live normal, healthy lives. Overweight dogs with hypothyroidism may even lose their excess weight once their thyroid hormone levels are normal.
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