Hypothyroidism in Canines: A Comprehensive Look, Written by Catherine Barnette, DVM, and Reviewed by Emily Oliver, CVT on 07/31/2025. Published on 07/21/2023. Sharing options include Facebook, Twitter, Email, and Print.
Hypothyroidism, a common endocrine disorder in dogs, is treatable with levothyroxine, a synthetic thyroxine supplement. This condition, characterised by a metabolic slowdown, skin and coat problems, lethargy, and weight gain, is primarily caused by dysfunction of the thyroid gland.
Recognising the Symptoms
Common symptoms of hypothyroidism in dogs include weight gain without increased appetite, lethargy and decreased energy, excessive shedding, dry skin, and a dull or flaky coat. Other signs may include hair loss, skin infections and sores, sensitivity to cold and heat-seeking behaviour, slow heart rate, behavioural changes such as depression, anxiety, aggressive behaviour, or cognitive decline, constipation, and seizures in some cases.
Causes of Hypothyroidism
The causes of hypothyroidism in dogs are usually related to thyroid gland dysfunction, often due to thyroiditis (inflammation of the thyroid gland), atrophy or destruction of thyroid tissue, malfunction of the immune system attacking the thyroid gland, shrinking or underproduction of the thyroid gland, or less commonly, pituitary or hypothalamic dysfunction affecting stimulation of the thyroid gland. Rare cases include thyroid tumors.
Treatment and Management
Treatment options primarily involve daily oral thyroid hormone replacement therapy, typically with synthetic levothyroxine or thyroxine. This treatment compensates for the low hormone production and is typically required for the lifetime of the dog. Proper dosing usually results in significant improvement of symptoms.
The starting dose of levothyroxine is calculated based on a dog's weight and current thyroid levels. One month after starting treatment, a dog's Total T4 level is assessed to determine if a dose adjustment is needed. Most dogs take levothyroxine twice daily, but once-daily dosing may be adequate in some cases. The cost of levothyroxine typically ranges from $20-$50 per month, depending on a dog's weight and dosage.
Prevention and Early Detection
Early treatment is essential to prevent permanent effects in cases of congenital hypothyroidism, which is rare in dogs. Thyroid testing, performed once or twice yearly, costs $50-$100. There is no effective way to prevent acquired hypothyroidism, which constitutes the majority of hypothyroidism cases. To prevent congenital hypothyroidism, avoid breeding pets with this condition.
With treatment, the harmful effects of hypothyroidism can be completely reversed, and affected dogs typically go on to live normal, healthy lives. Dogs with hypothyroidism do not typically have specific dietary requirements, but overweight dogs may begin to lose excess weight once their thyroid hormone levels are normal.
It's important to note that while some natural supplements may support overall health, they are adjuncts, not replacements for hormone therapy.
Dogs commonly affected are middle-aged (4–10 years) and certain breeds show higher susceptibility, including Golden Retrievers, Doberman Pinschers, Miniature Schnauzers, and others.
In summary, hypothyroidism in dogs is a treatable endocrine disorder characterized by metabolic slowdown, skin and coat problems, lethargy, and weight gain, with life-long treatment centered on thyroid hormone supplementation. Regular thyroid testing and prompt treatment can ensure a positive outcome for affected dogs.
