Updated October 13, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Early hypothyroidism in dogs is easy to miss because signs develop slowly: gradual weight gain, less energy, a duller coat, and seeking warm spots. It’s most common in middle-aged, medium to large dogs, with breeds like Golden Retrievers, Doberman Pinschers, Irish Setters, Cocker Spaniels, and Boxers at higher risk. If your dog shows several of these changes, ask your vet about testing.
Early signs
- Weight gain without eating more
- Slowing down or tiring on walks
- Seeking heat, disliking cold
- Duller, thinner, or slow-growing coat
- Mild skin or ear infections that keep coming back
Why testing matters
- These signs overlap with aging and other diseases
- A dog that’s sick for another reason can have low thyroid results without true thyroid disease
- Accurate testing avoids unnecessary lifelong medication
Next steps
- Bloodwork including thyroid tests
- Follow-up testing if results are borderline
More: thyroid problem symptoms.
Sources
- Merck Veterinary Manual: Hypothyroidism in dogs
- Scott-Moncrieff JC. Clinical signs and concurrent diseases of hypothyroidism in dogs and cats. Vet Clin North Am Small Anim Pract. 2007
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.