OFA Thyroid Testing for Breeding Dogs: What Breeders Need to Know

Autoimmune thyroiditis — the most common cause of hypothyroidism in dogs — has a strong genetic component in many breeds. The OFA maintains a thyroid registry where breeders can submit thyroid panel results and certify their dogs' thyroid health status. For affected breeds, thyroid testing is an important part of a complete health testing program.

What Is Autoimmune Thyroiditis?

Autoimmune thyroiditis occurs when the dog's immune system attacks its own thyroid gland, progressively destroying thyroid tissue and reducing hormone production. The result is hypothyroidism — low thyroid function — which causes weight gain, lethargy, hair loss, cold intolerance, and other metabolic symptoms.

The disease has a heritable component: dogs from families with high rates of thyroiditis are at significantly elevated risk. Breeding two affected or carrier dogs can increase prevalence in offspring.

How OFA Thyroid Testing Works

The OFA thyroid panel consists of a blood test measuring:

• T4 (thyroxine): Total thyroid hormone level
• Free T4: The biologically active fraction of T4
• TSH: Thyroid-stimulating hormone (elevated when thyroid function is low)
• TgAA (thyroglobulin autoantibodies): The key autoimmune marker

TgAA is the most important marker for identifying autoimmune thyroiditis before clinical disease appears. A dog can have normal T4 levels but positive TgAA — meaning the immune attack on the thyroid has begun but hasn't yet reduced hormone output.

OFA Thyroid Registry Classifications

OFA classifies thyroid results as:

• Positive: Positive TgAA — evidence of autoimmune thyroiditis
• Equivocal: Borderline TgAA values — repeat in 3–6 months
• Negative/Normal: No evidence of thyroiditis at time of testing

Dogs should ideally be tested annually, as autoimmune thyroiditis can develop at any age. A negative result at age 2 does not guarantee the dog will remain negative at age 6.

Which Breeds Are Most Affected?

OFA data shows particularly high rates of thyroid disease in: Akitas, English Setters, Hounds (various), Giant Schnauzers, Boxers, Beagles, Maltese, Rhodesian Ridgebacks, and Skye Terriers. Many other breeds have elevated rates compared to the general population.

Where to Find Results

Thyroid results submitted to OFA are publicly searchable at ofa.org under the dog's registered name. Only positive and equivocal results are published on OFA open — owners can elect to keep normal results private, but most responsible breeders make them public.