Two types of thyroid abnormalities are defined by the OFA: autoimmune thyroiditis (hypothyroidism) and compensative autoimmune thyroiditis (hyperthyroidism).

Autoimmune thyroiditis is the most common cause of primary hypothyroidism in dogs. The disease has variable onset, but tends to clinically manifest itself at 2 to 5 years of age. Dogs may be clinically normal for years, only to become hypothyroid at a later date. Autoimmune thyroiditis is known to be hereditable.Hypothyroidism is a disorder which causes the thyroid gland to produce too little of its hormone.

Compensative autoimmune thyroiditis is a form of hyperthyroidism and is much less common than hypothyroidism.


Physical symptoms of Hypothyroidism include weight gain, hair loss, dry skin, thickened, scaly patches of skin in spots where hair has fallen out, dull and greasy coat, skin infections, ear infections, and unpleasant skin odors. Less frequently seen physical symptoms are constipation, diarrhea and vomiting. Other, non-physical, symptoms are lethargy, weakness, behavior changes, disorientation (a trance-like state), irritability, and anxiety.

In Hyperthyroidism, symptoms such as excessive sweating, anxiety, increased sensitivity to heat, insomnia, fatigue, rapid heartbeat, tremors, frequent bowel movements, and enlargement of thyroid gland may be seen.


Treatment methods include medication, radiation, and surgery. Most dogs require daily medication for their entire lives once diagnosed even if radiation or surgery have also taken place.

Test method

The test is conducted by a veterinarian. Using a sample of freshly collected blood, 2 ml of serum are extracted and sent for testing to the approved lab via overnight courier. The lab results are sent directly to the OFA.

Link to test application form:

Genetic/breeder information

Dogs may only have a certified thyroid result after the age of 12 months. As a result of the variable onset of the presence of autoantibodies, periodic testing will be necessary. Dogs that are negative at 1 year of age may become positive at 6 years of age. Dogs should be tested every year or two in order to be certain they have not developed the condition. Since the majority of affected dogs will have autoantibodies by 4 years of age, annual testing for the first 4 years is recommended. After that, testing every other year should suffice. Unfortunately, a negative at any one time will not guarantee that the dog will not develop thyroiditis.

The registry data can be used by breeders in determining which dogs are best for their breeding program. Knowing the status of the dog and the status of the dogs’ lineage, breeders and genetic counselors can decide which matings are most appropriate for reducing the incidence of autoimmune thyroiditis in the offspring.

 Stats within CdT breed

From 1974-2012 there were 520 Cotons registered with OFA for thyroid test results. 84% of these were normal, 3.8% autoimmune thyroiditis, 0.2% idiopathic hypothyroidism, and 11.9% were equivocal. Animals with equivocal results should have the testing repeated in 3 to 6 months.

 Source of data