Antibodies against Thyroglobulin (TGAA) are an indication of auto-immune activity. This will normally induce thyroid dysfunction and a decrease in free T4. These antibodies account for the majority of canine hypothyroidism, circulating auto-antibodies that bind to thyroid hormones (THAA). Higher values were found in ± 5% of dogs between 1 and 6 years old. Highest rate off positivity was found in dogs with high TSH values (± 12%). In several breeds a higher incidence was found; Golden retriever, cocker spaniel, English setter, old English sheepdog, boxer, Shetland sheepdog and Beagle.