OFA Thyroid Classification

The method for classifying the thyroid status will be accomplished using state-of-the-art assay methodology.

Indices of thyroiditis

1. Free T4 (FT4)—this procedure is considered to be the "gold standard" for assessment of thyroid's production and cellular availability of thyroxine. FT4 concentration is expected to be decreased in dogs with thyroid dysfunction due to autoimmune thyroiditis.

2. Canine thyroid simulating hormone (cTSH)—this procedure helps determine the site of the lesion in cases of hypothyroidism. In autoimmune thyroiditis the lesion is at the level of the thyroid gland and the pituitary gland functions normally. The cTSH concentration is expected to be abnormally elevated in dogs with thyroid atrophy from autoimmune thyroiditis.

3. Thyroglobulin Autoantibodies (TgAA)—this procedure is an indication for the presence of the autoimmune process in the dog’s thyroid.

Certification

Normal

• FT4 within normal range
• cTSH within normal range
• TgAA is negative

Positive autoimmune thyroiditis

• FT4 less than normal range
• cTSH greater than normal range
• TgAA is positive

Positive compensative autoimmune thyroiditis

• FT4 is within normal range
• cTSH is greater than or equal to normal range
• TgAA is positive

Idiopathically reduced thyroid function

• FT4 is less than normal range
• cTSH greater than normal range
• TgAA is negative

All other results are considered equivocal

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