<P> Blocking TRAbs (also known as Thyrotropin Binding Inhibitory Immunoglobulins (TBII)) competitively block the activity of TSH on the receptor . This can cause hypothyroidism by reducing the thyrotropic effects of TSH . They are found in Hashimoto's thyroiditis and Graves' disease and may be cause of fluctuation of thyroid function in the latter . During treatment of Graves' disease they may also become the predominant antibody, which can cause hypothyroidism . </P> <P> The clinical and physiological relevance of neutral antibodies remains unclear . However, they may be involved in prolonging the TSH receptor halflife . </P> <P> Thyroglobulin antibodies are specific for thyroglobulin, a 660kDa matrix protein involved in the process of thyroid hormone production . They are found in 70% of Hashimoto's thyroiditis, 60% of idiopathic hypothyroidism, 30% of Graves' disease, a small proportion of thyroid carcinoma and 3% of normal individuals . Anti-TPO antibodies are present in 99% of cases where thyroglobulin antibodies are present, however only 35% of anti-TPO antibody positive cases also demonstrate thyroglobulin antibodies . </P> <P> Anti-Na / I symporter antibodies are a more recent discovery of possible thyroid autoantibodies and their role in thyroid disease remains uncertain . They are present in approximately 20% of Graves' disease and 24% of Hashimoto's thyroiditis . </P>

Antibodies against tpo and tg are of what immunoglobulin class