Anti-TPO Antibody, plasma or serum

It was first demonstrated by Trotter et al. in 1957 and subsequently by Roitt and Doniach in 1958 that many patients with Hashimoto’s thyroiditis had detectable autoantibodies in their blood directed at a thyroid antigen distinct from thyroglobulin. This antigen was termed thyroid microsomal and it has since been demonstrated that most if not all anti-thyroid microsomal autoantibodies recognize thyroid peroxidase (TPO) It is common to find anti-TPO antibodies in the absence of autoantibodies to thyroglobulin, particularly in patients with small goitres and up to 64% of cases of autoimmune hypothyroidism have been reported to be associated with anti-TPO antibodies alone.18 In addition, anti-TPO antibodies are frequently found in patients with other autoimmune diseases such as Rheumatoid Arthritis, Addison’s Disease and Type I Diabetes. They are also detectable at low levels in up to 20% of asymptomatic individuals, particularly the elderly and more often in women than in men, although the clinical significance of these autoantibodies is unclear.