Prevalence of autoantibodies to thyroperoxidase in patients with various thyroid and autoimmune diseases.

An original radioimmunoassay for quantitation of circulating autoantibodies (aAb) to thyroperoxidase (TPO) proved to be well suited for large scale routine testing. The present study was aimed to assess the prevalence of aAb to TPO in patients with various thyroid and autoimmune disease and, for comparison, in women referred for reproductive disorders and indication of in vitro fertilization. Anti-TPO aAb were measured in sera from 32 healthy subjects and 262 patients thoroughly investigated for thyroid dysfunction. As determined in healthy subjects, the normal level of aAb to TPO in serum ranged from 0.30 to 3.07 mg/l (of affinity-purified) anti-TPO aAb. Anti-TPO and anti-MIC aAb levels were both normal in 115 patients and correlated well (r = 0.835, P less than 0.001) in the remaining 147 patients. Coexistence of normal level of anti-TPO aAb and abnormal level of anti-MIC aAb was found in 4 patients and ascribed to a lack of specificity or sensitivity of the test for anti-MIC aAb. Coexistence of abnormal level of anti-TPO aAb and normal level of anti-MIC aAb was found in 67 patients of whom 62 presented only slightly elevated (3.1 to 10.0 mg/l) anti-TPO aAb concentration; the 5 remaining patients, all with overt thyroid autoimmune disease, showed anti-TPO levels between 10.7 to 100.7 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)