Atrophic autoimmune thyroiditis: relationship between the clinical state and intrathyroidal iodine as measured in vivo in man.

The intrathyroidal iodine (ITI) was measured by means of the x-ray fluorescence method in 58 patients suffering from atrophic autoimmune thyroiditis (AAT). They were divided into 4 groups according to their basal T4, basal TSH, and the peak TSH response after TRH administration. Forty-eight normal subjects served as controls. A progressive fall of ITI was found, with less ITI in the first grade AAT patients as compared to the controls. A negative correlation between basal TSH and ITI could be shown. These data support the concept of a graded evolution of AAT, linking the clinical state to the ITI. The results also suggest that, with the hemagglutination techniques used for the determination of antithyroglobulin antibodies and antithyroid microsomal antibodies, positively at a dilution of 1:25 and 1:100, respectively, should be regraded as significant.