Serum TG was measured using a commercial radioimmunoassay kit (Ab-Beads Thyroglobulin, Eiken, Tokyo, Japan). Intrassay variability was 8.6% at 5 µg l -1 . Interassay variabilities across a 1month period were 11.8%, 7.4%, 3.1% at 15, 15, 50 µg l -1 , respectively. Assay sensitivity as determined from the 20% interassay coefficient of variation (CV) was 0.5 µg l -1 . The cut off level of this kit was 28.4 µg l -1 . Serum anti-TG antibody was detected with a semi-quantitative microtitre particle agglutination test for the in vitro diagnostic detection and titration of anti-TG antibodies in human serum, SERODIA-ATG (Fujirebio, Tokyo, Japan).