Tg, TgR and TgAb concentrations were determined by fully automated two-site chemiluminescence immunoassays (CLIA; Nichols Advantage®; Nichols Institute Diagnostics, San Clemente, California). All 3 assays are based on the identical highly purified hTg material for calibration (Tg), recovery (TgR) and antigen (TgAb; biotinylated and acridinium ester labeled) for optimum comparability of test results.