Context: The mechanisms linking thyroid autoimmunity and iodine use in humans are unknown. Objective: Our aim was to correlate iodine intake, thyroid autoimmunity, and recognition of thyroglobulin (Tg) epitopes after implementation of iodine prophylaxis. Setting: The general community living in an Italian village was evaluated. Main Outcome Measures: Thyroglobulin autoantibodies (TgAb), thyroperoxidase autoantibodies (TPOAb), and urinary iodine excretion were assessed in 906 iodized salt users (IS-users) and 389 nonusers (IS-nonusers). Ultrasound (US) was performed to identify thyroid hypoechogenicity, sug- gestive of Hashimoto thyroiditis (HT). TgAb epitope pattern in 16 IS-users and 17 IS-nonusers was evaluated by an inhibition binding assay to Tg, using human monoclonal TgAb-Fab directed to A, B, C, and D epitopes on Tg. Results: Median urinary iodine excretion was slightly higher in IS-users than in IS-nonusers (112.0 g/L vs 86.5 g/L; P .01). TgAb, and not TPOAb, was more frequent in IS-users (18.9% vs 13.6%, P .02). HT-US was found in 87 subjects, among whom both positive TgAb (58.4% vs 31.8%, P .03) and TPOAb (61.5% vs 45.4%. P .04) were more frequent in IS-users. In this group significantly higher serum levels of TgAb (median 108 U/mL vs 30 U/mL; P .02), but not of TPOAb, were present. Iodized salt use had no effect on the 1208 non HT-US subjects. TgAb directed to the epitope B of Tg were more frequent in IS-users than in IS-nonusers (27.5% vs 3.0%, P .047). Conclusions: Iodine-induced thyroid autoimmunity is related to TgAb and the unmasking of a cryptic epitope on Tg contributes to this relationship in humans.

Iodine contributes to thyroid autoimmunity in humans by unmasking a cryptic epitope on thyroglobulin.

LATROFA, FRANCESCO;FIORE, EMILIO;RAGO, TERESA;PROVENZALE, MARIA ANNATERESA;SCUTARI, MARIA;TONACCHERA, MASSIMO;VITTI, PAOLO
2013

Abstract

Context: The mechanisms linking thyroid autoimmunity and iodine use in humans are unknown. Objective: Our aim was to correlate iodine intake, thyroid autoimmunity, and recognition of thyroglobulin (Tg) epitopes after implementation of iodine prophylaxis. Setting: The general community living in an Italian village was evaluated. Main Outcome Measures: Thyroglobulin autoantibodies (TgAb), thyroperoxidase autoantibodies (TPOAb), and urinary iodine excretion were assessed in 906 iodized salt users (IS-users) and 389 nonusers (IS-nonusers). Ultrasound (US) was performed to identify thyroid hypoechogenicity, sug- gestive of Hashimoto thyroiditis (HT). TgAb epitope pattern in 16 IS-users and 17 IS-nonusers was evaluated by an inhibition binding assay to Tg, using human monoclonal TgAb-Fab directed to A, B, C, and D epitopes on Tg. Results: Median urinary iodine excretion was slightly higher in IS-users than in IS-nonusers (112.0 g/L vs 86.5 g/L; P .01). TgAb, and not TPOAb, was more frequent in IS-users (18.9% vs 13.6%, P .02). HT-US was found in 87 subjects, among whom both positive TgAb (58.4% vs 31.8%, P .03) and TPOAb (61.5% vs 45.4%. P .04) were more frequent in IS-users. In this group significantly higher serum levels of TgAb (median 108 U/mL vs 30 U/mL; P .02), but not of TPOAb, were present. Iodized salt use had no effect on the 1208 non HT-US subjects. TgAb directed to the epitope B of Tg were more frequent in IS-users than in IS-nonusers (27.5% vs 3.0%, P .047). Conclusions: Iodine-induced thyroid autoimmunity is related to TgAb and the unmasking of a cryptic epitope on Tg contributes to this relationship in humans.
Latrofa, Francesco; Fiore, Emilio; Rago, Teresa; Antonangeli, L; Montanelli, L; Ricci, D; Provenzale, MARIA ANNATERESA; Scutari, Maria; Frigeri, M; Tonacchera, Massimo; Vitti, Paolo
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/583676
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