Abstract MTP-1
AUTOIMMUNITY AND THYROID CARCINOMA ROSSELLA ELISEI Associate Professor of Endocrinology, University of Pisa
Thyroglobulin (Tg) is a protein produced and secreted only by thyroid cells. Its production is maintained also by tumoral cells in well differentiated thyroid cancer (DTC) such as papillary (PTC) and follicular (FTC) hystotype. Since many years, it has been recognized as the most sensitive and specific marker of residual thyroid tissue and/or persistence/recurrence of the disease in patients affected with DTC and treated with total thyroidectomy (TTx) and post-operative remnant ablation (RRA) with radioiodine (131I). However, approximately 25-30% of patients with DTC have serum thyroglobulin antibodies (TgAb) which interfere with Tg measurement, causing either false negative (by immunometric assays) or false positive results (by radioimmunological assays). TgAb are the expression of an associated lymphocytic thyroiditis (LT) or the expression of an immune reaction to DTC. In these cases, serum Tg loses its function as tumor marker, but the change of the serum TgAb levels over the time can be used as a “Tg surrogate” since it has been demonstrated that in cured DTC patients, the TgAb levels decline to reach the negativization. At the same time, the persistence of stable levels of TgAb for a long period of time or the increase of TgAb levels after TTx plus/minus RRA represent an alert about the possibility of persistence or recurrence of DTC. Currently, this concept is so well established that the new international referral guidelines for the management of DTC include the TgAb evaluation after initial treatment as essential to assess the ongoing risk stratification.
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