Evaluation of thyroid stimulating immunoglobulin (TSI) in patients submitted to radioiodine therapy for Graves' disease

Abstract

Graves' disease (GD) is the main cause of hyperthyroidism, due to the presence of immunoglobulins, IgG1 subclass, directly against the TSH receptor (TSHR). Patients with GD present antibodies against TSHR (TRAb), divided into stimulators (TSI) and blockers and apoptotic (TBI). The balance between the blocking and inhibitory antibodies determines the degree of thyroid function. With the development of TRAb immunoassays and bioassays, GD diagnosis became more accurate. However, the accuracy in follow-up during clinical treatment and the prognosis of patients with GD remains undefined.Treatment with radioiodine (RIT) for patients with GD causes destruction of the thyroid, leading to greater exposure to thyroid antigens. To date, it is not known whether the elevation of TRAb is due to the higher concentration of specific stimulatory antibodies or other antibodies (neutral or inhibitory).We will evaluate 125 patients with GD and indication of RIT before and after 30, 90, 180 days and 1 year regarding thyroid function, antithyroid antibodies (anti-TPO and anti-Tg) and TRAb and TSI and correlate with clinical data and the time of hypothyroidism. Using a specific methodology for TSI, we postulate that its determination after RIT may help the clinician to early evaluate his patient with GD, regarding the persistence of hyperthyroidismand prognosis of this chosen treatment. (AU)