FRTL-5 (Fisher Rat Thyroid Cell Line in Low Serum %5) cells grow in the presence of TSH and show the functional properties of thyroid cells. The aim of this study was to determine the thyroid stimulating antibodies (TSAb) in Graves disease by the bioassay method based on the iodide uptake of the cells and also to determine FRTL-5 cells role as a prognostic aid in the treatment of Graves disease. Eighteen Graves patients ( male:6, female:12 ) with an average age of 36 ( 25-56 ) years were included in the study. Free thyroxine (fT4), total triiodothyronine (TT3), thyrotropin (TSH) levels were obtained and thyroid seans were performed by using Tec99m. TSAbs were determined by I125- uptake of FRTL-5 cells. I125 uptake index (IUI) was calculated by dividing each sample's I125 uptake by controls I125 uptake. IUI>1 was accepted as an indicator of the existence of TSAb. More patients with IUI>1 were found among the newly diagnosed Graves compared to the ones who were in remission ( p <0.017 ). Higher incidence of IUI> 1 was also found in patients with positive antimicrosomal antibodies.
This study indicates that FRTL-5 cells provide a reliable method of detecting TSAbs in Graves disease.
Keywords: FRTL-5, Graves disease, TSAb, iodide uptake