Estradiol decreases iodide uptake by rat thyroid follicular FRTL-5 cells

Estradiol has well-known indirect effects on the thyroid, A direct effect o f estradiol on thyroid follicular cells, increasing cell growth and reducin g the expression of the sodium-iodide symporter gene, has been recently rep orted, The aim of the present investigation was to study the effect of estr adiol on iodide uptake by thyroid follicular cells, using FRTL-5 cells as a model, Estradiol decreased basal iodide uptake by FRTL-5 cells from contro l levels of 2.490 +/- 0.370 to 2.085 +/- 0.364 pmol I-/mug DNA at 1 ng/ml ( P<0.02), to 1.970 +/- 0.302 pmol I-/<mu>g DNA at 10 ng/ml (P<0.003), and to 2.038 +/- 0.389 pmol I-/<mu>g DNA at 100 ng/ml (P<0.02). In addition, 1 ng /ml estradiol decreased iodide uptake induced by 0.02 mIU/ml thyrotropin fr om 8.678 +/- 0.408 to 7.312 +/- 0.506 pmol I-/<mu>g DNA (P<0.02). A decreas e in iodide uptake by thyroid cells caused by estradiol has not been descri bed previously and may have a role in goiter pathogenesis.