ABSTRACT
BACKGROUND: Since various thyroid diseases have dominant prevalence in women, it has been suggested that female sex hormone have important role on thyroid cell physiology. Interestingly, many thyroid disorders are newly diagnosed or changed their course around the period of high estrogen status, such as pregnancy. In this study, we questioned whether high concentration of estrogen could modulate thyroid cell function. METHODS: We treated normal rat thyroid FRTL-5 cell line with different time and concentration of estradiol. Using cell count, FACscan, and Northern blot analysis, we compared the changes of cell growth, cell cycle progression and thyroid specific genes expression. To evaluate the influence of thyroid stimulating hormone (TSH), all experiment was designed as two different sets, with (6H) or without TSH (5H). RESULTS: The concentration of 10-1000 nM estradiol had definite stimulatory function on thyroid cell growth in 5H condition as concentration dependent manner. FACscan revealed the increased cell growths were related to G1/S progression. The Pax-8, TTF-1 and NIS gene expressions were dramatically increased in 10-1000 nM of estradiol, too. With TSH (6H), however, we could not find any cell growth stimulating effects with 10-1000 nM of estradiol. CONCLUSION: High concentration of estradiol is one of important control factor for thyroid growth and thyroid specific genes expression, especially in 5H condition. It indicate that exposure to high concentration of female sex hormone, such as pregnancy, can be a direct stimulating factor to various thyroid function and related to autoimmune or nodular thyroid diseases around the period of pregnancy.