Objective:To study the influence on thyroid after radiotherapy of nasopharyngeal cancer.Methods:97patients were divided into three group:(1)before radiotherapy;(2)after one course of radiother-apy;(3)after two courses of radiotherapy and their serum FT3,FT4and hTSH were measured.Results:There is significant decrease in the values of FT3,FT4after radiotherapy,but there is no significant difference in hTSH between the patients pre-radiotherapy and pro-radiotherapy.The FT3,FT4and hTSH have no sig-nificant diff...