Abstract: ObjectiveTo investigate the influence of DIT on the proliferation of human thyrocytes and compare DIT with KI.To study a good kind of supplement to USI that was safe and effective.MethodsThe human thyroid epithelium cells from para-adenoma normal tissues from thyroid adenoma patients were cultured in the absence or presence of 10^-8~10^-3 mol/L DIT or KI.MTT method was employed to obtain the proliferation of cultured human thyrocytes.ResultsKI of middle and high dose can inhibithuman thyrocytes to proliferate and exhibit dose-effect and time-effect relationships.DIT of only high dose can inhibithuman thyrocytes proliferate.In the same dose of DIT and KI,the effect of DIT was less than KI on inhibition of cell proliferation.ConclusionHigh concentration of iodine can inhibithuman thyrocytes to proliferate and the effect of DIT is less than KI.DIT has more security than KI.