Abstract: Objective To study the influence of organic iodine(diiodotyrosine,DIT) and inorganic iodine(potassium iodine,KI) on expressions of a gene family about apoptosis(Fas,FasL and p53).Methods The human thyroid epithelium cells from para-adenoma normal tissues of thyroid adenoma patients were cultured and then divided into a control group(medium),KI groups(with KI at dosages of 0.1,10,and 1 000 μmol/L,respectively) and DIT groups(at the dosages of 0.1,10,and 1 000 μmol/L,respectively).Various dosages of DIT and KI diluted with medium were applied to the cells for 48 hours.The local distribution and expression of Fas,FasL and p53 of human thyroid cell were determined with immumohistochemistry after different dosages of DIT and KI treatment.Results The expression of Fas in KI groups(10,1 000 μmol/L) and DIT groups(10,1 000 μmol/L) were 0.131 8±0.010 0,0.217 4±0.017 7 and 0.124 5±0.007 4,0.158 5±0.010 0,respectively,and were significantly higher than that in the control group(0.072 8±0.009 3)(P<0.01).The expression of FasL in KI groups(10,1 000 μmol/L) and DIT groups(10,1 000 μmol/L) were 0.108 1±0.015 5,0.178 4±0.010 4 and 0.093 8±0.007 0,1 382±0.008 0,respectively,and were significantly higher than that in the control group(0.060 8±0.009 6) (P<0.01).With the increment of exposure,the expressions of Fas and FasL increased.With the same level of DIT and KI,the expression of Fas of DIT groups(1 000 μmol/L) was significantly leower,and the expression of FasL of DIT groups(10,1 000 μmol/L) was significantly lower(P<0.01).There was no significant difference among the groups in the expression of p53.Conclusion High level of iodine can increase the levels of Fas and FasL expression.And it doesn't influence the expression of p53.The effect of DIT is weaker than that of KI.