Abstract: 【Abstract】Objective To explore the effects of thyroid hormone on the expression of homeobox gene Nkx2.2 in child rat and the relationship between gene expression and hormone level by supplying their hypothyroidism pregnant mother with thyroid hormone. Method 240 Wistar rats,half male and half female, were randomly divided into eight groups: normal control group,hypothyroidism group, hypothyrodism groups which were supplied with thyroid hormone in different doses in early stage(1-17d),hypothyrodism groups which were supplied with thyroid hormone in different doses in late stage(18-20d) .All the rats were fed with low-iodine food.The normal control group was given KIO3 solution and the other groups were given deionized water.After three months’raising,each group was drawn materials from the 17-day fetal rats,new-born and 20-day old offspring,and was detected the content of Nkx2.2 mRNA in afterbrain tissue by real-time fluorescence quantitative PCR techniques. Results① The expression of Nkx2.2 mRNA have significant difference between groups in 17-day fetal rats,new-born and 20-day old offsprings(F=7.080、19.007、24.652，P﹤0.01）②The time factor and dosage factor have influence on Nkx6.1 mRNA expression (F=6.992、5.939，P﹤0.01) ③Time factor and dosage factor have interaction（F=5.610，P﹤0.01）④ the expression level in low-iodine group were higher than normal group during the same period（P﹤0.05）,and it increased gradually with age.⑤ The expression of Nkx2.2 mRNA in new-born and 20-day old offsprings which were supplied with thyroid hormone in high and medium dosage in late stage is close to the normal group at the same period（P﹥0.05）.Conclusion The expression of Nkx2.2 in child rats is highly related to the supply dosage and supply time of thyroid hormone in hypothyrodism preganant rats.

Key words: Hypothyroidism, Homeobox gene, Real-time fluorescence quantitative PCR