〔Abstract〕 Objective To evaluate the angiogenesis of decidua in spontaneous abortion patients and to investigate the change of thyroid hormone receptor signal expression in decidua in miscarriage patients.Methods The decidua of pregnant women was collected.Patients with miscarriage were taken as the experimental group and healthy pregnant women who underwent abortion by social factors were taken as the control group.The nuclear translocation of thyroid hormone receptor α(THR-α) and THR-β in decidua tissues was detected by Western blot method,and the distribution of THR-α and THR-β in decidua tissues was determined by immunohistochemistry.The expression of Deiodinase 2(DIO2) in decidua tissues was determined by Western blot.The distribution of DIO2 in decidua tissues was determined by immunofluorescence and the fluorescence intensity was measured.The decidual vessel density was determined by immunohistochemistry using CD34 as an endothelial marker.The protein expression of vascular endothelial growth factor receptor(VEGFR-1) was detected by Western blot.Results There was no significant difference in age,gestation days,TSH,T3,T4 and other basic data between the control group and the abortion group.The results of Western blot showed that the expression levels of THR-α and THR-β protein decreased,and the results of immunohistochemical staining of decidual tissues showed that the nuclear translocation of decidual thyroid hormone receptor in patients with spontaneous abortion decreased(P<0.05).Western blotting results showed that the expression of DIO2 protein in the abortion group was lower than that in the control group,suggesting that thyroid hormone metabolism in decidua of spontaneous abortion pregnant women was affected.The results of immunofluorescence test showed that the fluorescence intensity of DIO2 in the abortion group was weaker than that in the control group(P<0.05).Immunohistochemical CD34 labeling of decidual small blood vessels showed that the number of CD34+blood vessels decreased in the abortion group with statistical difference(P<0.05).Western blot results showed that there was no significant change in VEGFR-1 between the two groups,and the difference between the two groups was not statistically significant.Conclusion The abnormal signal of thyroid hormone receptors in decidua may decrease decidua angiogenesis and participate in spontaneous abortion.