Objective:To study the safety of mifepristone on thyroid hormone level by using hyperthyroidism pregnant model in mouse to simulate the process of medical abortion and observe the changes of thyroid hormone during abortion.Methods:A total of 60 female Institute of Cancer Research (ICR) mice aged 6-8 weeks were divided into control group,control group with 0 mgRU486 group (control-0 mgRU486),control group with 2 mgRU486 group (control-2 mgRU486),hyperthyroid pregnant mice with 0 mgRU486 group (hyper-0 mgRU486),hyperthyroid pregnant mice with 2 mgRU486 group (hyper-2 mgRU486),and hyperthyroid pregnant mice with 20 mgRU486 group (hyper-20 mgRU486).In the hyperthyroidism groups,L-thyroxine sodium was intraperitoneally injected every day at 30 μg·kg-1·day-1 until the end of the experiment.On the 7th day of the experiment,free triiodothyronine (FT3),free tetraiodothyroxine (FT4),thyroxine (TT4),and thyroid-stimulating hormone (TSH) levels were tested.The mice in the control groups and those in the experimental groups were paired with the male mice (2:1) on the 10th day of the experiment,and the caging was recorded.On the 8th day of pregnancy (day 8),pregnant mice were subcutaneously injected with mifepristone in different doses and were sacrificed 6 h later.Pregnancy rate and the number of embryos were recorded.Thyroid tissues were observed by hematoxylin and eosin (HE) staining.Serum TSH level was determined by radioimmunoassay.Results:Six hours after injection with mifepristone,serum FT3,FT4,and TT4 levels of pregnant mice were all increased.The increased levels in the mice under hyperthyroidism were different from those in the control groups (P ＜ 0.05).There was no difference in the embryo number and pregnancy rate between the experimental and the control groups;HE staining indicated that there was no significant change in microscopic features before and after mifepristone administration.Conclusion:Serum thyroid hormone level of mice under hyperthyroidism was significantly increased after mifepristone administration.Therefore,mifepristone should be avoided when hyperthyroidism has not been controlled.
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