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ORIGINAL ARTICLE
Year : 2019  |  Volume : 3  |  Issue : 1  |  Page : 30-35

Safety of mifepristone in medical abortion in hyperthyroidism pregnant mice


Department of Family Planning, Obstetrics and Gynecology Hospital of Fudan University, Shanghai 200011, China

Date of Submission09-Jan-2019
Date of Web Publication11-Apr-2019

Correspondence Address:
Xiao-Ying Yao
Department of Family Planning, Obstetrics and Gynecology Hospital of Fudan University, No. 419, Fangxie Road, Shanghai 200011
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2096-2924.255990

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  Abstract 


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.

Keywords: Hyperthyroidism; Medical Abortion; Mifepristone; Pregnant Mice


How to cite this article:
Tang YH, Yao XY. Safety of mifepristone in medical abortion in hyperthyroidism pregnant mice. Reprod Dev Med 2019;3:30-5

How to cite this URL:
Tang YH, Yao XY. Safety of mifepristone in medical abortion in hyperthyroidism pregnant mice. Reprod Dev Med [serial online] 2019 [cited 2019 Apr 24];3:30-5. Available from: http://www.repdevmed.org/text.asp?2019/3/1/30/255990




  Introduction Top


Thyroid diseases are the most common endocrine diseases except for diabetes in women in gestation period. The incidence of pregnancy combined with hyperthyroidism has been reported to be about 1‰–2‰.[1] As an antiprogestogen drug, mifepristone possesses the effects of anti-luteum, anti-implantation, anti-ovulation, and induction of menstruation, which is always the first-line treatment for medical abortion.[2] However, for pregnant women with abnormal thyroid function, there is still no unified agreement on how and when to use mifepristone.[3] The safety of mifepristone in hyperthyroidism patients is still controversial.[4],[5],[6] In this study, the influence of mifepristone on thyroid function was investigated using a hyperthyroidism animal model, and the drug safety was observed under hyperthyroidism status, which provided experimental basis for clinical medication.


  Methods Top


Equipment

Mouse metabolic cage (TECNIPLAST, USA), electronic analytical balance, desk centrifuge (DD-5M, Xiangyi, China).

Reagents

L-thyroxine sodium was provided by Dalian Meilun Biotechnology, Co., Ltd., China. Mifepristone was purchased from (Sigma-Aldrich, USA). Free triiodothyronine (FT3), free tetraiodothyroxine (FT4), thyroxine (TT4), and thyroid-stimulating hormone (TSH) radioimmunoassay kits were provided by R&D Systems (USA).

Animals

A total of 60 female inbred strain mice aged 6–8 weeks were provided by JieSijie Experimental Animal Co., Ltd., Shanghai, China, and raised in an animal house in the Obstetrics and Gynecology Hospital of Fudan University. The mice were raised in a stable environment at 20°C ± 2°C, relative humidity 36% ± 2%, and light/dark cycle 12 h/12 h. All the cages, food, and water were sterilized by autoclaving. The mice were allowed with free access to water and food and were fed with complete nutrient pellet feed. Those in the metabolic cage were fed with powder feed milled from the regular one. Thirty male Institute of Cancer Research (ICR) mice of the same age were used.


  Experimental Methods Top


Methods

A total of 60 female ICR mice aged 6–8 weeks were randomly 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. The mice in the control groups were intraperitoneally injected with phosphate-buffered saline of equivalent dose until the end. On the 7th day of the experiment, blood from caudal vein was collected to test FT3, FT4, TT4, and TSH levels. The metabolism in the metabolic cage was observed and recorded. The mice in the control groups and hyperthyroid groups were paired with male mice (2:1) on the 10th day of the experiment, and the caging was recorded. On the 2nd day of caging, day 0 of pregnancy was recorded if vaginal plug was found, and the days of pregnancy were calculated accordingly. On the 8th day of pregnancy (day 8), pregnant mice were subcutaneously injected with mifepristone of different doses and were sacrificed 6 h later. The thyroid and liver were taken out to observe and weigh, and organ coefficient was calculated. Pregnancy rate and the number of embryos were recorded. Thyroid tissues were stained with hematoxylin and eosin (HE) [Figure 1].
Figure 1: Schematic illustration of the experiment. Sixty female ICR mice were divided into six groups. L-thyroxine sodium was intraperitoneally injected every day at 30 μg·kg−1·day−1 in the hyperthyroidism groups. On the 7th –9th day of the experiment, FT3, FT4, TT4, and TSH levels were tested, and the mice were kept in the metabolic cage to observe metabolism. At the end of the experiment, the thyroids and livers of the mice were taken out to observe and weigh. FT3: Free triiodothyronine; FT4: Free tetraiodothyroxine; TT4: Thyroxine; TSH: Thyroid-stimulating hormone.

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Measurement for free triiodothyronine, free tetraiodothyroxine, thyroxine, and thyroid-stimulating hormone

The serum levels of FT3, FT4, TT4, and TSH were measured by radioimmunoassay.

Statistical method

SPSS version 22.0 (SPSS Inc., Chicago, IL, USA) software was used to analyze the data. The data were expressed as mean ± standard deviation (SD). Comparison between the groups was analyzed by one-way analysis of variance. Multiple comparisons were analyzed by least significant difference method if homogeneity of variance was true. P < 0.05 was considered statistically significant.

Flowchart

The experimental design is shown in [Figure 1]; 60 female ICR mice were divided into six groups. L-thyroxine sodium was intraperitoneally injected every day at 30 μg·kg−1·day−1 in the hyperthyroidism groups. On the 7th day of the experiment, FT3, FT4, TT4, and TSH levels were tested, and the mice were kept in the metabolic cage to observe metabolism. At the end of the experiment, the thyroids and livers of the mice were taken out to observe and weigh.


  Results Top


Molding

General condition

The mice in the control groups were in good status, showing sensitive reaction and glossy fur. Those in the experimental groups were in hyperactive and irritated status, and some had dehairing. No death occurred during experiment.

Changes of serum free triiodothyronine, free tetraiodothyroxine, thyroxine, and thyroid-stimulating hormone levels

On the 7th day of the experiment, serum FT3, FT4, TT4, and TSH levels were measured via blood collection from caudal vein. The mean ± SD of FT4 and TT4 of the control groups was taken as normal range. The results were judged as positive if the serum value was beyond the range. The comparisons in FT3, FT4, TT4, and TSH levels between the experimental groups and the control groups are shown in [Table 1].
Table 1: Thyroid hormone levels on the 7th day of modeling

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On the 7th day of the experiment, serum FT4 and TT4 levels were significantly elevated (P < 0.05), meeting the requirement of modeling.

Results in metabolic cage

On the 7th –9th day of the experiment, the mice from each group were placed in the metabolic cage for 24 h to observe water intake, food intake, urine volume, and fecal output. Water intake and urine volume had significant differences between the experimental and control groups (P < 0.05) [Table 2].
Table 2: Basic metabolism condition of mice

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The mice in the experimental group were in hyperactive and irritated status, with increase in water intake and urine volume. The basic metabolism had a significant difference compared with the control group. Meanwhile, serum TT4 and FT4 levels were significantly increased (P < 0.05), and TSH level was significantly reduced (P < 0.05), indicating successful hyperthyroidism model in mouse.

Pairing condition

A total of 45 pregnant mice were obtained at the end of the experiment (n = 20 in the control group, 100%; n = 25 in the experimental group, 83.3%). The pregnancy rate and blank pregnancy rate had no statistical significance between the groups [Table 3].
Table 3: Pairing condition of each group

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Comparison in pregnancy of each group

After sacrifice, the number of embryo sac was recorded. No significant difference was observed between the experimental and control groups. As illustrated in [Figure 2], although embryo sac resorption was observed in the hyperthyroidism groups, there was no statistical difference [Table 4].
Figure 2: Uterus and embryo sac condition in the pregnant mice. (a) Uterus in the control group: embryo sac is orderly arranged with consistent size, and no avascular necrosis or uterine contracture is observed. (b) Uterus in the hyper-20 mgRU486 group: embryo sac size is different from embryo damage signs (arrow), and uterine contracture is associated with ischemia.

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Table 4: Pregnancy statistics of mice

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Comparison in thyroid and liver organ coefficients between groups

The result of comparison in thyroid and liver organ coefficients of the experimental groups is shown as follows. The two coefficients in the experimental groups had a significant difference compared with the control groups (P < 0.05), as shown in [Table 5].
Table 5: Thyroid and liver organ coefficients in the experimental group (mean ± SD)

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Comparison in thyroid hormone level before and 6 h after mifepristone administration

On the 8th day of pregnancy, before and after 6 h of mifepristone administration, serum FT4, FT3, TT4, and TSH levels of each group were measured. The comparisons in the FT3, FT4, TT4, and TSH levels between the groups are shown in [Table 6].
Table 6: Thyroid hormone levels at different times

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Serum FT3, FT4, and TT4 levels were increased in different degrees in the pregnant mice before and after 6 h of mifepristone administration. The increased levels in the experimental groups had a significant difference compared with those in the control groups (P < 0.05), indicating that mifepristone could induce sudden rise in thyroid function. Before and after mifepristone administration, the TT4 level in the normal pregnant mice also had a significant change (P < 0.05).

Morphology comparison in thyroid tissues

As shown in [Figure 3], after sacrifice, there is a significant difference in morphology between the control group and the experimental group. The thyroid volume in the experimental group is significantly enlarged, accompanied with tissue hyperemia.
Figure 3: Morphology comparison in thyroid tissues. Left: Thyroid in the control group; Right: Thyroid in the experimental group.

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Hematoxylin and eosin staining in thyroid tissues

At the end of the experiment, the mice were sacrificed to perform HE staining on thyroid tissues. As illustrated in [Figure 4], the thyroid tissues in the control group, control-0 mgRU486 group, and control-2 mgRU486 group are composed of follicles with different sizes in roundness or ellipse shape. The follicular wall is composed of single-layer epithelial cells, and follicular cavity is fulfilled with gelatine. The follicular cavity is smooth, full of deep red and homogeneous gelatine. Significantly enlarged follicles can be observed in the hyper-0 mgRU486 group, hyper-2 mgRU486 group, and hyper-20 mgRU486 group. The follicular epithelial cells are in cube with enlarged nucleus, and no papillary hyperplasia is observed. There is no significant difference between the groups. Thus, compared with the control groups, hyperthyroidism features are observed in the experimental groups. The comparison between control-0 mgRU486 and control-2 mgRU486 groups indicates that mifepristone administration cannot cause a significant histological change. Compared with hyper-2 mgRU486 and hyper-20 mgRU486 groups, the mice under hyperthyroidism with short-term mifepristone administration in d group do not show a significant pathological change. The comparison between hyper-2 mgRU486 and hyper-20 mgRU486 groups demonstrates that mifepristone with different doses has no significant histological difference in the mice under hyperthyroidism.
Figure 4: HE staining changes of thyroid tissues (×2 amplification). (a) control; (b) control-0 mgRU486; (c) control-2 mgRU486; (d) hyper-0 mgRU486; (e) hyper-2 mgRU486; (f) hyper-20 mgRU486.

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  Discussion Top


Effect of pregnancy on thyroid axis

It has been found that the changing trend of TSH in the early pregnancy is consistent with hCG in a mirror manner.[7] hCG and TSH have homology in molecular structure, which is the basis for the cross-reaction between them.[8],[9],[10],[11] The hCG level is higher, the TSH level is lower, and the symptoms are more significant, indicating a negative correlation between these two hormones. It suggests that HCG has an important role in regulating the pituitary–thyroid axis, which is also known as hCG-mediated transient TSH suppression.

In our study, we found that TT4 level in the control-0 mgRU486 group was significantly increased (P < 0.05), which indicated the existence of physiological hyperthyroidism under pregnancy status.

Influence of hyperthyroidism on pregnancy rate

Hyperthyroidism, an endocrine disease, is common in women. The poor outcomes of women of childbearing age combined with hyperthyroidism include decreased fertility capability, abortion, premature, stillbirth, and low-birth-weight babies.[12],[13] The abortion rate of hyperthyroidism pregnancy is high up to 26%, and the premature rate is 15%. In 1991, Easterling et al.[14] investigated six pregnant women with hyperthyroidism. The hemodynamic changes of the patients were monitored from the 12th week of pregnancy. It was found that cardiac output was increased by 65%, total peripheral resistance was decreased by 35%, and heart rate was increased by 21%. Thus, the great change of hemodynamics in the hyperthyroidism pregnant woman cannot be ignored. Even if thyroid function is corrected and maintained to normal, the hemodynamic change will continue for a while. Thus, the pregnancy rate and abortion rate of hyperthyroidism are worth attention.

In our study, the embryonic number in the hyperthyroidism pregnant mice had no statistical significance compared with that in the normal group. Although embryo resorption was observed, no statistical significance was found (P > 0.05), which might be related with the light hyperthyroidism degree in our modeling.

Influence of mifepristone on hormone levels in hyperthyroidism pregnant mice

In the US and Western Europe, mifepristone combined with misoprostol has always been the first-line treatment for medical abortion.[15] In the clinic, for the hyperthyroidism patients, because mifepristone can aggravate hyperthyroidism and induce hyperthyroidism crisis,[16] clinicians do not choose medical abortion that is a relatively mature and less-invasion treatment. The safety of mifepristone in hyperthyroidism status has always received attention in the clinic.

Our results indicated that under pregnancy status, after 6 h of mifepristone administration, serum FT3, FT4, and TT4 levels were elevated in different degrees. The elevated levels in the mice under hyperthyroidism had a significant difference compared with the control group (P < 0.05). Low- and high-dose mifepristone could induce sudden rise of thyroid function. The TT4 level before and after mifepristone administration in the normal mice also had a significant difference (P < 0.05), proving the synergistic effect of mifepristone on thyroid axis. Mifepristone is not recommended under the condition that hyperthyroidism is not controlled.

Thus, we believe that thyroid function examination is required before pregnancy. The patients not pregnant should delay the pregnancy using contraception until thyroid function is controlled. For the pregnant woman with hyperthyroidism, the disease should be actively controlled. In the hyperthyroidism period, mifepristone is not appropriate for medical abortion. The patients with hyperthyroidism could use it under the condition that thyroid function is in the normal level.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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2.
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Laurberg P, Bournaud C, Karmisholt J, Orgiazzi J. Management of Graves' hyperthyroidism in pregnancy: Focus on both maternal and foetal thyroid function, and caution against surgical thyroidectomy in pregnancy. Eur J Endocrinol 2009;160:1-8. doi: 10.1530/EJE-08-0663.  Back to cited text no. 12
    
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Easterling TR, Benedetti TJ, Schmucker BC, Carlson K, Millard SP. Maternal hemodynamics and aortic diameter in normal and hypertensive pregnancies. Obstet Gynecol 1991;78:1073-7.  Back to cited text no. 14
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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