Effect of iodine on the pathogenesis of postpartum thyroiditis / 中国地方病学杂志

ABSTRACT

Objective To explore the effect of iodine on the pathogenesis of postpartum thymiditis.Methods Forty-four female C57BL/6J mice,8-week old,fed by low iodine dietary(the concentration of iodine≤35 μg/kg),were randomly divided into 4 groupsnon-pregnancy experimental autoimmune thymiditis(non-pregnancy EAT)group with 8 mice,EAT of mice was induced by immunization with pig's thyroglobulin(Tg)in the presence of complete Freund's adjuvant.Six mice in non-pregnancy EAT group survived at the end of experiment;normal iodine-PPT(NI-PPT)group,10-fold high iodine-PPT(10HI-PPT)group and 50-fold high iodine-PPT(50HI-PPT)group with 12 mice in each group.The last 3 groups mice,who received the same immunization schedule as the above,were mated with adult male mice followed by induction of EAT.In the end,7,6 and 6 mice were noticed to be pregnant in each group.All animals were killed 4 weeks after postpartum.Histological severity of thyroid specimens was evaluated.The serum level of thyroglobulin antibody(Tg-Ab),thyroid pomxidase antibody(TPO-Ab),TT3 and TT4 were measured by radioimmunoassay(RIA).The expression level of IFN-γ/IL-4 mRNA in spleenwere assayed by RT-PCR.Results Pathological examination showed the infiltration of inflammatory cells.epithelial cell applanation,follicle atrophy or destruction.The severity of inflammation in non-pregnancy EAT bgroup.NI-PPT group and 10HI-PPT group was less serious than that in the 50HI-PPT group,the difference has bstatistical significance(P＜0.05).The level of TPO-Ab in non-pregnancy EAT group,NI-PPI-group,10HI-PPTgroup and 50HI-PPT group wag(14.32±8.85)%,(64.45±10.52)%,(38.46±5.57)%and(90.09±9.98)%.respectively the difference being statistically significant between any two groups(P＜0.05).There was no statisticaldifference(F＝0.484,P＞0.05)of Tg-Ab among non-pregnancy EAT group[(33.74±3.71)%],NI-PPT group [(29.65±2.06)%],10HI-PPT group[(37.21±3.87)%]and 50HI-PPT group[(33.87±4.17)%].There was no statistical difference(F＝1.596,P＞0.05)of TT3 among non-pregnancy EAT group (2.47±0.69)%,NI-PPT group(1.57±0.25)%,10HI-PPT group[(1.60±0.28)%]and 50HI-PPT group[(1.82±0.75)%].The level of TT4 in 50HI-PPT group[(66.68±5.47)%]was lower than that in non-pregnancy group,NI-PPT group and 10HI-PPTgroup[(99.87±5.97)%,(89.13±7.64)%and(91.05±5.82)%],the difference being statistically significant(P＜0.05).The expression level of IFN-γ mRNA was increasing,being 1.02±0.10,1.37±0.10,1.39±0.12 and 1.68±0.06 in non-pregnancy EAT group,NI-PPT group,10HI-PPT group and 50HI-PPT group.The difference had a statistical significance between any two groups except for NI-PPT group and 10HI-PPT group(P＜0.05).The expression level of IL-4 mRNA in 10HI-PPT group(0.49±0.04)and 50HI-PPT group(0.53±0.06)were all higher than non-pregnancy EAT group(0.24±0.05)and NI-PPT group(0.35±O.05),the differences being statistically significant (P＜0.05).Conclusions Adequate iodine supplementation during pregnancy and postpartum period is necessary,but iodine excess could induce postpartum thyroiditis.So iodine supplementation during pregnancy and postpartum should be adequate and reasonable.