Relationship Between Early Hypothyroidism And Thyroid Technetium Uptake Ratio In Patients With Graves Disease After ¹³¹I Treatment And Analysis Of Influencing Factors Of Early Hypothyroidism

Objective To investigate the relationship between thyroid technetium uptake ratio and early hypothyroidism in patients with Graves’Disease（GD）before and after ¹³¹I treatment,and to explore the main factors affecting early hypothyroidism in patients with Graves’disease.Methods A total of 202 patients with Graves’disease who received ¹³¹I therapy in the Department of Nuclear Medicine,the First Affiliated Hospital of Guangxi Medical University from January 2017 to May 2018 were included in the study,including 51 males and 151 females,aged from 16 to 77 years old,and with the median age of 38 years old.Relevant clinical data before treatment were recorded in detail,and the ^99mTc O₄^-uptake ratio（UR）,abbreviated as thyroid technetium uptake ratio,was calculated by static thyroid imaging before and three months after treatment.All patients were divided into early onset hypothyroidism group and non-early onset hypothyroidism group according to whether early onset hypothyroidism occurred.The clinical data and thyroid technetium uptake ratio before and after treatment in the two groups were compared.The patients with early-onset hypothyroidism were divided into hypothyroidism group and non-hypothyroidism group according to the thyroid technetium uptake ratio three months after treatment.The incidence of early-onset permanent hypothyroidism in the two groups was compared.The recorded clinical data were retrospectively analyzed,and the logistics regression model was established.The receiver operating characteristic（ROC）curve was drawn and the Area under the curve（AUC）of influencing factors was calculated to obtain the threshold.T test was used for comparison between measurement data groups with normal distribution,Mann-whitney U test for non-parametric distribution andχ² test for enumeration data.Differences with P<0.05 were statistically significant.Results（1）Basic characteristics:A total of 202 cases of Graves’hyperthyroidism were included,including 129 cases with early onset hypothyroidism,including 31 males and 98 females,with the median age of 38years old;There were 73 cases without premature hypothyroidism,including 20males and 53 females,with the median age of 36 years.（2）The thyroid technetium uptake ratios at 3 months after treatment between the early onset hypothyroidism group and the non-early onset hypothyroidism group were statistically significant（Z=-6.543,P<0.001）.Other clinical data such as gender,age,course of disease,Ati-thyroid Drugs,there were no significant differences between the two groups in ATD)treatment history,thyroid quality,¹³¹I dose,Free Triiodothyronine（FT₃）and Free Thyroxine（FT₄）（P>0.05）.（3）Three months after treatment,the incidence of early permanent hypothyroidism in the reduced-technetium uptake ratio group and non-reduced group was significantly different（χ²=5.849,P=0.016）.（4）According to the binary logistics regression analysis,the course of disease before treatment,the ratio of technetium taken and the ratio of technetium taken three months after treatment were related to the occurrence of early hypothyroidism,which were all included in the logistics regression model.The accuracy rate of prediction of early hypothyroidism by the model was 78.7%,the sensitivity and specificity of the model were 61.6%and 88.4%.Plotting the ROC curve resulted in a thyroid technetium uptake ratio AUC=0.544[95%CI:0.462–0.627,P=0.296]before treatment.Due to the small AUC of technetium uptake ratio before treatment,the median of 21.02 were considered as the critical values.The AUC of thyroid ^99mTc-technetium uptake ratio at 3 months post-treatment,AUC=0.777[95%confidence interval（CI）:0.709–0.846,P<0.001].The optimal critical value was 8.94,and the sensitivity and specificity were 58.9%and 88.4%,respectively.Conclusions Three months after ¹³¹I treatment,patients with thyroid technetium uptake ratio<8.94 are prone to premature hypothyroidism.Thyroid^99mTc O₄^-imaging at 3 months after ¹³¹I treatment is helpful for detecting early hypothyroidism and can provide guidance for judging whether early hypothyroidism will develop into permanent hypothyroidism.Patients with Graves’s Disease whose thyroid technetium uptake ratio>21.02 before ¹³¹I treatment should be alert to the occurrence of early hypothyroidism when formulating the ¹³¹I dose.