The Occurrence Of Subclinical Thyroid Dysfunction In The Naval Officers And Soldiers And Research On Its Cognitive Impact

In recent years,the types and incidence of thyroid diseases have changed dramatically in China.Epidemiological data showed that the incidence of endemic goitre was significantly reduced,while the incidence of subclinical hypothyroidism(SCH)was increased.The importance given to the increasing number of SCH should be adjusted according to its degree of harm.In addition,more attention should be paid to thyroid health.However,the existence or severity of thyroid disease has not been reported.In addition,we concerned that patients with clinical hyperthyroidism or hypothyroidism are often accompanied by emotional and cognitive changes,However,the effect of subclinical thyroid dysfunction on cognitive ability is inconsistent.Therefore,it is necessary to evaluate thyroid function in different environments in the navy,the effects of subclinical thyroid dysfunction on stress ability and cognition were further studied by using animal models.Objective:In this study,we collected and analyzed the physical examination data of our hospital to evaluate thyroid function in different environments of the Navy.Established two mouse models of subclinical hyperthyroidism and subclinical hypothyroidism.Observe the changes in cognitive function and brain tissue in mice,and detect the concentrations of neurotransmitters.To clarify the impact of subclinical thyroid function level on cognitive ability,and provides a theoretical basis for clinical intervention.Methods:1.A retrospective analysis was made on the physical examination data of navy officers and soldiers who underwent physical examination in the physical examination center of ××hospital from June to September 2020.According to different stations,2198 cases were selected and divided into city group and ship group.The physical examination items included T3,T4,TSH,TPOAb,TGAb and thyroid ultrasound.2.According to the relevant literature,the preliminary experiment was conducted to explore and establish the required dose of subclinical thyroid function level mouse model,and the dose and time required for modeling were determined.According to the results of the preliminary experiment,30 BALB/C male mice,5-6 weeks,After a week of acclimatization,the Mice were randomly assigned to each group of ten,They were labeled as SHyper group,SCH group and control group.Mice in the SHyper group were intraperitoneally injected25μg/100 g of levothyroxine daily,and mice in the SCH group were intraperitoneally injected 1.5 mg/100 g of methimazole(MMI)daily.Mice in the control group were fed routinely.The responses of three groups of mice to external stimuli such as sound and light were observed.Three weeks later,Morris water maze test was conducted to compare and analyze the behavioral differences of the three groups of mice.At the same time,blood samples were collected and brain tissue samples of mice were cut on ice.Serum thyroid function,liver function and neurotransmitter levels in brain tissues were detected by ECLIA and ELISA.The brain tissue sections were stained with HE and Congo red,and observed the abnormality of neuronal cells and the distribution of Aβ in the brain of mice.Results:1.Survey results of subclinical thyroid dysfunction in navy under different environments: There were 1095 cases in the urban group,with an average age of34.00(29.00,41.00)years,663 cases in males and 432 cases in females,and 1103 cases in the ship group,with an average age of 33.00(28.00,38.00)years,1014 cases in males and 89 cases in females.There were differences in gender and age between the two groups(P<0.0001).In the urban group,111 cases(10.14%)had abnormal antibodies,9 cases(0.82%)had subclinical hyperthyroidism,85 cases(7.76%)had subclinical hypothyroidism,and 363cases(45.72%)had thyroid nodule.There were 84 cases of abnormal antibody(7.62%),5cases of subclinical hyperthyroidism(0.45%),38 cases of subclinical hypothyroidism(3.45%),and 258 cases of thyroid nodule(33.64%)in the ship group.Compared with the ship group,there is a higher probability of antibody abnormalities,subclinical hypothyroidism and thyroid nodules in the citygroup(P<0.05,P<0.001,P<0.0001).Multiple-factor analysis showed that the abnormal naval antibody was correlated with gender(P<0.0001).Subclinical hypothyroidism was correlated with group and antibody level(P=0.002,P<0.0001),The incidence of thyroid nodule was correlated with gender,age and elevated antibody levels(P<0.0001,P<0.0001,P=0.0003).2.Establishment of subclinical thyroid function mouse model: The serum TSH concentration of mice in SHyper group decreased(P<0.01),The serum concentrations of T3 and T4 in SHyper group were the same as those in control group(P>0.05).The serum TSH concentration of mice in SHyper group increased(P<0.01),with no significant difference in serum T3 and T4 concentrations(P>0.05).In addition,AST and ALT concentrations of mice in the two groups were at normal levels as indicators of liver function(P>0.05).3.The data of Morris water maze test: According to the performance of mice in navigation test,the escape latency was shortened in the SHyper group(P<0.05),there was no obvious abnormality in SCH group(P>0.05).Based on the performance of mice in space exploration test,the target quadrant distance ratio(%),target quadrant time ratio(%)and cross-platform times in SHyper group were significantly higher than those in control group(P<0.05).No difference was found in average velocity(P>0.05).And no difference was found in all evaluation indexes of the SCH group(P>0.05).4.Morphology and number of nerve cells in mouse brain: After HE staining,the granular cells in the DG area of the SHyper group mice aggregated,the cells were densely distributed,the frontal lobe did not change under the microscope.In the brain tissue slices of the SCH group,we found no significant changes.5.The distribution of Aβ in mouse brain: After Congo red staining,there was no abnormal deposition of Aβ in the hippocampus,frontal lobe and corpus callosum of the brain tissue samples of the three groups.6.The results of related neurotransmitter levels in mice: In the brain of SHyper mice,the concentration of monoamine neurotransmitters DA and 5-HT increased(P<0.01).And the same changes occurred in the cholinergic neurotransmitter Ach(P<0.05).And there was no meaningful changes in all evaluation indexes in SCH group(P>0.05).Conclusion:1.Naval officers and soldiers which stationed in coastal cities have a higher incidence of abnormal antibodies,subclinical hypothyroidism,and thyroid nodules,and it is necessary to pay more attention to them.For female naval officers and soldiers,more advanced prevention and control measures are needed,and female naval officers and soldiers with elevated autoantibodies need to further evaluate the benign and malignant nodules as they age.2.The mouse models of SHyper and SCH were successfully established by intraperitoneal injection of levothyroxine and methimazole.3.Mice in the SHyper group showed enhanced spatial learning and memory,and it was found that Increased neuronal cells in the DG area under the microscope,there was no abnormal deposition of Aβ in the brain,and We found that the concentrations of Ach,DA and 5-HT increased.It is suggested that in the state of SHyper,the increase in the number of neurons in DG region leads to the increase in the secretion of Ach,DA and 5-HT neurotransmitters,which leads to the enhancement of cognitive and memory function in mice.4.There was no significant difference in SCH group.It suggests that SCH would not cause cognitive decline in a short time.