Effects Of Different Plasma Glucose Levels On Thyroid Function

Objective To investigate the effects of different plasma glucose levels and the course of diabetes on serum thyroid hormone levels,whether the thyroid antibodies are positive or not,and the incidence of thyroid dysfunction.Methods A total of 1028 outpatients and inpatients were selected,admitted to People's Hospital of Liaoning Province during the period of February 2018 to April 2019,including those with normal plasma glucose and those with abnormal plasma glucose.All the selected subjects were excluded from acute complications of diabetes,recent aggravation of chronic complications of diabetes,thyroid diseases,pituitary and hypothalamic diseases affecting thyroid function and other endocrine diseases.Low T₃syndrome was excluded.No previous history of using drugs affecting thyroid function,serious infection,malnutrition or stress trauma,malignant tumor,organic heart disease or arrhythmia,and no major surgery in the past six months.Subjects were excluded who accompanying hepatic insufficiency?the levels of AST and ALT are more than 2 times of normal value?,renal insufficiency?creatinine level is more than the upper limit of the normal value?,pregnancy and lactating patients.The basic information of allergy history,family history,disease history?including whether diabetes is diagnosed and its type,the course of the disease,and combined chronic complications?were recorded.Blood samples were taken in the morning of the next day after fasting for more than 8hours to detect fasting venous plasma glucose?FPG?,glycated hemoglobin?Hb A1c?,serum free triiodothyronine?FT₃?,serum free thyroid hormone?FT₄?,and thyroid stimulating hormones?TSH?,thyroid peroxidase antibody?TPOAb?,thyroglobulin antibody?TgAb?and uric acid?UA?.Two hours later,blood samples were taken to detect postprandial plasma glucose?PPG?.The results of thyroid ultrasound were also recorded.All the selected subjects were divided into three groups according to Hb A1c:Group I?Hb A1c<6.5%?,Group II?6.5%?Hb A1c<9%?,and Group III?Hb A1c?9%?.The influence of different Hb A1c levels on thyroid related indexes and the possible related factors were analyzed.Results?1?All the subjects were divided into DM-free group,<10-years group and?10-years group according to the course of diabetes.The level of FT3 in DM free group was higher than that in<10-years group and?10-years group?P=0.043 and 0.018,respectively?.The TSH level in the<10-years group was lower than that in the?10-years group?P=0.037?.There was no significant difference in FT₄level among the three groups?P>0.05?;?2?The higher the Hb A1c,the lower the FT₃and the higher the FT₄.TSH in group III was higher than that in group II.There were 73 patients with abnormal thyroid function among all the subjects,accounting for 7.36%of the total.Of which the highest prevalence was subclinical hypothyroidism?3.83%?,followed by subclinical hyperthyroidism?2.42%?,hypothyroidism?0.81%?,and hyperthyroidism?0.30%?.There was a statistically significant difference in the prevalence of thyroid dysfunction among Hb A1c group I,II,and III?FISHER=29.018,P=0.000?.The prevalence of thyroid dysfunction in group I,II,and III was 0.50%,7.00%,and 11.90%,respectively.The highest prevalence among the three groups was all hypoparathyroidism.The higher the level of Hb A1c,the higher the prevalence of thyroid dysfunction.There was no significant difference in whether the thyroid antibodies were positive or not and the prevalence of thyroid nodules among the three groups?P>0.05?;?3?In the linear regression model,there was a negative correlation between serum FT₃and Hb A1c??=-0.150,P=0.006?.There was no significant difference between FPG,PPG and thyroid hormones?P>0.05?;?4?The course of diabetes was an independent risk factor for TgAb?OR=1.847,95%CI:1.211-2.815,P=0.000?.There was no statistical significance between the positive prevalence of TPOAb and the course of diabetes?P>0.05?;?5?The serum FT₃level?2.92±0.37 pg/m L?in women was lower than that in men?3.27±0.98 pg/m L?,with a statistically significant difference?t'=3.37,P=0.001?.The serum TSH level?2.47±1.83 m U/L?was higher in women than that in men?2.03±1.43 m U/L?,with a statistically significant difference?t=-2.56,P=0.01?.There was no significant difference in serum FT₄levels between men and women?P>0.05?;?6?There was no statistical significance between blood uric acid levels and the prevalence of thyroid dysfunction?P>0.05?.Conclusion The level of serum FT₃decreases with the increase of Hb A1c level.The prevalence of thyroid dysfunction is related to the level of Hb A1c,whether there is diabetes and the course of it.The higher the level of Hb A1c and the longer the course of diabetes,the higher the prevalence of thyroid dysfunction,of which the incidence of subclinical hypothyroidism is the highest.The course of DM is an independent risk factor for TgAb.