Study On The Correlation Between Thyroid Function And Disease Outcome In Premature Infants

Purposes:The thyroid function of hospitalized premature infants was monitored,and the relationship between thyroid function change and disease outcome was analyzed,so as to determine whether thyroid function change can be one of the indicators of disease outcome.Methods:1.From March 2018 to October 2019,a retrospective study was conducted on premature infants with a daily age ≤3 days and a hospitalization date ≥11 days.2.On the 7th and 14th day after birth,2 ml of blood was extracted in the morning,and the concentrations of free triiodogenic acid(FT3),free thyroxine(FT4)and thyrotropin(TSH)were detected by chemiluminescence analysis.According to birth gestational age(GA),it was divided into three groups:GA<28W,28W≤GA<34W,and 34W≤GA<37W.According to birth weight(BW),BW<1500g,1500g≤BW<2000g and BW≤2000g were divided into three groups.The correlation between thyroid hormone concentration at 7 and 14 days after birth and gestational age and birth weight was analyzed.The values of 17 perinatal high risk factors were assigned,and the relationship between multivariate linear regression analysis and thyroid hormone,and multivariate Logistic regression analysis and low T3 syndrome were evaluated.3.The clinical status of premature infants was rated by trained attending physicians on the day the blood was drawn according to the NCIS criteria.Those who were rated as critical on day 7 and 14 were included in the critical group;those who were rated as critical on day 7 but rated as non-critical on day 14 were included in the transition group;those who were rated as non-critical on day 7 and 14 were the non-critical group(control group).The thyroid hormone concentrations at two time points were compared between the 3 groups.The differences in thyroid hormone concentrations at days 7 and 14 were calculated for AFT3,AFT4,and ATSH,and the values of AFT3,AFT4,and ATSH were compared among the three groups.The special curves of the concentration of FT3、FT4 on dan 7 and dan 14,ΔFT3 and ΔFT4 were analyzed.4.The general clinical data and medication of premature infants should be collected.Results:1.From March 2018 to October 2019,a total of 228 premature babies were finally included in the study,with an average gestational age of 33.46±2.31 weeks and an average birth weight of 2168±541.02 g,168 males and 60 females.2.With the increase of gestational age,the average concentration of FT3 and FT4 increased gradually on the 7th and 14th days after birth.On the 7th day,FT3 and FT4 concentrations were below the normal range;on the 14th day,FT3 concentrations of premature infants with GA≤32W were below the normal range,while FT4 concentrations of premature infants with GA≤33W were below the normal range.3.The changes in thyroid hormone concentration on days 7 and 14 showed that FT3 and F4 concentrations in the gestational age group 34≤GA<37W were higher than those in the other two groups,and those in the 28W≤GA<34W group were higher than those in the GA<28W group,which were positively correlated with gestational age and showed significant difference,while TSH showed no significant difference.The concentration of FT3 and FT4 in group 28W≤GA<34W and group 34<GA<37W increased on day 14 compared with that on day 7.FT3 and FT4 on days 7 and 14 were positively correlated with gestational age,while TSH was not correlated with gestational age.4.The concentration of FT3 in group BW<1500g on day 7 and 14 was lower than that in group 1500g≤BW<2000g,while that in group 1500g≤BW<2000g was lower than that in group BW≤2000g,showing a significant difference.There was no significant difference in FT4 concentration between groups with BW<1500g and 1500≤BW<2000g on day 14,but there was no significant difference between the two groups and groups with BW≥2000g on day 7.There was no difference in three TSH groups.The concentration of FT3 and FT4 in the three groups increased on day 14 compared with that on day 7,and the TSH concentration in the group with BW<1500g increased on day 14 compared with that on day 7,but there was no difference in the TSH concentration in the other two groups.FT3 and FT4 on days 7 and 14 were positively correlated with body weight,while TSH was negatively correlated with body weight.5.Multi-factor linear regression analysis after assigning values to 17 factors showed that 17 perinatal high-risk factors had no effect on FT3,FT4 and TSH.However,multiple Logistic regression analysis of low T3 syndrome showed that gestational age was the only high risk factor for premature infants with low T3 syndrome on days 7 and 14.6.The mean concentrations of FT3 and FT4 in the three groups on days 7 and 14 were all lower than the normal range,and the mean concentrations of FT3 and FT4 in critically ill patients were the lowest,showing differences.On the 7th day,there was no difference in TSH concentration among the three groups.On the 14th day,TSH concentration in the critical group was higher than that in the other two groups,showing differences.The mean TSH concentration on the 7th and 14th days was in the normal range.The FT3 concentration of the three groups increased on the 14th day compared with that on the 7th day.The concentration of FT4 in the critical group and the transition group increased on day 14 compared with day 7,but the concentration of FT4 in the non-critical group showed a decreasing trend,showing differences.TSH in the critically ill group increased from day 7 to day 14,but decreased in the other two groups,showing statistical differences.7.Three groups ΔFT3,ΔFT4 and ΔTSH showed that the critically ill groupΔFT3 was the lowest and had differences.ΔFT4 had no difference in the critical group and the transition group,but it was higher than that in the non-critical group.ΔTSH showed a progressive downward trend,and there was no difference.8.The concentration of FT3 and FT4 on the 7th day could assess the degree of disease severity,but FT4 was the most effective in the diagnosis of disease severity(AUC value was 0.726,95%CI value was 0.61-0.85).The cut value of FT3 on day 7 was 0.365pg/ml,the sensitivity was 71.8%,and the specificity was 64.7%.The FT4 cut value on day 7 was 0.428ng/dl,the sensitivity was 69.2%,and the specificity was 73.5%.Conclusions:1.The concentrations of FT3 and FT4 in premature infants after birth were positively correlated with gestational age and birth weight.The younger the gestational age,the smaller the birth weight,and the lower the concentrations of FT3 and FT4.2.Preterm birth is a high risk factor for low T3 syndrome.The more severe the degree of disease,the lower the concentration of FT3 and FT4,and vice versa.3.The concentration of FT3 and FT4 on the 7th day after birth could assess the degree of disease severity.The lower the concentration of FT4 on day 7,the more serious the disease.