| Objective The thyroid physiology of preterm infants is different from that of full-term infants,and the physiological fluctuation range and time of thyroid hormone level of preterm infants in different gestational ages are also different.At the same time,some studies at home and abroad have found that birth weight,gender,mode of delivery and twin factors also have impacts on the thyroid function of preterm infants,however,there is no comprehensive analysis of relevant clinical cases to explore it.The purpose of this study is to detect the thyroid hormone level of preterm infants 14 days after birth,in order to explore the influencing factors of thyroid function of preterm infants,and establish the reference value ranges of thyroid function suitable for preterm infants in our hospital.Methods We selected 514 preterm infants who met the inclusion criteria in our hospital from January 01,2019 to December 31,2021 as our research objects.They were divided into groups according to gestational age,birth weight,gender,mode of delivery,and singleton and twin factors.Their venous blood was taken and their thyroid function 14 days after birth was detected by chemiluminescence immunoassay.Mann Whitney U test or Kruskal Wallis h test were used to compare thyroid hormone levels between groups,and 95% confidence interval was calculated to explore the reference value ranges of thyroid function in gestational age-related preterm infants.Spearman correlation analysis was used to study the correlation between gestational age and birth weight and the levels of FT3,FT4 and TSH.The influencing factors of thyroid hormone level were analyzed by full entry multiple linear regression to clarify the effects of gestational age,birth weight,gender,mode of delivery and singleton and twin factors on thyroid function of preterm infants.Results 1.Gestational age was positively correlated with FT3 with the correlation coefficient of 0.543,and was positive correlation with FT4,with the correlation coefficient of0.358,and was negatively correlated with TSH with the correlation coefficient of-0.200,P value less than 0.01.2.The reference value ranges of thyroid function indexes FT3,FT4 and TSH of premature infants based on gestational age respectively are:(1.53-3.72)pg/ml,(0.81-1.91)ng/dl and(1.32-7.80)μIU/ml for early premature infants;(1.74-4.16)pg/ml,(0.90-2.82)ng/dl,(0.63-7.64)μIU/ml for middle premature infants;(2.07-4.88)pg/ml,(1.09-2.27)ng/dl,and(1.14-7.06)μIU/ml for late premature infants.3.Birth weight was positively correlated with FT3 with the correlation coefficient of 0.516,and was positive correlation with FT4 with the correlation coefficient of 0.392,and was negative correlation with TSH with the correlation coefficient of-0.209,P value less than 0.01.4.The reference value ranges of thyroid function indexes FT3,FT4 and TSH of preterm infants based on birth weight respectively are:(1.53-4.06)pg/ml,(0.81-1.83)ng/dl and(1.14-7.84)μIU/ml for premature infants with BW<1500g;(1.67-3.98)pg/ml,(0.88-2.97)ng/dl,(0.94-7.64)μIU/ml for premature infants with 1500 g ≤ BW<2000g;(1.91-4.75)pg/ml,(1.09-2.31)ng/dl,and(1.14-6.32)μIU/ml for premature infants with BW≥2000g.5.FT3,FT4 and TSH were lower female than in male,P value greater than 0.05.6.FT3 in premature infants born via normal spontaneous vaginal was higher than that born via cesarean section.FT4 in premature infants born via normal spontaneous vaginal was lower than that born via cesarean section,and TSH in premature infants born via normal spontaneous vaginal was higher than that born via cesarean section,P value greater than 0.05.7.FT3 was higher in singleton preterm infants than in twin preterm infants,FT4 was lower in singleton preterm infants than in twin preterm infants,and TSH was higher in singleton preterm infants than in twin preterm infants,P value greater than 0.05.8.The results of multiple linear regression analysis showed that when FT3 was the dependent variable,gestational age,birth weight were statistically significant(P <0.05),when FT4 was the dependent variable,gestational age was statistically significant(P <0.05),and when TSH was the dependent variable,birth weight was statistically significant(P< 0.05).Conclusion1.FT3 and FT4 at 14 days after preterm birth are positively associated with gestational age,and TSH levels were negatively correlated with gestational age.So a gestational age-based thyroid function reference value ranges for preterm infants need to be established.2.The thyroid function of preterm infants on the 14 th day after birth is correlated with birth weight,FT3 and FT4 are positively correlated and TSH is negatively correlated,so the reference value ranges of premature thyroid function based on birth weight should be formulated.3.Gestational age,birth weight are the influencing factors of FT3 level of preterm infants 14 days after birth.Gestational age is the influencing factors of FT4 level,and birth weight is the influencing factor of TSH level. |
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