早产儿生后14天甲状腺功能参考值范围及影响因素

Reference ranges and influencing factors of thyroid function in preterm infants at 14 d after birth

目的探索早产儿生后14 d甲状腺功能参考值范围及其影响因素。方法回顾性选取2019年1月1日至2021年12月31日在内蒙古医科大学附属医院住院的514例早产儿,并根据胎龄分为早期组(即26~31周+6)、中期组(32~33周+6)及晚期组(34~36周+6),分别为153例、129例及232例;或按出生体重分为<1500 g组(n=129)、≥1500~<2000 g组(n=120)、≥2000 g组(n=265)。所有患儿均生后14 d采集静脉血并经化学发光免疫法检测甲状腺功能,采用Mann-Whitney U检验或Kruskal-Wallis H检验比较不同胎龄及出生体重间游离三碘甲状腺原氨酸(free triiodothyronine,FT_(3))、游离甲状腺素(free thyroxine,FT_(4))、促甲状腺激素(thyroid stimulating hormone,TSH)水平差异,并计算95%参考值范围(P2.5为下限,P97.5为上限),采用Spearman相关分析进行胎龄和出生体重与FT_(3)、FT_(4)、TSH水平的相关性,以及多元线性回归分析甲状腺激素水平的影响因素。结果不同胎龄早产儿FT_(3)、FT_(4)、TSH的参考值范围:早期组早产儿分别为1.53~3.72 pg/ml、0.81~1.91 ng/dl、1.32~7.80μIU/ml,中期组为1.74~4.16 pg/ml、0.90~2.82 ng/dl、0.63~7.64μIU/ml,晚期组为2.07~4.88 pg/ml、1.09~2.27 ng/dl、1.14~7.06μIU/ml。不同出生体重早产儿的FT_(3)、FT_(4)、TSH参考值范围:<1500 g组早产儿为1.53~4.06 pg/ml、0.81~1.83 ng/dl、1.14~7.84μIU/ml,≥1500~<2000 g组为1.67~3.98 pg/ml、0.88~2.97 ng/dl、0.94~7.64μIU/ml,≥2000 g组为1.91~4.75 pg/ml、1.09~2.31 ng/dl、1.14~6.32μIU/ml。多元线性回归分析结果显示,FT_(3)与胎龄、出生体重呈正相关(β值分别为0.119和1.950×10^(-4)),FT_(4)与胎龄(β=0.031)呈正相关,TSH与出生体重(β=-4.250×10^(-4))呈负相关(P值均<0.05)。结论胎龄、出生体重为早产儿生后14 d甲状腺功能的影响因素;评价FT_(4)和TSH水平应分别参考基于胎龄和出生体重的甲状腺功能参考值范围。

Objective To investigate the reference ranges for thyroid function and its influencing factors in preterm infants at 14 d after birth.Methods This retrospective study involved 514 preterm infants who met the inclusion criteria in Affiliated Hospital of Inner Mongolia Medical University from January 1,2019 to December 31,2021.They were divided into three group according to their gestational age[early premature group(26-31+6 weeks,n=153),middle premature group(32-33+6 weeks,n=129)and late premature group(34-36+6 weeks,n=232)]or birth weight(BW)[<1500 g group(n=129),1500-2000 g group(n=120)and≥2000 g group(n=265)].Venous blood samples were collected from the infants at 14 d after birth and their thyroid function was determined by chemiluminescence immunoassay.The reference values of free triiodothyronine(FT_(3)),free thyroxine(FT_(4))and thyroid stimulating hormone(TSH)were calculated based on the values of 95%confidence intervals(CI)and expressed as percentiles in the range from P2.5 to P97.5.Mann-Whitney U test or Kruskal-Wallis H test was used to compare those thyroid hormone levels between groups.Spearman correlation analysis was used to study the correlation of gestational age or birth weight with FT_(3),FT_(4) and TSH levels.The factors influencing the levels of thyroid hormones were analyzed by multiple linear regression.Results The reference ranges for FT_(3),FT_(4) and TSH were 1.53-3.72 pg/ml,0.81-1.91 ng/dl and 1.32-7.80μIU/ml in the early premature infants,1.74-4.16 pg/ml,0.90-2.82 ng/dl and 0.63-7.64μIU/ml in middle prematures and 2.07-4.88 pg/ml,1.09-2.27 ng/dl and 1.14-7.06μIU/ml in late prematures.The reference ranges for the above three indexes were 1.53-4.06 pg/ml,0.81-1.83 ng/dl and 1.14-7.84μIU/ml in premature infants with BW<1500 g,1.67-3.98 pg/ml,0.88-2.97 ng/dl and 0.94-7.64μIU/ml in those whose BW between 1500 g and 2000 g and 1.91-4.75 pg/ml,1.09-2.31 ng/dl and 1.14-6.32μIU/ml in those whose BW≥2000 g.Multiple linear regression showed that the level of FT_(3) was positively correlated with gestational age(β=0.119,P<0.05)and birth weight(β=1.950×10^(-4),P<0.05);that of FT_(4) was positively correlated with gestational age only(β=0.031,P<0.05);and TSH level was negatively correlated with birth weight(β=-4.250×10^(-4),P<0.05).Conclusions Gestational age and birth weight are the factors influencing thyroid function in preterm infants at 14 d after birth.Evaluation of thyroid function with FT_(4) and TSH should based on the references ranges of different gestational age and birth weight.