The Incidence Of Transient Hypothyroxinemia In Premature Infants And Its Clinical Observation

The premature infant is a special crowd, because thehypothalamic-pituitary-thyroid axis is still immature, the iodothyronines whichcontrol thyroid hormone metabolism is immature and the thyroid-binding globulin isrelatively insufficient, it is tend to be the transient hypothyroxinemia after birth(transient hypothyroxinemia of prematurity, THOP). Its characteristics are low of T4level in serum but the level of TSH is normal, the most usually recovers in fewmonths. The more immature, the higher of THOP incidence. This investigation was tofind out THOP incidence, analyze the high-risk factors of THOP and observe thequantity of infant early life by measuring serum T4 and TSH which is taken from theheel blood on 3-5 days after birth. The premature infants who were less than 32weeks gestational ages and THOP affected will be enrolled the thyroid hormonetreatment random-control trial, observe the effect of its living quantity.Topic 1 The THOP incidence and it's high-risk factorsMethod: Measure serum T4 and TSH level in 208 premature infants which was takenfrom the heel blood on 3-5 days after birth by Time-resolved FluorescenceImmunoassay method, calculated the incidence of THOP, analyzed its high-riskfactors.Result:1. The incidence of THOP was related to gestational ages and birth weights. T4＜77n mol/L, TSH＜20 m U/ L was defined as THOP. According to observationbetween different gestational age groups, the incidence of THOP was significantlydifference. The incidence of THOP which gestational ages≤32 w was higherthan＞32 w～group and≥37 w group, but there was no difference between＞ 32 w～group and≥37 w. According to observation between different birthweight groups, the incidence of THOP was significantly difference. The incidence ofTHOP which birth weight≤1500 g was higher than birth weight 1501-2499 ggroup and≥2500 g group, also there was significantly difference between 1501-2499 g group and≥2500 g group.2. The incidence of THOP was related to mother and newborn diseases. In motherdiseases, intrapartum infection was the high-risk factor of THOP, butpregnancy-induced hypertension decreased the incidence of THOP. In newborndiseases, polycythemia, respiratory distress syndrome and septicemia were all thehigh-risk factors of THOP.3. Multiple Logistics regress analyzed the high-risk factors of THOP. Birth weight,respiratory distress.syndrome, polycythemia, and mother pregnancy-inducedhypertension into the equation.Conclusion: The incidence of THOP of the premature and low-birth-weight infantswhose gestational age≤32 w or birth weight≤1500 g was 64% and 80%respectively. The low birth weight, respiratory distress syndrome and polycythemiawere the high-risk factors of THOP. Pregnancy-induced hypertension decreased theincidence of THOP.Topic 2 Clinical observations of THOP in the infants who were≤32 w or≤1500 g during infant's early life.Method: Measured serum T4 and TSH level in 72 premature or low-birth-weightinfants who were≤32 w or≤1500 g and without L-thyroxine treatment takenfrom the heel blood on 3-5 days after birth by Time-resolved FluorescenceImmunoassay method. Compared with the incidence of perinatal diseases, livingquantity and weight gain between the THOP group and control group.Result:1. Compared with the incidence of perinatal diseases between the THOP group andcontrol group. T4＜77 n mol/L and TSH＜20 m U/L was defined as THOP. In thisstudy, there were 49 infants in the THOP group and 23 infants in control group. The incidence of asphyxia, intracranial hemorrhage, apnea, respiratory distress syndrome,bronchopulmonary dysplasia, polycythemia, hypocalcemia, hypoglycemia,septicemia, patent ductus arteriosus, cardiac dysfunction and abnormality were nodifferences between the THOP group and control group.2. Observation of living quantity after birth between the THOP group and controlgroup. In the THOP group, the days of oxygen supplement and mechanicalventilation were increased, the days of passing stool regularly were delayed, the daysof hyperbilirubinemia were extended, the days of recovering to birth weight andcalories taken to 100 kCal/(kg .d) were extended. The days of attaining to hospitaldischarge weight and the hospitalization days were prolonged, those were allsignificantly differences. The infant's weight gain after recovering to birth weightwas no difference between the THOP group and control group.Conclusion: THOP was not related to morbidities in the infants who were≤32wor≤1500g during neonatal early period. But it lowered living quantity after birth.Topic 3 The effect of treatment of THOP to morbidity and living quantity duringinfant's early life.Method: Measured serum T4 and TSH level in premature or very-low-birth-weightinfants who were≤32w or≤1500g taken from the heel blood on 3-5 days afterbirth by Time-resolved Fluorescence Immunoassay method. Divided the THOP group68 infants randomly to two subgroups, one was L-T4 treatment group and anotherwas control group. The L-T4 treatment group supplied L-thyroxine 8μg/kg. d on 5-7days after birth for 4-6 weeks. Compared with morbidity and living quantity andweight gain during the infant's early life between the L-T4 treatment group andcontrol group.Result:1. Compared with morbidity of neonatal diseases between the L-T4 treatment groupand control group. In this study, the incidence of intraventricular hemorrhage, apnea,bronchopulmonary dysplasia, hypoglycemia, septicemia, patent ductus arteriosus andcardiac dysfunction were no differences between the L-T4 treatment group and control group. The incidence of hypocalcemia was higher in the L-T4 treatment groupthan control group, there was difference by chi-square test.2. Observation of living quantity during infant's early life between the L-T4 treatmentgroup and control group. The days of oxygen supplement and mechanical ventilation,passing stool regularly, hyperbilirubinemia, recovering to birth weight and caloriestaken to 100 kCal/(kg .d), attaining to hospital discharge weight and thehospitalization days were no differences between the L-T4 treatment group andcontrol group. The weight gain after recovering to birth weight was increased in theL-T4 treatment group than control group, there was difference between two groups.Conclusion: L-thyroxine supplement to the THOP infants could not obviouslyimprove living quantity of the THOP during infant's early life. But the incidence ofhypocalcemia was higher in the L-T4 treatment group than control group. It isnecessary to enlarge sample trials in further study for benefits of thyroid hormonesgiven to very preterm infants in the neonatal period.