Thyroid function in healthy premature infants.

Thyroid function was studied in healthy premature and term infants between 12 hours and 3 months of age. T4 and FT4I followed parallel courses in both groups; during the first 45 days, however, the values were significantly lower in premature infants under 34 weeks' EGA than in term infants (P less than 0.001). The post-delivery peak in TSH concentration (mean +/- SD) was 71.8 +/- 19.2 microunits/ml in the premature infants. In five premature infants, injection of TRH elicited a TSH increment of 29.4 +/- 20.7 microunits/ml at 30 minutes. T3 concentration was not significantly different in premature and term infants.     

Significance of transient postnatal hypothyroxinemia in premature infants with and without respiratory distress syndrome

The significance of relatively low thyroxine (T4) levels in preterm infants with and without respiratory distress syndrome (RDS) was assessed by evaluating the free T4 level, the thyrotropin (TSH) response to thyrotropin releasing hormone (TRH), and intellectual development in infants less than or equal to 35 weeks with cord blood T4 concentrations less than 6.5 microgram/100 ml. Fifty-four (19 well, 28 with RDS, and seven without RDS and sick) of 215 premature infants (25%) and 27 of 8,831 term infants (0.3%) had cord T4 levels less than 6.5 microgram/100 ml. Serum T4 levels were measured in 39 surviving preterm infants (20 RDS and 19 well) during the first 5 days of life and at 2, 4, 24, and 52 weeks postnatally. Serum total T4 level during the first week was 4.5 +/- 0.3 microgram/100 ml (mean +/- SEM). Free T4 levels ranged from 1.1 to 2.2 ng/100 ml (normal adult range 0.8 to 2.3 ng/100 ml). Administration of TRH resulted in a clear increase in both TSH and T4 levels in all infants. T4 levels increased significantly (r = .70, P less than .01) with increasing postnatal age, reaching stable levels by 6 to 7 weeks. Developmental quotients obtained in the infants with low T4 levels were no different from those found in a matched control population at 12 months of age. The low T4, free T4, and TSH concentrations and normal TSH responses to TRH found in these infants are characteristic of hypothalamic (tertiary) hypothyroidism, but differ from classic tertiary hypothyroidism in that the disorder was transient. The normal intellectual development at 12 months of age and the spontaneous increase in T4 levels that occurs over the first six weeks of life suggest that the low T4 levels in these infants reflect a benign relative delay in maturation of hypothalamic-pituitary-thyroid control.     

Serum thyrotrophin determination on day 5 of life as screening procedure for congenital hypothyroidism.

In 327 newborns cord blood thyroxine (T4) was 11.8 +/- 0.4 mug/100 ml (SEM) (151.9 +/- 5.1 nmol/l), and serum thyrotrophin (TSH) 6.7+/-1.0 muU/ml. Variability was marked for both T4 and TSH. Remeasured in the same patients on the fifth day of life, the TSH level was 3.7 +/- 1.0 muU/ml, lower than at birth (P less than 0.001), while scattering of TSH values was much smaller, with 99.4 % of values less than 12 muU/ml...     

Serum thyrotrophin determination on day 5 of life as screening procedure for congenital hypothyroidism

In 327 newborns cord blood thyroxine (T4) was 11.8 +/- 0.4 mug/100 ml (SEM) (151.9 +/- 5.1 nmol/l), and serum thyrotrophin (TSH) 6.7+/-1.0 muU/ml. Variability was marked for both T4 and TSH. Remeasured in the same patients on the fifth day of life, the TSH level was 3.7 +/- 1.0 muU/ml, lower than at birth (P less than 0.001), while scattering of TSH values was much smaller, with 99.4 % of values less than 12 muU/ml...     

Thyroid function in premature infants of different gestational age during the first month of life (author's transl)

To assess the function of the thyroid gland in premature infants of different gestational ages during the first month of life we determined simultaneously TSH, T4, T3, and rT3 serum concentrations in 116 preterm infants (gestational ages 31st to 38th week) during each of the first 30 days of life. The serum concentrations of TSH, T3, and rT3 changed significantly during this period. The TSH and rT3 values were highly increased on the first day and decreased thereafter. The T3 values, however, increased significantly during this period. During the first month of life the T4 values remained roughly unchanged independent of the age of the children. There was no significant influence on serum concentrations of thyroid hormones by gestational age. The 65 preterm infants with adaptational disorders showed no difference in their patterns of TSH and thyroid gland activity during the first month of life compared with 51 healthy premature infants. From the 4th to the 6h day of life -- a recommended period for the screening of congenital hypothyroidism -- the differences of TSH values measured were insignificant (16-18 muU/ml). The T4 values on these days remained all above 6.8 microgram/dl.     

Changes in serum concentrations of thyroid hormones and thyroid hormone-binding proteins during early infancy. Studies in healthy fullterm, small-for-gestational age and preterm infants aged 7 to 240 days.

Serum concentrations of thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3), thyroxine-binding globulin (TBG), prealbumin (TBPA) and albumin (Alb) were determined in 492 blood samples from 127 fullterm (FT), 91 small-for-gestational age (SGA) and 88 preterm (PT) healthy infants aged 7 to 240 days. Serum T4 decreased about 20% during the first month of life. In infants aged 7--49 days, serum T4 concentrations were significantly lower in SGA than in FT infants, and even lower values were found in PT infants. Serum T3 increased 50--70% reaching maximal values by 50--79 days of life. Serum T3 levels were higher in FT than in SGA infants throughout the observation period. In PT infants serum T3 increased from low values to levels which exceeded those of SGA and FT infants by 120--240 days of life. Serum TSH level did not change with age and was less than or equal to 5 mU/l in all infants. Serum TBG values were high compared to normal adult values and did not change significantly with age. Comparable serum TBG values were found in FT, SGA and PT infants. Serum TBPA increased with age. Serum TBPA increased gradually in FT infants. In SGA infants serum TBPA increased from low values to levels which by 120--240 days of life exceeded those of PT and FT infants. In PT infants a decrease in serum TBPA appeared before the rise commenced. Serum Alb increased gradually in FT, SGA and PT infants during the observation period. Serum Alb in PT infants aged 30--119 days was lower than those in FT infants with similar ages. These physiological changes in serum concentrations of thyroid hormones and hormone-binding proteins during early infancy should be considered when interpreting thyroid function tests in infants with various maturity.     

Smoking during pregnancy--effects on the fetal thyroid function

Infants delivered at term by mothers smoking at least 10 cigarettes daily during pregnancy (n = 46) were found to be growth retarded compared to infants of non-smoking mothers (n = 49), birthweights 3,445 +/- 385 (SD) g and 3,667 +/- 392 g respectively (p less than 0.05) in the two groups. Cord serum thyrotropin (TSH) was significantly decreased (8.2 +/- 4.0 U/l vs. 10.3 +/- 4.9 U/l) and free thyroxine index (FT4I)/TSH ratio significantly increased (18.8 +/- 9.0 vs. 14.4 +/- 7.6) (p less than 0.05) in the smoking group compared to infants of non-smokers. Cord serum thyroxine (T4) and FT4I were higher in the smoking group (149.0 +/- 22.4 nmol/l and 125.5 +/- 14.9 respectively) compared to infants of non-smoking mothers (140.6 +/- 21.6 nmol/l and 120.0 +/- 16.5 respectively), with borderline statistical significance (0.05 less than p less than 0.10). The results indicate that infants of smoking mothers may have a hyperfunction of the thyroid gland at birth compared to infants of non-smokers, with a negative feed-back on TSH production from the pituitary gland. Increased metabolic rate and oxygen consumption caused by fetal thyroid hyperfunction may be pathogenetic factors for the fetal growth retardation caused by maternal smoking.     

CHANGES IN SERUM CONCENTRATIONS OF THYROID HORMONES AND THYROID HORMONE-BINDING PROTEINS DURING EARLY INFANCY Studies in Healthy Fullterm, Small-for-gestational Age and Preterm Infants Aged 7 to 240 Days

Abstract. Serum concentrations of thyrotropin (TSH), thyroxine (T₄), triiodothyronine (T₃), thyroxine-binding globulin (TBG), prealbumin (TBPA) and albumin (Alb) were determined in 492 blood samples from 127 fullterm (FT), 91 small-for-gestational age (SGA) and 88 preterm (PT) healthy infants aged 7 to 240 days. Serum T ₄ decreased about 20% during the first month of life. In infants aged 7–49 days, serum T₄ concentrations were significantly lower in SGA than in FT infants, and even lower values were found in PT infants. Serum T ₃ increased 50–70% reaching maximal values by 50–79 days of life. Serum T₃ levels were higher in FT than in SGA infants throughout the observation period. In PT infants serum T₃ increased from low values to levels which exceeded those of SGA and FT infants by 120–240 days of life. Serum TSH level did not change with age and was 5 mU/1 in all infants. Serum TBG values were high compared to normal adult values and did not change significantly with age. Comparable serum TBG values were found in FT, SGA and PT infants. Serum TBPA increased with age. Serum TBPA increased gradually in FT infants. In SGA infants serum TBPA increased from low values to levels which by 120–240 days of life exceeded those of PT and FT infants. In PT infants a decrease in serum TBPA appeared before the rise commenced. Serum Alb increased gradually in FT, SGA and PT infants during the observation period. Serum Alb in PT infants aged 30–119 days was lower than those in FT infants with similar ages. These physiological changes in serum concentrations of thyroid hormones and hormone-binding proteins during early infancy should be considered when interpreting thyroid function tests in infants with various maturity.     

Serum free T4 and thyroid stimulating hormone levels in preterm infants and relationship between these levels and respiratory distress syndrome

BACKGROUND: There have been few studies of the thyroid stimulating hormone (TSH) surge in extremely low-birthweight (ELBW) infants, and the relationship between thyroid hormones and respiratory distress syndrome (RDS) has yet to be clarified. The present study sought to determine the serum levels of free T4 (fT4) and TSH in ELBW infants and to examine the relationship between these levels and the development of RDS. METHODS: The authors measured serum fT4 and TSH levels soon after birth in 449 preterm infants, who were born at 22-36 weeks of gestation, and determined the associations between these levels, the incidence of RDS, and the recognized clinical factors associated with RDS. RESULTS: Serum fT4 and TSH levels, and the fT4/TSH ratio, in the group at 22-24 weeks of gestation were significantly lower than those in the group at 28-36 weeks. The levels and ratio increased significantly with increasing gestational age. There were significant correlations between the serum fT4 level and the birthweight, Apgar score, and gender, and between the serum TSH level and the gestational age, mode of delivery, and birthweight. No significant relationship between the incidence of RDS and the serum levels of fT4 and TSH was observed. CONCLUSION: The authors' results suggest that the serum levels of fT4 and TSH in ELBW infants are very low, and that these levels are not correlated with the occurrence of RDS.     

Congenital hypothyroidism. Therapeutic strategy at the early stage of treatment

The aim of this work was to determine the optimum dosage of L-thyroxine (L-T4) given to infants with congenital hypothyroidism (CH). Thirty seven hypothyroid infants diagnosed through the French screening programme for CH have been treated in our clinic. The study analysed the biochemical parameters (TSH, FT4, FT3) and the L-T4 doses during the first year of life. Treatment was started at 23 days of age (range: 13 to 37). A dose of 7.5 micrograms/kg/d of L-T4 was given at diagnosis. After 2 weeks of treatment, FT3 was normal and FT4 at the upper limit of the normal values. At that time, TSH plasma levels were normal (less than 6 micro UI/ml) in 47% of cases. After 1.7 month of treatment, 22% of patients had TSH levels greater than 10 micro UI/ml despite normal FT4 and FT3. This group of patients, despite being given an identical L-T4 dose, had a significantly lower FT4. They were not different from those who normalized TSH levels in terms of etiology, delayed bone maturation and levels of FT4 or FT3 at diagnosis. In conclusion, an initial dose of 7.5 micrograms/kg of L-T4 normalized FT4, FT3 and TSH in 80% of our patients. Twenty percent of patients seem to need more L-T4 to bring TSH levels back to normal at the end of the second month of treatment.     

Postnatal thyroid function in low birth weight infants: A cross-sectional assessment of free thyroxine and thyroid hormone binding globulin

To investigate the significance of low serum thyroxine in premature infants, serum FT4, T4, TSH and TBG were measured in 7 infants with BW<1000 g, 8 infants with BW 1001 to 1350 g, 9 infants with BW 1351 to 2499 g, and 11 full-term infants.FT4 concentrations were lower in the LBW infants than in the FT infants. Percent FT4 values in the infants with BW<1000 g were the highest in the groups studied, so that FT4 concentrations in those infants did not fall proportionally with the marked T4 decrease. TBG concentrations were lower in the VLBW infants (相似文献   

Comparison of T4, T3, rT3 and TSH concentrations in cord blood and serum of infants up to 3 months of age

T4, T3, TSH and rT3 concentrations were measured by radioimmunoassay in cord and postnatal (8--94 days of age) serum samples from randomly selected normal newborn infants (Group I). T4 and TSH levels also were determined in cord and postnatal sera from an additional group of apparently healthy infants 8--260 days of age, whose cord serum T4 levels were in the upper or lower 10% of the normal range of values (Group II). Postnatal T4, T3 and TSH concentrations were stable over this age range; there were no significant differences between male and female infant samples. However, there was a significant decrease in serum rT3 concentrations from 8 to 50 days of age. For the Group I infants, there were significant positive correlations between cord serum T4 and postnatal serum T4 levels, cord serum TSH and postnatal serum TSH levels, and cord serum rT3 and postnatal serum rT3 concentrations. For Group II infants, a significant positive correlation was found for cord T4--postnatal T4 serum concentrations.     

惠州地区不同胎龄早产儿甲状腺功能检测及影响因素分析

目的 探讨不同胎龄早产儿甲状腺功能特点及其影响因素。方法 选择本院新生儿科2012年1~12月收治的早产儿为研究对象。按胎龄分为28~31周组、32~34周组及35~36周组,选取同期本院产科出生的健康足月新生儿30名为对照组。分别在生后第1天和第14天检测新生儿静脉血血清游离三碘甲状腺原氨酸（FT3）、游离甲状腺激素（FT4）以及促甲状腺激素（TSH）,并分析其影响因素。结果 各组新生儿生后14天血清FT3、FT4、TSH水平均显著低于生后第1天（P〈0.05）。35~36周组和对照组生后第1、14天血清FT3、FT4水平均高于28~31周组和32~34周组,32~34周组高于28~31周组（P〈0.05）。TSH水平生后第1天35~36周组和对照组高于28~31周组和32~34周组,生后第14天28~31周组和32~34周组高于35~36周组和对照组（P〈0.05）。早产儿生后第1天影响甲状腺功能的因素为胎龄、出生体重及窒息、缺氧缺血性脑病、呼吸窘迫征综合征、休克等严重疾病;生后第14天影响因素为胎龄和出生体重。结论 早产儿下丘脑-垂体-甲状腺轴发育不成熟,生后14天检测甲状腺功能具有重要临床意义。     

Tracheal lavage and plasma fibronectin: relationship to respiratory distress syndrome and development of bronchopulmonary dysplasia

Plasma for fibronectin determinations was obtained from 39 neonates with uncomplicated respiratory distress syndrome (RDS) and from 15 infants with RDS who developed bronchopulmonary dysplasia (BPD). Tracheal lavage fibronectin and albumin concentrations were measured in 15 infants with RDS and 15 with BPD. Control plasma fibronectin values were obtained from 20 healthy preterm infants on days 1, 2, 3, 14, and 30 of life. Control tracheal lavage fibronectin and albumin concentrations were measured in 17 neonates of various gestational ages who required tracheal intubation for nonpulmonary indications. Mean plasma fibronectin concentrations from patients with RDS was 121 +/- 11 micrograms/ml on days 1, 2, and 3, versus control level of 163 +/- 12 micrograms/ml (P less than 0.01). Mean tracheal lavage fibronectin/albumin ratio was 3.8 +/- 0.6 ng per microgram of albumin on days 1 to 5 for infants with RDS, versus control level of 5.6 +/- 3.6 (P = NS). Tracheal lavage fibronectin/albumin ratio from patients with BPD was elevated at 16.3 +/- 5.0 ng fibronectin per microgram of albumin on days 14 to 21, and 23.6 +/- 7.4 on day 30 (P less than 0.05 versus control and and versus RDS days 1 to 10). Low plasma fibronectin concentrations early in RDS may contribute to the development of pulmonary capillary leak. High tracheal lavage fibronectin levels may foster the development of pulmonary fibrosis in patients with BPD.     

Prolactin in umbilical cord blood and the respiratory distress syndrome.

Prolactin was measured in umbilical cord serum obtained from 77 newborn infants of gestational age 28 to 40 weeks. A positive correlation with gestational age was demonstrated. Between 30 and 36 weeks of gestation the elevation of the regression line of the concentration of cord PRL versus gestation age was significantly lower (P less than 0.05) for those infants who developed respiratory distress syndrome compared to the regression line for infants who did not develop RDS. Between 32 and 33.5 weeks, the mean +/- SEM cord PRL concentration in infants who developed RDS (101.7 +/- 9.5 ng/ml) was significantly less (P less than 0.025) than the PRL concentration in those who did not develop RDS (161.8 +/- 18.9 ng/ml). Cord PRL did not correlate with cord cortisol or dehydroepiandrosterone sulfate concentrations. Cord growth hormone concentrations did not show any relationship to the occurrence of RDS. Serum PRL was not suppressed in a further 114 infants whose mothers were treated prenatally with betamethasone. These findings raise the possibility of a role of PRL in fetal lung maturation.     

Thyroid hormones and thyroglobulin autoantibodies in insulin dependent diabetes mellitus

Serum T4, FT4, T3, and TSH were measured in a group of children with insulin dependent diabetes mellitus and a control group. In the insulin dependent diabetes mellitus group, serum T3 concentration was significantly lower than the control values. Serum T4, FT4 and TSH level did not differ. The difference in serum T3 concentration was significant between diabetic children with good or poor control. Thyroglobulin antibodies were investigated in diabetic children by Serono's "hTg antibodies" kit. Thyroglobulin antibodies were present in 14.5%. TSH concentration did not differ in antibody positive and negative cases, but one child with diabetes had evidence of moderately impaired thyroid reserve.     

Raised serum TSH in hypothyroidism.

It is desirable to detect early hypothyroidism of the mildest degree even before conventional tests of thyroid function become abnormal. Serum TSH levels (normal: undetectable to 4 muU/ml) rise in patients with mild hypothyroidism long before serum T4 and T3 levels fall. In the patient described the serum TSH level was 310 muU/ml, while other tests of thyroid function gave normal results. After treatment with thyroxine, serum TSH returned to normal. It should now be accepted that patients with mild hypothyroidism have a raised serum TSH and that thyroid insufficiency can be confidently excluded if the serum TSH concentration is normal. It is thus important to assay serum TSH when suspicion of hypothyroidism is aroused.     

Intellectual development and thyroid function in children who were breast-fed by thyrotoxic mothers taking methimazole

OBJECTIVE: Recent studies have shown normal thyroid function in infants whose mothers receive methimazole (MMI) during breast-feeding. This study evaluates the long-term effect of MMI on thyroid function and intellectual development of such children. DESIGN AND METHODS: Eighty-two children aged between 48 and 86 months were studied. Forty-two children had been breast-fed while their thyrotoxic lactating mothers received daily doses of MMI 20-30 mg in the first, 10 mg in the second and 5-10 mg for additional 10 months of therapy. Thyroid function of infants remained normal during the one year of MMI therapy of their mothers. Forty other infants served as controls. Serum T4, T3, and TSH concentrations, urinary iodine, thyroid antibodies, intelligence quotient (IQ), verbal and functional (performance) components (Wechsler and Goodenough tests) were measured in all children of the two groups. RESULTS: Height, weight, serum T4, T3, TSH and antithyroid antibody titers were not different between children in the two groups. The mean IQ was 107 +/- 17 vs 106 +/- 16 (Goodenough test) and 103 +/- 10 vs 103 +/- 16 (Wechsler test) for children of thyrotoxic mothers and control children, respectively. There was no difference in verbal and functional IQ and their components between children of thyrotoxic MMI treated mothers and control children. CONCLUSION: Thyroid function and physical and intellectual development of breast-fed infants whose thyrotoxic lactating mothers were treated with 20-30 mg doses of MMI daily are normal at age 48 to 86 months.     

Thyroid function tests in preterm infants born to preeclamptic mothers with placental insufficiency

OBJECTIVE: Since preeclampsia causes placental insufficiency, it can be hypothesized that it decreases placental passage of thyroxine (T4) from mother to infant and thus may deepen the transient hypothyroxinemia seen in preterm infants after birth. The aim of this study was to compare thyroid function tests of preterm infants born to preeclamptic mothers with placental insufficiency with preterm infants born to mothers without placental insufficiency. METHODS: Thirty-one preterm infants born to preeclamptic mothers with placental insufficiency were included in the study (group I) and 31 preterm infants born to mothers without placental insufficiency were included as the control group (group II). Thyroid hormone levels were assayed from blood samples obtained from the women before birth and thereafter from the infants at delivery (cord) and on the 1st, 3rd, 7th, and 21st days of life. RESULTS: Cord blood triiodothyronine (T3), free T3 (FT3) and free thyroxine (FT4) levels in group I were lower than in group II, whereas thyrotropin (TSH) and thyroxine binding globulin (TBG) levels were higher. No statistical difference in hormone levels studied at postnatal 1st, 3rd, 7th, and 21st day was found between the two groups. CONCLUSION: Low levels of thyroid hormones and high level of TSH in cord blood in premature infants born to preeclamptic mothers with placental insufficiency suggest intrauterine hypothyroidism. Increase in TSH and thyroid hormone concentrations after birth reveal that the hypothalamic-pituitary-thyroid axis is intact.     

Serum concentrations of thyrotropin, thyroid hormones and thyroid hormone-binding proteins during acute and recovery stages of idiopathic respiratory distress syndrome.

A total number of 27 premature infants with idiopathic respiratory distress syndrome (IRDS) and 52 healthy controls with comparable gestational age and body weights were studied during the first month of life. In infants with IRDS a reduced thyrotropin (TSH) response to birth was suggested, as serum TSH was lower in IRDS patients than in controls during the first two days of life. Low serum concentrations of thyroid hormones were found in the acute stage of IRDS reaching minimal values by day 3--5. After that period an increase in thyroid hormone levels occurred. The serum T2 increased to the level of healthy prematures by day 6--10, whereas the serum T4 increased to normal levels by day 21--30. Serum concentrations of thyroxine-binding globulin (TBG) were significantly lower in IRDS patients than in healthy controls; a gradual increase to normal levels occurred during recovery. Serum prealbumin (TBPA) levels in IRDS infants increased rapidly after birth and exceeded levels of healthy infants. Serum albumin values were not significantly different in the two groups of infants. The serum T4/TBG ratios were low during recovery from IRDS.