Effects of thyroxine supplementation on neurologic development in infants born at less than 30 weeks' gestation

A practical gestational age-based algorithm for timely detection of hypothyroidism in premature infants

OBJECTIVES

To assess utility and accuracy of a gestational age-based screening targeting premature infants to detect congenital hypothyroidism.

STUDY DESIGN

A prospective cohort study was conducted in infants <35 weeks' gestational age with clinical outcomes at 2-3 years of age. Patients received newborn screenings at 24 hours and 10-14 days of life. Free T4 (FT4) and thyroid-stimulating hormone (TSH) levels were measured at one month of life and repeated based on algorithm by corrected gestational age.

RESULTS

Among infants <35 weeks gestation (n = 938), the incidence of hypothyroidism requiring treatment was 1:58. TSH levels at one month of age was predictive of treatment (AUC 0.96, 95% CI 0.88-1). The optimal TSH threshold of 8 mIU/L (8 µU/ml) increased the specificity to 0.97 and sensitivity to 0.88. Following initiation of treatment for hypothyroidism during NICU hospitalization, 43.8% (n = 7) were diagnosed with permanent congenital hypothyroidism.

CONCLUSIONS

Our study supports a gestational age-based screening algorithm for early detection of hypothyroidism in premature infants.

Clinical indicators that influence a clinician's decision to start L-thyroxine treatment in prematurity with transient hypothyroxinemia

BACKGROUND

Transient hypothyroxinemia of prematurity (THOP) is defined as a low level of circulating thyroxine (T4), despite low or normal thyroid-stimulating hormone (TSH) levels.

AIMS

We aimed to evaluate the incidence of THOP, the clinical and laboratory findings of preterm infants with this condition and the levothyroxine (L-T4) treatment.

METHODS

Preterm infants (n = 181) delivered at 24-34 weeks of gestation were evaluated by their thyroid function tests that were performed between the 10th and 20th days of postnatal life and interpreted according to the gestational age (GA) references. Clinical and laboratory characteristics of the patients with THOP and normal thyroid function tests were compared. Patients with THOP and treated with L-T4 were compared with the ones who were not regarding laboratory, and clinical characteristics.

RESULTS

Incidence of hypothyroxinemia of prematurity was 45.8% (n = 83). Euthyroidism, primary hypothyroidism, and subclinical hypothyroidism were diagnosed in 47.5% (n = 86), 5% (n = 9) and 1.7% (n = 3) of the patients, respectively. Mean birth weight (BW) and GA were significantly lower in the hypothyroxinemia group than in the euthyroid group (p < 0.001). L-T4 was started in 43% (n = 36) of the patients with THOP. Treatment initiation rate was 44.4% (n = 16) in 24-27 wk, 41.6% (n = 15) in 28-30 wk, and 13.8% (n = 5) in 31-34 wk. As the GA increased, the incidence of THOP and the rate of treatment initiation decreased (p < 0.001). The lowest free thyroxine (FT4) cut-off value was 0.72 ng/dl in the treated group. In addition, incidences of vancomycin + amikacin, caffeine, dopamine treatments, RDS, IVH, BPD, central catheter, FFP transfusion, and ventilator support were higher in the treated group (P < 0.05).

CONCLUSION

This study revealed that prevalence of THOP increased as the GA and BW decreased. As the GA decreased, THOP patients requiring L-T4 treatment increased. Additionally, association with comorbid diseases increased the requirement of treatment.

Guidelines for Newborn Screening of Congenital Hypothyroidism (2021 Revision)

Purpose of developing the guidelines: Newborn screening (NBS) for congenital hypothyroidism (CH) was started in 1979 in Japan, and early diagnosis and treatment improved the intelligence prognosis of CH patients. The incidence of CH was once about one in 5,000-8,000 births, but has been increased with diagnosis of subclinical CH. The disease requires continuous treatment and specialized medical facilities should conduct differential diagnosis and treatment in patients who are positive by NBS to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, the guidelines were revised in 2014. Here, we have added minor revisions to the 2014 version to include the most recent findings. Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients.

Effect of levothyroxine supplementation in extremely low birth weight infants with transient hypothyroxinemia of prematurity

This study aimed to determine the short- and/or long-term outcomes of levothyroxine replacement therapy in extremely low birth weight (ELBW) infants with transient hypothyroxinemia of prematurity (THOP). The medical records of 335 ELBW infants with THOP were reviewed retrospectively to identify whether levothyroxine treatment affects short- and/or long-term outcomes at a corrected age of 2 years. The infants were arbitrarily grouped based on thyroxine (T4) (free T4 [fT4]) levels into group 1 (n = 142), which included infants with T4 (fT4) levels < 2.5 (0.5) ng/dl, and group 2 (n = 193), which included those with T4 (fT4) levels ranging from ≥ 2.5 (0.5) ng/dl to < 4.5 (0.9) ng/dl. Levothyroxine replacement therapy was not associated with beneficial short- or long-term outcomes in ELBW infants with THOP. Short-term outcomes, such as mortality and composite morbidities, and long-term outcomes, such as failure to achieve catch-up height at a corrected age of 2 years, were significantly higher in group 1 than in group 2, regardless of levothyroxine treatment status. Levothyroxine replacement therapy is not associated with short-or long-term advantages in ELBW infants with THOP. This study suggests that the severity of THOP may be the major determinant of adverse outcomes in ELBW infants with THOP, rather than levothyroxine treatment.

Lack of association between gestational age adjusted TSH percentiles and neurodevelopmental outcomes among preterm infants

BACKGROUND

Limited evidence exists on whether subclinical hypothyroidism suggested by mildly elevated TSH levels affect neurodevelopment and growth in preterm infants. The objective of this study was to determine the association between gestational age adjusted TSH percentiles and neurodevelopmental outcomes among preterm infants.

METHODS

Univariate linear regression analysis was conducted to determine, in infants born less than thirty-two weeks gestational age, the correlation between the TSH percentile on the last newborn screen and neurodevelopmental assessment scores and growth outcomes at eighteen to twenty-two months of corrected age.

RESULTS

Seventy-four patients were enrolled in the study with a mean gestational age of 28.8 weeks. There was no correlation between the last TSH percentile value and Bayley-III cognitive composite score or other neurodevelopmental or growth outcomes.

CONCLUSION

In a cohort of preterm infants, higher TSH percentiles suggesting potential subclinical hypothyroidism did not predict any adverse effect on neurodevelopmental or growth outcomes.

Effects of oral iodine supplementation in very low birth weight preterm infants for the prevention of thyroid function alterations during the neonatal period: results of a randomised assessor-blinded pilot trial and neurodevelopmental outcomes at 24 months

The trace element iodine (I) is essential for the synthesis of thyroid hormones. Parenteral nutrition solutions, formula milk, and human breast milk contain insufficient iodine to meet recommended intake for preterm infants. Iodine deficiency may affect thyroid function and may be associated with morbidity or neurological outcomes. The primary objective is to assess the evidence that dietary supplementation with iodine affects thyroid function during the neonatal period. The design was a randomised controlled pilot trial. Infants who met the inclusion criteria were enrolled through consecutive sampling and assigned to two different groups. The setting was a Spanish university hospital. Ninety-four patients with very low birth weight (under 1500 g) were included. Intervention group: 30 µg I/kg/day of iodine in oral drops given to 47 infants from their first day of life until hospital discharge. Control group: 47 infants without supplements. Formula and maternal milk samples for the determination of iodine content were collected at 1, 7, 15, 21, 30 days, and at discharge. Blood samples were collected for thyroid hormones. Neurological development was assessed at 2 years of age (Bayley III Test). Infants in the supplemented group reached the recommended levels from the first days of life. The researchers detected the effects of iodine balance on the plasma levels of thyroid hormones measured during the first 12 weeks of age. The trial assessed the impact of the intervention on neurodevelopmental morbidity.Conclusion: Thyroid function is related to iodine intake in preterm infants. Therefore, supplements should be added if iodine intake is found to be inadequate. The analyses found no effects of iodine supplementation on the composite scores for Bayley-III assessments in all major domains. The study results indicate potentially important effects on language development related to low iodine excretion during the first 4 weeks of life What is Known: • Thyroid function is related to iodine intake in preterm infants. • Preterm babies on formula preparations and with exclusive parenteral nutrition are at high risk of iodine deficiency. What is New: • Iodine intake should be monitored during the neonatal period. • Iodine supplements should be added if iodine intake is found to be inadequate.

Recovery of the brain after intraventricular hemorrhage

Intraventricular hemorrhage (IVH) remains a major complication of prematurity, worldwide. The severity of IVH is variable, ranging from a tiny germinal matrix bleed to a moderate-to-large ventricular hemorrhage or periventricular hemorrhagic infarction. Survivors with IVH often suffer from hydrocephalus and white matter injury. There is no tangible treatment to prevent post-hemorrhagic cerebral palsy, cognitive deficits, or hydrocephalus in these infants. White matter injury is attributed to blood-induced damage to axons and maturing oligodendrocyte precursors, resulting in reduced myelination and axonal loss. Hydrocephalus results from obstructed CSF circulation by blood clots, increased CSF production, and reduced CSF absorption by lymphatics and arachnoid villi. Several strategies to promote neurological recovery have shown promise in animal models, including the elimination of blood and blood products, alleviating cerebral inflammation and oxidative stress, as well as promoting survival and maturation of oligodendrocyte precursors. The present review integrates novel mechanisms of brain injury in IVH and the imminent therapies to alleviate post-hemorrhagic white matter injury and hydrocephalus in the survivors with IVH.

Cord Blood Thyroid Hormones and Neurodevelopment in 2-Year-Old Boys and Girls

Objective: Thyroid hormones are essential for neurodevelopment in early life. However, the impact of mild alterations in neonatal thyroid hormones on infant neurodevelopment and its sex dimorphism is unclear. We aimed to assess whether mild variations in neonatal thyroid hormones of term-born newborns with maternal euthyroid are related to neurodevelopment in 2-year-old boys and girls.

Methods: This study used data from 452 singleton term-born infants of mothers with normal thyroid function in Shanghai, China, and their follow-up measure at the age of 2 years. Cord serum concentrations of free thyroxine (FT4), free triiodothyronine (FT3), thyroid-stimulating hormone (TSH), and thyroid peroxidase antibody (TPOAb) were measured by chemiluminescent microparticle immunoassays and classified into three groups: the low (1st, Q1), middle (2nd−4th, Q2–Q4), and high (5th, Q5) quintiles. Neurodevelopment indices were assessed using the Ages and Stages Questionnaire, third edition (ASQ-3), at 24 months of age.

Results: Compared to infants with thyroid hormones in the middle (Q2–Q4), boys with FT4 in the lowest quintile had 5.08 (95% CI: 1.37, 8.78) points lower scores in the communication domain, 3.25 (0.25,6.25) points lower scores in the fine motor domain, and 3.84 (0.04, 7.64) points lower scores in the personal-social domain, respectively. Boys with FT3 in the highest quintile had 4.46 (0.81, 8.11) points increase in the personal-social domain. These associations were not observed in girls. No associations were observed between cord blood serum TSH and ASQ-assessed neurodevelopment in the boys or the girls.

Conclusions: Mild alterations in thyroid hormones of newborns were associated adversely with neurodevelopment in boys, suggesting the importance of optimal thyroid hormone status for neurodevelopment in early life.

Nonthyroidal Illness Syndrome: To Treat or Not to Treat? Have We Answered the Question? A Review of Metanalyses

BACKGROUND AND OBJECTIVE

Nonthyroidal Illness Syndrome (NTIS) occurs in approximately 70% of patients admitted to Intensive Care Units (ICU)s and has been associated with increased risk of death. Whether patients with NTIS should receive treatment with thyroid hormones (TH)s is still debated. Since many interventional randomized clinical trials (IRCT)s were not conclusive, current guidelines do not recommend treatment for these patients. In this review, we analyze the reasons why TH treatment did not furnish convincing results regarding possible beneficial effects in reported IRCTs.

METHODS

We performed a review of the metanalyses focused on NTIS in critically ill patients. After a careful selection, we extracted data from four metanalyses, performed in different clinical conditions and diseases. In particular, we analyzed the type of TH supplementation, the route of administration, the dosages and duration of treatment and the outcomes chosen to evaluate the results.

RESULTS

We observed a marked heterogeneity among the IRCTs, in terms of type of TH supplementation, route of administration, dosages and duration of treatment. We also found great variability in the primary outcomes, such as prevention of neurological alterations, reduction of oxygen requirements, restoration of endocrinological and clinical parameters and reduction of mortality.

CONCLUSIONS

NTIS is a frequent finding in critical ill patients. Despite several available IRCTs, it is still unclear whether NTIS should be treated or not. New primary endpoints should be identified to adequately validate the efficacy of TH treatment and to obtain a clear answer to the question raised some years ago.

Hypothyroxinemia Detected at 4 Weeks of Life in Preterm Infants Born at Less than 30 Weeks of Gestation

OBJECTIVE

Data on free thyroxine (FT4) concentrations beyond first 2 weeks of preterm infants are limited. This study was aimed to describe the association between perinatal characteristics and FT4 concentrations and the incidence of hypothyroxinemia at 4 weeks.

STUDY DESIGN

Retrospective analysis of serum thyroid function tests at 4 weeks in preterm infants <30 weeks of gestation. Association between FT4 at 4 weeks of life and perinatal characteristics were determined by bivariate analysis and multivariable regression. Incidence of hypothyroxinemia was determined using a gestational age adjusted definition based on in utero levels at the equivalent postmenstrual age.

RESULTS

The study cohort consisted of 280 infants. FT4 concentrations at 4 weeks of life were significantly associated with gestational age, birth weight, gender, and maternal history of thyroid disease. Hypothyroxinemia was found in 32.8% of the study cohort.

CONCLUSION

Perinatal characteristics are associated with FT4 concentrations at 4 weeks of life. Nearly one-third of infants born <30 weeks had hypothyroxinemia at 4 weeks of life when compared with in utero levels at the equivalent postmenstrual age.

Thyroid function and dysfunction in preterm infants-Challenges in evaluation, diagnosis and therapy

Thyroid hormone levels have a crucial role for optimal brain development from gestation through the first 2 postnatal years. However, thyroid hormones vary with gestational age, and their levels vary between term and preterm infants. Preterm newborns are prone to thyroid dysfunction which is now more frequently observed with the advances of neonatal care and improved survival of extremely premature infants. Thus, hypothyroxinaemia of prematurity associated with delayed TSH elevation is very common in low birth weight premature infants most likely due to the immaturity of the hypothalamic-pituitary thyroid axis. Furthermore, postnatal illness, medications and iodine status may contribute to the thyroid dysfunction or affect the interpretation of the thyroid function tests. Despite available guidelines, timing of screening and optimal treatment of thyroid dysfunction in premature infants remains controversial. Furthermore, it is unknown whether untreated thyroid dysfunction in premature babies affects neurodevelopmental outcome. In the vast majority of preterm infants, hypothyroxinaemia is transient; however, permanent hypothyroidism due to thyroid dysgenesis or enzyme defects might also occur. Therefore, careful monitoring of thyroid function and long-term follow-up is needed to assess an appropriate therapeutic approach. This article reviews thyroid physiology in preterm infants, the influences of gestation and other neonatal conditions on thyroid function tests, optimal timing of screening and possible predictors to differentiate transient hypothyroxinaemia from permanent hypothyroidism.

Newborn Screening for Congenital Hypothyroidism in Japan

Congenital hypothyroidism (CH) is the most common preventable cause of intellectual impairment or failure to thrive by early identification and treatment. In Japan, newborn screening programs for CH were introduced in 1979, and the clinical guidelines for newborn screening of CH were developed in 1998, revised in 2014, and are currently undergoing further revision. Newborn screening strategies are designed to detect the elevated levels of thyroid stimulating hormone (TSH) in most areas of Japan, although TSH and free thyroxine (FT4) are often measured simultaneously in some areas. Since 1987, in order not to observe the delayed rise in TSH, additional rescreening of premature neonates and low birth weight infants (<2000 g) at four weeks of life or when their body weight reaches 2500 g has been recommended, despite a normal initial newborn screening. Recently, the actual incidence of CH has doubled to approximately 1:2500 in Japan as in other countries. This increasing incidence is speculated to be mainly due to an increase in the number of mildly affected patients detected by the generalized lowering of TSH screening cutoffs and an increase in the number of preterm or low birth weight neonates at a higher risk of having CH than term infants.

White matter injury in infants with intraventricular haemorrhage: mechanisms and therapies

Intraventricular haemorrhage (IVH) continues to be a major complication of prematurity that can result in cerebral palsy and cognitive impairment in survivors. No optimal therapy exists to prevent IVH or to treat its consequences. IVH varies in severity and can present as a bleed confined to the germinal matrix, small-to-large IVH or periventricular haemorrhagic infarction. Moderate-to-severe haemorrhage dilates the ventricle and damages the periventricular white matter. This white matter injury results from a constellation of blood-induced pathological reactions, including oxidative stress, glutamate excitotoxicity, inflammation, perturbed signalling pathways and remodelling of the extracellular matrix. Potential therapies for IVH are currently undergoing investigation in preclinical models and evidence from clinical trials suggests that stem cell treatment and/or endoscopic removal of clots from the cerebral ventricles could transform the outcome of infants with IVH. This Review presents an integrated view of new insights into the mechanisms underlying white matter injury in premature infants with IVH and highlights the importance of early detection of disability and immediate intervention in optimizing the outcomes of IVH survivors.

The Laboratory Features of Congenital Hypothyroidism and Approach to Therapy

Congenital hypothyroidism (CH) is one of the most common preventable causes of intellectual disability. Thyroid hormone is required for normal brain development, but neonates with CH typically appear healthy at birth, which leads to delays in diagnosis and treatment. In developed countries, newborn screening programs have led to earlier diagnosis and treatment of CH, resulting in improved neurodevelopmental outcomes. Neonates with an abnormal newborn screen require prompt confirmatory serum thyroid function tests and treatment with thyroid hormone. Further evaluation for the etiology of CH should not delay treatment decisions.

Thyroid Function in Preterm/Low Birth Weight Infants: Impact on Diagnosis and Management of Thyroid Dysfunction

Maternal thyroid hormone crosses the placenta to the fetus beginning in the first trimester, likely playing an important role in fetal development. The fetal thyroid gland begins to produce thyroid hormone in the second trimester, with fetal serum T4 levels gradually rising to term. Full maturation of the hypothalamic-pituitary-thyroid (HPT) axis does not occur until term gestation or the early neonatal period. Postnatal thyroid function in preterm babies is qualitatively similar to term infants, but the TSH surge is reduced, with a corresponding decrease in the rise in T4 and T3 levels. Serum T4 levels are reduced in proportion to the degree of prematurity, representing both loss of the maternal contribution and immaturity of the HPT axis. Other factors, such as neonatal drugs, e.g., dopamine, and non-thyroidal illness syndrome (NTIS) related to co-morbidities contribute to the "hypothyroxinemia of prematurity". Iodine, both deficiency and excess, may impact thyroid function in infants born preterm. Overall, the incidence of permanent congenital hypothyroidism in preterm infants appears to be similar to term infants. However, in newborn screening (NBS) that employ a total T4-reflex TSH test approach, a higher proportion of preterm babies will have a T4 below the cutoff, associated with a non-elevated TSH level. In NBS programs with a primary TSH test combined with serial testing, there is a relatively high incidence of "delayed TSH elevation" in preterm neonates. On follow-up, the majority of these cases have transient hypothyroidism. Preterm/LBW infants have many clinical manifestations that might be ascribed to hypothyroidism. The question then arises whether the hypothyroxinemia of prematurity, with thyroid function tests compatible with either non-thyroidal illness syndrome or central hypothyroidism, is a physiologic or pathologic process. In particular, does hypothyroxinemia contribute to the neurodevelopmental impairment common to preterm infants? Results from multiple studies are mixed, with some randomized controlled trials in the most preterm infants born <28 weeks gestation appearing to show benefit. This review will summarize fetal and neonatal thyroid physiology, thyroid disorders specific to preterm/LBW infants and their impact on NBS for congenital hypothyroidism, examine treatment studies, and finish with comments on unresolved questions and areas of controversy.

Antenatal corticosteroids for threatened labour facilitate thyroid maturation among preterm neonates

OBJECTIVE

To examine the effect of antenatal corticosteroids (ANS) on the maturation of thyroid function in the preterm infants.

CONTEXT

ANS reduce mortality and morbidities in preterm neonates. Organ maturation by the glucocorticoids is the key, at least in part. However, the effect of ANS on thyroid is controversial.

PATIENTS

A study group of 99 very low birthweight neonates (<34 weeks' gestational age) with the exception of those born more than 7 days after ANS administration were divided into a complete group (n = 49) whose mothers completed two doses of betamethasone and who were born more than 24 hours after the completion of ANS administration, and an incomplete group (n = 50) who were not exposed to any ANS or were born within 24 hours after the completion of ANS administration. Serum-free thyroxine and thyroid-stimulating hormone (TSH) levels were measured, and thyrotropin-releasing hormone (TRH) stimulation tests were performed at about 2 weeks of age.

RESULTS

The incidence of hyperthyrotropinaemia (TSH > 15 mIU/L) in the complete group was significantly lower than in the incomplete group (6% vs 22%, P = .023). Exaggerated responses to TRH tests were more frequent in the incomplete group (17% vs 44%; P = .053). TSH₃₀ was significantly lower in the complete group, (P = .046). Multivariate logistic regression analysis showed that the incidence of hyperthyrotropinaemia was associated with complete ANS administration (adjusted odds ratios 0.39).

CONCLUSIONS

ANS administration might facilitate thyroid maturation in preterm neonates.

Thyroid function in preterm infants and neurodevelopment at 2 years

OBJECTIVES

Postnatal thyroid dysfunction is common in preterm infants but the relationship between mild dysfunction and neurodevelopment is unclear. Our aim is to describe the relationship between thyroid function and neurodevelopment.

DESIGN

Cohort analysis.

PATIENTS

1275 infants born under 31 weeks' gestation; there were no exclusion criteria.

SETTING

The infants were part of a UK daily iodine supplementation trial.

MAIN OUTCOMES

Thyroid-stimulating hormone, thyroid-binding globulin and total thyroxine levels were measured in dried blood spots on postnatal days 7, 14, 28 and the equivalent of 34 weeks' gestation. Neurodevelopment was measured using the Bayley-III Scales of infant development at 2 years of age.

RESULTS

No infant was identified as hypothyroid through routine screening. The 3% of infants consistently in the top decile of gestationally age-adjusted thyroid-stimulating hormone levels had a reduction in cognitive score of 7 Bayley units when compared with those not in the top decile (95% CI -13 to -1). A reduction in motor composite score of 6 units (95% CI -12 to <-0.1) and fine motor score of 1 unit (95% CI -2 to -0.1) was also identified. The 0.7% of infants consistently in the bottom decile of age-adjusted thyroxine levels had a reduction in motor composite score of 14 units (95% CI -25 to -2) and its two subset scores, fine and gross motor, of 2 units (95% CI respectively -4.5 to <-0.1 and -4.3 to -0.3).

CONCLUSIONS

Preterm infants with consistent 'mild' thyroid dysfunction score less on neurodevelopmental tests at 2 years of age. Many of these infants will not be detected by current clinical protocols or screening programmes.

Neurodevelopmental Outcomes at 42 Months After Thyroxine Supplementation in Infants Below 28 Weeks' Gestation: A Randomized Controlled Trial

Background: Infants below 28 weeks' gestation have low thyroid hormone plasma levels compared with more mature infants and this may contribute to their risk of developmental disability. We aimed at determining the effect of supplementation with levothyroxine (LT4) for extremely premature infants born below 28 weeks' gestations on neurodevelopmental outcomes at 42 months. Methods: An explanatory double-blind, randomized, placebo-controlled trial consecutively recruited 153 infants below 28 weeks' gestation from 5 neonatal units in the United Kingdom. Infants were either supplemented with LT4 started intravenously during the first 5 days after birth and then changed to oral LT4 when enteral feeds were fully established (8 μg/kg birthweight/day as a single daily dose) or given placebo until 32 weeks' corrected gestational age. Neurodevelopmental outcomes at 42 months (range 40-43) were evaluated in 59 of these infants (30 LT4-supplemented, 29 placebo) by using Bayley III Mental and Psychomotor Developmental Indices. Cognition outcomes was correlated with plasma free thyroxine (fT4) level at 36 weeks and diffusion tensor imaging (DTI) markers. Results: The LT4 supplemented group performed significantly better in motor, language, and cognitive function domains. The mean of the difference between each group (95% confidence intervals [CI], p-value) was motor domain 6.96 ([0.55-13.38], p = 0.034); language domain 8.93 ([0.16-17.70], p = 0.041); and cognition domain 6.35 ([0.14-12.55], p = 0.045). Neurodevelopmental outcome at 42 months had some associations with the trial's primary outcome (subarachnoid space width and motor outcome, p = 0.03), plasma fT4 level at 36 weeks (fT4 and cognition outcome, p = 0.01), and DTI at 36 weeks with cognition outcomes (p > 0.05). Conclusion: Our data suggest that early supplementation with LT4 may improve long-term neurodevelopment in infants born below 28 weeks' gestation, but larger trials are warranted as the current reported improvements shown are not strong enough to warrant a change in practice.

General Movement assessment and neurodevelopmental trajectory in extremely preterm infants with hypothyroxinaemia of prematurity (THOP)

BACKGROUND

Transient hypothyroxinaemia of prematurity (THOP) has been associated with neurodevelopmental deficits with a paucity of literature leading to variable practice.

AIM

Evaluation of the relationship between free T4 (fT4) levels at 2 weeks after birth and early markers of neurodevelopmental outcome.

STUDY DESIGN

A retrospective study of prospectively collected data from infants born <29 weeks' gestation, admitted to NICU between January 2012 and December 2014. The primary outcomes were the relationship between fT4 levels at 2 weeks, Prechtl General Movement Assessment (GMA) at 36 weeks and 3 months postterm age, and Bayley Scales of Infant Development (BSID-III) at 2 years postterm age. Secondary outcomes were survival free of disability and other neonatal morbidities.

RESULTS

Of 122 infants, 101 infants had normal fT4 levels (No-THOP) and 21 had fT4 levels >1SD below the mean (THOP group). There was increased frequency of abnormal GMA in the No-THOP group compared with the THOP group at 36 weeks (abnormal writhing GMs: 43% vs 21%, p = 0.15) and 3 months corrected age (absent fidgety GMs: 7.6% vs 0%, p = 0.36), though not statistically significant. The neurodevelopmental outcome was worse in the No-THOP group compared with the THOP group with significantly lower mean cognitive and motor scores at 2 year of corrected age (90 ± 13.8 vs 100 ± 8.3, p = 0.01 and 91 ± 15.2 vs 100 ± 13.2, p = 0.04 respectively).

CONCLUSIONS

This is the first report describing General Movements (GMs) in preterm infants with THOP. We found worse neurodevelopmental outcome in No-THOP infants reflected by significantly worse cognitive and motor outcomes at 2 years corrected age.

Determining Reference Ranges for Total T4 in Dried Blood Samples for Newborn Screening

The purpose of this study was to define reference intervals for total thyroxine (tT4) in dried blood samples (DBSs) obtained for newborn screening. The aim of our study was to assess the possible benefit of measuring tT4 concentrations directly in DBSs obtained for newborn screening in premature and term-born infants. In order to have a sufficient number of samples for the extremely premature infants (<30 weeks), we set up a retrospective study, measuring the concentrations in DBSs collected over the previous 21 weeks. This time frame was a result of the included miniature study of tT4 stability in DBSs. We found that tT4 strongly correlated with gestational age (GA) in premature infants, highlighting the need for age-specific reference ranges. For term-born infants, the tT4 ranges did not vary significantly among different gestational ages, allowing for the use of one single reference range.

Thyroxine Threshold Is Linked to Impaired Outcomes in Preterm Infants

Transient hypothyroxinaemia of prematurity (THOP) presents as decreased free thyroxine without an increase in thyroid stimulating hormone. Thyroxine availability is important in case of premature birth, and THOP could be associated with impaired adaptation to extra-uterine life but the association of thyroxine level and clinical status has not yet been clearly defined. Aim: To defined a free thyroxine threshold likely associated with neonatal clinical impairment and outcomes at age three years. Methods: This retrospective cohort study included infants born before or at 28 weeks' gestation at the Regional Maternity in Nancy, France. We defined a free thyroxine threshold as a function of clinical impairment by Receiver Operating Curve analysis, validated by log likelihood iteration in binary logistic regression, in infants born from October 2008 to December 2012 and meeting neonatal clinical impairment criteria. This threshold was validated in a distinct cohort of infants born from January 2014 to December 2016. Clinical impairment was defined as assisted ventilation requirement at seven days of age plus four minor clinical disorders among heart rate, blood pressure, temperature, serum sodium and potassium, APGAR score at five minutes, vasopressor treatment and patent ductus arteriosus. The first cohort was assessed at age three years for neurodevelopmental outcomes. Results: We identified a ≤10 pmol/L threshold with 85.7% sensitivity and 51% specificity. From the first and second cohorts, 196 and 176 infants respectively had available data, and 85% (97/112) and 26% (20/78) with free thyroxine ≤10 pmol/L met clinical impairment criteria. For infants with values >10 pmol/L, 41% (35/84) and 3% (3/98) from the first and second cohorts met impairment criteria. Of 147 children with available data at age 3 years, 65% (58/89) with neonatal free thyroxine ≤10 pmol/L had adverse neurodevelopmental outcomes vs. 34% (20/58) with >10 pmol/L (OR 3.55; 95% confidence interval, 1.77-7.13; p < 0.001). Conclusion: A free thyroxine level ≤10 pmol/L in infants is associated with neonatal clinical impairment and poor outcome at age three years.

Nonthyroidal Illness Syndrome Across the Ages

In conditions of acute illness, patients present with reduced plasma T3 concentrations without a concomitant rise in TSH. In contrast, plasma concentrations of the inactive hormone rT3 increase, whereas plasma concentrations of T4 remain low-normal. This constellation of changes, referred to as nonthyroidal illness syndrome (NTIS), is present across all ages, from preterm neonates and over-term critically ill infants and children to critically ill adults. Although the severity of illness strongly correlates with the severity of the NTIS phenotype, the causality of this association remains debated, and pathophysiological mechanisms remain incompletely understood. In the acute phase of illness, NTIS appears to be caused predominantly by an increased peripheral inactivation of thyroid hormones, in which reduced nutritional intake plays a role. Current evidence suggests that these acute peripheral changes are part of a beneficial adaptation of the body to reduce expenditure of energy and to activate the innate immune response, which is important for survival. In contrast, in more severely ill and prolonged critically ill patients, an additional central suppression of the thyroid hormone axis alters and further aggravates the NTIS phenotype. Recent studies suggest that this central suppression may not be adaptive. Whether treatment of this central component of NTIS in prolonged critically ill patients, with the use of hypothalamic releasing factors, improves outcome remains to be investigated in large randomized control trials.

Initial and delayed thyroid-stimulating hormone elevation in extremely low-birth-weight infants

BACKGROUND

To determine the incidence, etiology, and outcomes of thyroid-stimulating hormone (TSH) elevation in extremely low-birth-weight infants (ELBWIs).

METHODS

Newborn thyroid screening data of 584 ELBWIs (birth weight, < 1000 g; gestational age, ≥ 23 weeks) were retrospectively analyzed to identify initial (≤ 2 postnatal weeks) and delayed (> 2 weeks) TSH elevations. Growth and neurodevelopmental outcomes at 2 years' corrected age (CA) were assessed according to levothyroxine replacement.

RESULTS

Initial and delayed TSH elevations were detected at CAs of 27 and 30 weeks, respectively, with incidence rates of 0.9 and 7.2%, respectively. All infants with initial TSH elevations had perinatal asphyxia, and 95% of those with delayed TSH elevation were exposed to various stressors, including respiratory support, drugs, and surgery within 2 weeks before diagnosis of TSH elevation. Free thyroxine (T4) levels were simultaneously reduced in 80 and 57% of infants with initial and delayed TSH elevations, respectively. Both initial and delayed TSH elevations were transient, regardless of levothyroxine replacement. Infants receiving levothyroxine replacement therapy had significantly higher TSH elevations, significantly lower free T4 levels, and significantly reduced mortality, compared to untreated infants. However, levothyroxine replacement had no significant effect on long-term growth and neurodevelopmental outcomes.

CONCLUSIONS

The timing of insult superimposition on hypothalamic-pituitary-thyroid axis maturation is a major determinant of initial or delayed TSH elevation in ELBWIs. Levothyroxine replacement did not affect growth or neurodevelopmental outcomes in this population.

Incidence and severity of transient hypothyroxinaemia of prematurity associated with survival without composite morbidities in extremely low birth weight infants

This study investigated the incidence of transient hypothyroxinaemia of prematurity (THOP) associated with survival without composite morbidities and the predictability of THOP severity in extremely low birth weight infants (ELBWIs). We retrospectively reviewed the medical records of 546 ELBWIs who underwent initial thyroid function tests within 14 postnatal days, with 156 ELBWIs from 2000 to 2005 (period I) and 390 from 2006 to 2013 (period II). The infants were stratified into 23–24, 25–26 and 27–28 weeks’ gestation subgroups within each period; the initial thyroxine (T4) level, mortality, clinical characteristics and composite morbidities, including bronchopulmonary dysplasia, intraventricular haemorrhage, necrotizing enterocolitis, and retinopathy of prematurity were analysed. The predictive value of the initial T4 level, Apgar score at 5 min, and clinical risk index for babies II (CRIB II) score for estimating mortality and survival with or without composite morbidities was assessed. Comparing period II and period I, the incidence of THOP was significantly decreased along with significantly increased survival without composite morbidities in ELBWIs at 25–28 weeks’ gestation. The severity of THOP showed significant associations with mortality and composite morbidities. The initial T4 level was most effective for predicting outcome compared with Apgar and CRIB II scores.

Evolution of circulating thyroid hormone levels in preterm infants during the first week of life: perinatal influences and impact on neurodevelopment

Background For several decades, transient hypothyroxinemia of prematurity (THOP) has been a topic of debate. The pathophysiology is incompletely understood and consensus on the therapeutic approach is lacking. This study aimed at gaining a better insight into the pathogenesis by studying the trends in thyroid hormone (TH) levels during the first week of life. Methods This single-center prospective observational study analyzed the plasma levels of total thyroxine (T4) and free thyroxine (fT4), total triiodothyronine (T3), thyroid-stimulating hormone (TSH) and T4-binding globulin (TBG) in cord blood and at the end of the first week of life in 120 preterm infants (gestational age [GA] <37 weeks). The change over time was calculated (delta, ∆). The impact of perinatal and subsequently postnatal variables on ∆ was studied by hierarchical multiple regression. The impact of ∆ on the neurodevelopmental outcome at the corrected ages of 9 and 24 months, measured by the Bayley Scales of Infant Development (BSID)-II, was assessed by logistic regression. Results ∆fT4 levels were negatively affected by GA and use of dopamine, whereas only GA was associated with low ∆T3 levels. Negative ∆fT4 levels were present in 75% of the extremely low-for-gestational-age infants, whereas 23.5% had a negative ∆T3 level. There was an increased risk for an abnormal mental developmental score (<85) with decreasing ∆T3 at 9 months, corrected age, but not at 24 months. Conclusions A negative evolution in circulating TH levels is principally an immaturity phenomenon, whereas dopamine can further suppress the hypothalamic-pituitary-thyroid axis. There is at least a temporary negative effect of this evolution on the infants' neurodevelopment.

Review shows that thyroid hormone substitution could benefit transient hypothyroxinaemia of prematurity but treatment strategies need to be clarified

AIM

Thyroid hormones are crucial for foetal and neonatal brain development. This paper provides an overview of the normal role of thyroid hormones in foetal brain development and the pathophysiology of transient hypothyroxinaemia of prematurity (THOP). It also discusses the diagnostic and therapeutic controversies around THOP and looks at directions for future research.

METHODS

We used the PubMed and Embase databases to identify papers published in English from 1969 to June 2018. This identified 20 papers about the impact of THOP on neurodevelopment and seven randomised controlled trials about therapeutic approaches from 1981-2016.

RESULTS

THOP has been researched for more than three decades. The impact of temporarily low thyroxine levels, without any increase in pituitary-secreted thyroid-stimulating hormone at a critical timeframe in an infant's brain development, is still debated. Heterogeneity in THOP definitions, difficulties with thyroid hormone assessment, identifying patients at risk and a clear lack of sufficiently powered studies add to the current controversy. There are indications that thyroid hormone substitution might be useful in extremely low gestational age neonates with THOP.

CONCLUSION

Some preterm infants could benefit from THOP treatment, but more studies are needed to clarify further treatment strategies, including the optimal timing of initiation and duration.

Screening and management of thyroid dysfunction in preterm infants

Preterm infants can suffer various thyroid dysfunctions associated with developmental immaturity of the hypothalamic-pituitary-thyroid axis, postnatal illness, medications, or iodine supply. The incidence of thyroid dysfunction among preterm infants is higher than that among term infants and has been increasing with improvement in the survival of preterm infants. Hypothyroxinemia is frequently observed during the first week of life in extreme preterm neonates, and the incidence of delayed thyrotropin elevation is high at the age of 2-6 weeks. Although the necessity of routine rescreening remains controversial, recent guidelines on screening for congenital hypothyroidism have recommended rescreening of all preterm neonates. Thyroid hormone replacement is recommended for persistent thyrotropin elevation with or without hypothyroxinemia. Hypothyroxinemia without thyrotropin elevation does not require treatment, and some potential risks of levothyroxine supplementation have been reported. Although most thyroid dysfunctions are transient, careful follow-up after discontinuation of levothyroxine is considered so as to avoid missing persistent hypothyroidism.

Neonatal effects of thyroid diseases in pregnancy and approach to the infant with increased TSH: Turkish Neonatal and Pediatric Endocrinology and Diabetes Societies consensus report

Thyroid functions in the fetus and newborn carry importance in terms of the baby's health and development of the central nervous system. Maternaliodine deficiency, exposure to iodine, thyroid diseases (Hashimoto thyroiditis, Graves') and drugs used by the mother affect thyroid functions in the fetus. Reflections of these effects are observed immediately after delivery. Investigation of the mother in terms of thyroid diseases during pregnancy, recognition and appropriate assessment of the required conditions, screening of all newborns in the first days of life in terms of congenital hypothyroidism, timely and appropriate evaluation of the screening results, early diagnosis and appropriate treatment of cases of congenital hypothyroidism, assessment and management of cases of transient thyroid hormone disorders and close monitoring of the thyroid functions and development of patients in whom treatment has been initiated with a diagnosis of hypothyroidism are crucial in terms of developmental outcomes of the babies who have thyroid function disorders or hypothyroidism. This guideline was written with the objective of guiding pediatricians, neonatologists and pediatric endocrinologists in the issue of assessment, diagnosis and management of thyroid function disorders and thyroid diseases concerning the fetus and baby during gestation and neonatal period.

Higher Incidence Rates of Hypothyroidism and Late TSH Rise in Preterm Very-Low-Birth-Weight Infants at a Tertiary Care Center

BACKGROUND/AIMS

Preterm newborns with a very low birth weight (VLBW) of < 1,500 g have an atypical form of hypothyroidism with a delayed rise in TSH, necessitating a second newborn screening specimen collection. The aims of this study were to survey the compliance with second newborn screening to detect delayed TSH rise in VLBW preterm infants at a tertiary care center, and to determine the rate of atypical hypothyroidism.

METHODS

Retrospective review of the records of 104 preterm VLBW infants. Late TSH rise was defined as an increase in TSH concentration after 14 days of age in the presence of a normal initial screen.

RESULTS

The compliance rate was 92% for the second screening. High rates of hypothyroidism (16.3%) and of late TSH rise (4.8%) were detected. Patients with hypothyroidism had a significantly lower birth weight (p = 0.01) and longer hospital stay (p = 0.004). Patients with late versus those with early TSH rise had a significantly lower mean birth weight (851 ± 302 vs. 1,191 ± 121 g, p = 0.004).

CONCLUSION

The rates of early and late TSH rise in this VLBW population were higher than those in the literature and could be due to the use of povidone-iodine disinfectants. The yield of a second TSH screening in this study was high indicating the need for vigilance in screening VLBW preterm infants.

Thyroid Function in the Neonatal Intensive Care Unit

Patients in the neonatal intensive care unit (NICU) are at high risk for abnormal thyroid function testing because of illness and preterm birth. Preterm infants are born before hypothalamic-pituitary-thyroid axis maturation and the normal feedback mechanisms that regulate thyroid hormone production remain immature. Preterm and sick infants may develop hypothyroidism even if routine thyroid screening tests collected in the first several days after birth are normal. This article reviews normal hypothalamic-pituitary-thyroid axis maturation, thyroid hormone testing and interpretation in the NICU, and the current evidence for and against levothyroxine treatment of NICU patients with borderline abnormal thyroid function testing.

Pediatric Hypothyroidism: Diagnosis and Treatment

Thyroid hormone has important physiologic functions in nearly every organ system. The critical role of thyroid hormone in growth and in physical and neurologic development lends particular importance to the prompt diagnosis and appropriate treatment of hypothyroidism in infants and children. Congenital hypothyroidism is common and has potentially devastating neurologic consequences. While the approach to diagnosis and treatment of severe congenital hypothyroidism is well established, data continue to emerge about the genetic causes, clinical significance, and prognosis of the milder forms of congenital hypothyroidism that are increasingly being diagnosed by newborn screening. Similarly, the diagnosis and treatment of severe acquired hypothyroidism is straightforward and clearly of clinical benefit, but uncertainty remains about the optimal management of mild subclinical hypothyroidism. This review summarizes current knowledge of the causes, clinical manifestations, diagnosis, treatment, and prognosis of hypothyroidism in infants and children, with a focus on recent developments and areas of uncertainty in this field.

Effect of L-thyroxine supplementation on very low birth weight infants with transient hypothyroxinemia of prematurity at 3 years of age

OBJECTIVE

To evaluate the effects of levothyroxine (L-T4) supplementation on growth and neurodevelopmental outcomes at 3 years of age in very low birth weight (VLBW) infants with transient hypothyroxinemia of prematurity (THOP).

STUDY DESIGN

VLBW infants with plasma thyroid-stimulating hormone concentrations <10 mIU l^-1 and free thyroxine concentrations <0.8 ng dl^-1 were defined as having THOP and randomly assigned to the Treated (20 infants) or Untreated (31 infants) group. The Treated group received L-T4 at a dose of 5 μg kg^-1 day^-1. Growth and neurodevelopmental outcomes at 3 years of age were compared between the two groups.

RESULTS

There were no significant differences in body length, body weight or head circumference mean s.d. scores or in neurodevelopmental outcomes between the two groups.

CONCLUSION

L-T4 supplementation in VLBW infants with THOP demonstrated no beneficial effect at 3 years of age.

Late-onset circulatory collapse of prematurity

Late-onset circulatory collapse (LCC) is a refractory hypotension occurring after the early neonatal period (>day 7), in very low-birthweight infants. Typically, infants stabilized within the early neonatal period develop sudden onset of circulatory collapse after the early neonatal period. The underlying pathophysiology of LCC is considered to be relative adrenal insufficiency, which is well known in Japan, but is not widely accepted in North America or Europe. The current increase in LCC in Japan suggests that the principal trigger is related to recent trends in neonatal medicine and/or newly introduced treatments for preterm infants, but the pathophysiology has not been fully elucidated. In this review, based on current knowledge regarding LCC, the pathophysiology is discussed.

Congenital hypothyroidism with delayed thyroid-stimulating hormone elevation in premature infants born at less than 30 weeks gestation

OBJECTIVE

Congenital hypothyroidism (CH) with delayed thyroid-stimulating hormone (TSH) elevation is a common form of thyroid dysfunction among premature infants. Routine newborn screening (NBS) may miss infants with CH with delayed TSH elevation. The objective of the study is to determine the prevalence of CH with delayed TSH elevation in premature infants and to identify associated risk factors.

STUDY DESIGN

Retrospective analysis of serum thyroid function screening (TFS) at day of life 30 in premature infants <30 weeks gestation, admitted to University of Iowa Neonatal Intensive Care Unit between 1 July 2012 to 30 June 2015. Serum free thyroxine and TSH levels were obtained in premature infants <30 weeks gestation on day of life 30. Follow-up testing and pediatric endocrinology consultation were done according to the institutional protocol.

RESULT

In total, 286 infants were included. All infants underwent routine NBS and 280 patients underwent TFS. Twenty-six patients (9.1%) were diagnosed with thyroid dysfunction. NBS identified only three patients. CH with delayed TSH elevation was diagnosed in 20 patients (6.9%) and was significantly associated with multiple gestation, lower birth weight, higher gestational age and lower 5 min APGAR score.

CONCLUSION

Thyroid dysfunction is common among premature infants born before 30 weeks gestation. The majority of cases with thyroid dysfunction had CH with delayed TSH elevation, which was not detected by NBS. We recommend measurement of serum TSH and free T4 levels on day of life 30 in premature infants born at <30 weeks gestation to identify patients with CH with delayed TSH elevation.

Euthyroid Sick Syndrome

In this review, we discuss the characteristics, pathophysiology, and therapeutic implications of the euthyroid sick syndrome. Multiple mechanisms have been identified to contribute to the development of euthyroid sick syndrome, including alterations in the iodothyronine deiodinases, thyroid-stimulating hormone secretion, thyroid hormone binding to plasma protein, transport of thyroid hormone in peripheral tissues, and thyroid hormone receptor activity. The euthyroid sick syndrome appears to be a complex mix of physiologic adaptation and pathologic response to acute illness. The underlying cause for these alterations has not yet been elucidated. Treatment of the euthyroid sick syndrome with thyroid hormone to restore normal serum thyroid hormone levels in an effort to improve disease prognosis and outcomes continues to be a focus of many clinical studies, although currently available data do not provide evidence of a clear benefit of treatment.

No Association Between Transient Hypothyroxinemia of Prematurity and Neurodevelopmental Outcome in Young Adulthood

CONTEXT

Transient hypothyroxinemia of prematurity (THoP) has been associated with neurodevelopmental impairment in infancy and childhood. It is not known whether these relations persist into adulthood.

OBJECTIVE

The objective was to examine whether there is an effect of THoP on intelligence quotient (IQ) score and motor functioning at a young adult age.

DESIGN

This study was part of the 19-year follow-up of the Project On Preterm and Small-for-gestational-age birth (POPS) cohort, which included infants born very preterm (ie, <32 wk) and/or with a very low birth weight (ie, <1500 g).

SETTING

This was a multicenter study.

PATIENTS

There were 398 19-year-old participants of the POPS cohort, of whom 120 had THoP.

EXPOSURE

T4 concentrations were obtained through the national neonatal screening program for congenital hypothyroidism. THoP was defined as a total T4 concentration < -3 SD of the daily mean (approximately 60 nmol/L).

MAIN OUTCOME MEASURES

Main outcome measures were IQ and motor functioning, measured with the digital Multicultural Capacities Test-Intermediate Level and a revised version of Touwen's examination of minor neurological dysfunction, respectively.

RESULTS

THoP was not associated with IQ score (mean difference, 0 [95% confidence interval, -3.8 to 3.8] points) or motor function (mean difference, 0.6 [95% confidence interval, -1.3 to 2.5] points) after adjustment for demographic and perinatal characteristics.

CONCLUSIONS

No associations between THoP and neurodevelopmental outcome at age 19 years were found.

Congenital hypothyroidism: recent advances

PURPOSE OF REVIEW

This review summarizes significant recent advances in the epidemiology, pathophysiology, and treatment of congenital hypothyroidism.

RECENT FINDINGS

The apparent incidence of congenital hypothyroidism has more than doubled in recent years because of several factors, including more inclusive diagnostic criteria, shifting demographics, and increasing survival of preterm infants. The greatest increase has occurred in mildly affected patients, many of whom have a eutopic thyroid gland. Congenital hypothyroidism may be transient or persistent, but the natural history cannot be predicted by severity at diagnosis. In premature infants, who are especially vulnerable to hypothyroidism, the rise in thyroid-stimulating hormone may be delayed and therefore detected only by routine follow-up screening. Recent studies of defects in thyroid hormone synthesis have focused on the role of mutations in the dual oxidase system and of a novel apical iodide transporter, anoctamin 1. Finally, emerging data suggest that exposure to excess thyroid hormone may be as harmful as hypothyroidism to long-term cognitive development.

SUMMARY

Although newborn screening has virtually eradicated mental retardation due to congenital hypothyroidism in parts of the world, new information continues to accumulate and new questions to arise about the diagnosis, physiology, and optimal management of this disorder.

Response to thyrotropin-releasing hormone stimulation tests in preterm infants with transient hypothyroxinemia of prematurity

OBJECTIVE

Whether hormone supplementation is necessary for infants with transient hypothyroxinemia of prematurity (THOP) remains controversial, and further analysis of the hypothalamus-pituitary-thyroid axis of infants with THOP is necessary.

STUDY DESIGN

Thyrotropin-releasing hormone (TRH) stimulation tests were performed at 2 weeks of age in 50 infants with a gestational age of 30 weeks or less, and the data were analyzed retrospectively.

RESULT

Subjects were divided into three groups; group A consisted of euthyroid infants, group B consisted of infants with THOP and group C consisted of hypothyroid infants. The basal and peak thyroid-stimulating hormone level of group C in response to TRH stimulation tests was significantly higher than the others, but no differences were observed between groups A and B.

CONCLUSION

The response of infants with THOP to the TRH stimulation test was not different from that of euthyroid infants, which suggested that their hypothalamic-pituitary-thyroid axis was appropriately regulated in infants with THOP.

Interpreting Minor Variations in Thyroid Function or Echostructure: Treating Patients, Not Numbers or Images

Overt thyroid dysfunction is documented by serum thyrotropin or T4 concentrations are often ordered for nonspecific complaints and will by definition fall outside of the 95% reference range 5% of the time. In addition, most laboratories quote adult ranges, which are not necessarily applicable to young children, and regression toward the mean is common, justifying that the test be repeated before embarking on treatment. On the other hand, neck ultrasounds are frequently performed for diffuse goiter or non-thyroid conditions. Yet, an ultrasound is not required to make a diagnosis of Hashimoto thyroiditis and small cysts and nodules discovered incidentally often lead to unjustified concerns about neoplasia.

Guidelines for Mass Screening of Congenital Hypothyroidism (2014 revision)

Purpose of developing the guidelines: Mass screening for congenital hypothyroidism started in 1979 in Japan, and the prognosis for intelligence has been improved by early diagnosis and treatment. The incidence was about 1/4000 of the birth population, but it has increased due to diagnosis of subclinical congenital hypothyroidism. The disease requires continuous treatment, and specialized medical facilities should make a differential diagnosis and treat subjects who are positive in mass screening to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, new findings on prognosis and problems in the adult phase have emerged. Based on these new findings, the 1998 guidelines were revised in the current document (hereinafter referred to as the Guidelines). Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring patients to pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients.

Adrenal and thyroid function in the fetus and preterm infant

Adrenal and thyroid hormones are essential for the regulation of intrauterine homeostasis, and for the timely differentiation and maturation of fetal organs. These hormones play complex roles during fetal life, and are believed to underlie the cellular communication that coordinates maternal-fetal interactions. They serve to modulate the functional adaptation for extrauterine life during the perinatal period. The pathophysiology of systemic vasopressor-resistant hypotension is associated with low levels of circulating cortisol, a result of immaturity of hypothalamic-pituitary-adrenal axis in preterm infants under stress. Over the past few decades, studies in preterm infants have shown abnormal clinical findings that suggest adrenal or thyroid dysfunction, yet the criteria used to diagnose adrenal insufficiency in preterm infants continue to be arbitrary. In addition, although hypothyroidism is frequently observed in extremely low gestational age infants, the benefits of thyroid hormone replacement therapy remain controversial. Screening methods for congenital hypothyroidism or congenital adrenal hyperplasia in the preterm neonate are inconclusive. Thus, further understanding of fetal and perinatal adrenal and thyroid function will provide an insight into the management of adrenal and thyroid function in the preterm infant.

Thyroid hormone supplementation in preterm infants born before 28 weeks gestational age and neurodevelopmental outcome at age 36 months

BACKGROUND

Thyroid hormones are required for normal brain maturation, and neonatal plasma thyroid hormone concentrations are low in infants less than 28 weeks gestation. It is not known whether treatment of such infants with thyroid hormone improves neurodevelopmental outcome.

METHODS

At three years corrected age, mental, motor, and neurological development was assessed in infants born at less than 28 weeks gestational age who had participated in a phase 1 trial of differing doses and modes of administration of thyroid hormone. The trial's endpoints were thyroid hormone (thyroxine, T4) and thyotropin plasma concentrations in eight study arms: six treated with T4 [4, 8, and 16 μg/(kg · day)], bolus or continuous], one treated with iodine only, and one treated with placebo. Follow-up at three years was not part of the original study goals. Developmental index scores, rates of cerebral palsy (CP), and rates of adverse outcome (death or moderate to severe delay in development and/or disabling CP) were compared between the eight study groups and between groups combined by dosage level, and between infants with and without T4 supplementation.

RESULTS

Of 166 randomized infants, 32 (19%) died in the neonatal period. Of the 134 survivors, follow-up results were available for 89 children (66%). Mental and motor development and rates of cerebral palsy did not differ in any of the comparisons made.

CONCLUSION

In this study, no differences in neurodevelopment were found in relation to thyroid hormone treatment, but power was insufficient to detect any but very large differences.

Free thyroxine levels after very preterm birth and neurodevelopmental outcomes at age 7 years

BACKGROUND AND OBJECTIVES

Preterm infants commonly have transient hypothyroxinemia of prematurity after birth, which has been associated with deficits in general intellectual functioning, memory, attention, and academic achievement. However, research has predominantly focused on thyroxine levels in the first 2 weeks of life and outcomes are limited to the preschool period. Our objective was to evaluate the relationships between free thyroxine (fT₄) levels over the first 6 weeks after very preterm (VPT) birth with cognitive functioning and brain development at age 7 years.

METHODS

A total of 83 infants born VPT (<30 weeks' gestation) had fT₄ concentrations measured postnatally and 2- and 6-week area under the curve (AUC) summary measures were calculated. Follow-up at age 7 years included a neuropsychological assessment and brain MRI. Univariable and multivariable regression modeling was used where AUC for fT₄ was the main predictor of neurodevelopmental outcome at age 7 years.

RESULTS

Multivariable modeling revealed that higher, not lower, postnatal fT₄ levels (2-week AUC) were associated with poorer cognitive performances at age 7 years on tasks of verbal learning (P = .02), verbal memory (P = .03), and simple reaction time (P < .001). A similar pattern of results was found when the 6-week AUC was examined. No significant associations between postnatal fT₄ levels and brain volumes at age 7 years were identified.

CONCLUSIONS

Results are contradictory to previous observations and suggest that after adjustment for confounders, higher postnatal fT₄ levels in VPT infants, rather than lower levels, may be a marker of adverse neuropsychological development in childhood.

Failure of thyroid hormone treatment to prevent inflammation-induced white matter injury in the immature brain

Preterm birth is very strongly associated with maternal/foetal inflammation and leads to permanent neurological deficits. These deficits correlate with the severity of white matter injury, including maturational arrest of oligodendrocytes and hypomyelination. Preterm birth and exposure to inflammation causes hypothyroxinemia. As such, supplementation with thyroxine (T4) seems a good candidate therapy for reducing white matter damage in preterm infants as oligodendrocyte maturation and myelination is regulated by thyroid hormones. We report on a model of preterm inflammation-induced white matter damage, in which induction of systemic inflammation by exposure from P1 to P5 to interleukin-1β (IL-1β) causes oligodendrocyte maturational arrest and hypomyelination. This model identified transient hypothyroidism and wide-ranging dysfunction in thyroid hormone signalling pathways. To test whether a clinically relevant dose of T4 could reduce inflammation-induced white matter damage we concurrently treated mice exposed to IL-1β from P1 to P5 with T4 (20 μg/kg/day). At P10, we isolated O4-positive pre-oligodendrocytes and gene expression analysis revealed that T4 treatment did not recover the IL-1β-induced blockade of oligodendrocyte maturation. Moreover, at P10 and P30 immunohistochemistry for markers of oligodendrocyte lineage (NG2, PDGFRα and APC) and myelin (MBP) similarly indicated that T4 treatment did not recover IL-1β-induced deficits in the white matter. In summary, in this model of preterm inflammation-induced white matter injury, a clinical dose of T4 had no therapeutic efficacy. We suggest that additional pre-clinical trials with T4 covering the breadth and scope of causes and outcomes of perinatal brain injury are required before we can correctly evaluate clinical trials data and understand the potential for thyroid hormone as a widely implementable clinical therapy.

Endocrine physiology in the newborn

Evaluation of suspected endocrine pathology in newborn infants requires knowledge of the dynamic changes that characterize normal hormonal function in the neonatal period. This article reviews normal endocrine physiology as it pertains to common clinical scenarios encountered in neonatal surgical patients. Topics covered include thyroid and adrenal function as well as glucose and calcium metabolism.