Newborn Screening TSH Values Less Than 15 mIU/L Are Not Associated With Long-term Hypothyroidism or Cognitive Impairment

Dynamic Screening of Thyroid Function for the Timely Diagnosis of Congenital Hypothyroidism in Very Preterm Infants: A Prospective Multicenter Cohort Study

Background: Preterm infants presented a high prevalence of congenital hypothyroidism (CH), while the optimal screening pattern is still under debate. This study aimed at evaluating the characteristics of thyroid function by conducting weekly screening during the first month of life in very preterm infants (VPIs) to achieve timely diagnosis and treatment of CH. Methods: A prospective cohort study was carried out on VPIs born with gestational age (GA) <32 weeks (w) and admitted to the participating institutes from January 1, 2019 to December 31, 2022. Serial serum thyroid hormone levels were measured weekly within the first month after birth, and at 36 w of corrected age, or before discharge. Datasets for serial thyroid hormone levels and general information were obtained. Results: A total of 5992 VPIs were enrolled in this study, of which 456 (7.6%) [95% confidence interval (CI), 6.9-8.3%] were diagnosed with CH. The incidence of CH increased with lower GA, moving from 4.8% [CI, 3.4-6.1%] at GA 31 w to 16.9% [CI, 8.3-25.4%] at GA <26 w. Among the CH subjects, 57.7% [CI, 53.1-62.2%] were identified after the first screening and classified as delayed thyrotropin elevation (dTSH). With the decrease of GA, the proportion of dTSH also increased, moving from 38.1% [CI, 27.5-48.7%] at GA 31 w to 82.6% [CI, 65.8-99.4%] at GA <26 w. Through conducting weekly screening of thyroid function, it was remarkable that only 42.3% [CI, 37.8-46.9%] of CH subjects were diagnosed during the first screening. The cumulative rate of CH identified by rescreening performed at the second, third, and fourth week was 76.1% [CI, 72.2-80.0%], 90.6% [CI, 87.9-93.3%], and 98.9% [CI, 97.9-99.9%], respectively. Conclusion: The incidence of CH and dTSH both increase with lower GA in VPIs. Dynamic screening of thyroid function by weeks within the first month of life is crucial for the timely diagnosis and treatment of CH in VPIs, and it might effectively reduce the implications of missed diagnosis and delayed treatment. Clinical Trials Registration: ChiCTR1900025234 and ChiCTR2000037918 (Registration number).

Outcomes of lowered newborn screening thresholds for congenital hypothyroidism

BACKGROUND

Newborn screening (NBS) has largely eliminated the physical and neurodevelopmental effects of untreated congenital hypothyroidism (CH). Many countries, including Australia, have progressively lowered NBS bloodspot thyroid-stimulating hormone (b-TSH) thresholds. The impact of these changes is still unclear.

OBJECTIVES

To evaluate the performance of CH NBS following the reduction of b-TSH thresholds in New South Wales (NSW) and the Australian Capital Territory (ACT), Australia, from 15 to 8 mIU/L, and to determine the clinical outcomes of cases detected by these thresholds.

METHODS

NBS data of 346 849 infants born in NSW/ACT, Australia from 1 November, 2016-1 March, 2020 inclusive were analysed. A clinical audit was conducted on infants with a preliminary diagnosis of CH born between 1 January, 2016-1 December, 2020 inclusive.

RESULTS

The lowered b-TSH threshold (≥8 mIU/L, ~99.5th centile) detected 1668 infants (0.48%), representing an eight-fold increase in recall rate, of whom 212 of 1668 (12.7%) commenced thyroxine treatment. Of these 212 infants, 62 (29.2%) (including eight cases with a preliminary diagnosis of thyroid dysgenesis) had an initial b-TSH 8-14.9 mIU/L. The positive predictive value for a preliminary diagnosis of CH decreased from 74.3% to 12.8% with the lowered threshold. Proportionally, more pre-term infants received a preliminary CH diagnosis on screening with the lower threshold (16.1% of 62) than with the higher threshold (8.0% of 150).

CONCLUSION

Clinically relevant CH was detected using the lowered threshold, albeit at the cost of an eight-fold increase in recall rate. Further clinical and economic studies are required to determine whether benefits of lowered screening thresholds outweigh potential harms from false-positive results on infants, their families and NBS programs.

The impact of prolonged, maternal iodine exposure in early gestation on neonatal thyroid function

CONTEXT

Hysterosalpingography (HSG) using oil-soluble contrast medium (OSCM) improves pregnancy rates but results in severe and persistent iodine excess, potentially impacting the fetus and neonate.

OBJECTIVE

To determine the incidence of thyroid dysfunction in newborns conceived within six months of OSCM HSG.

DESIGN

Offspring study of a prospective cohort of women who underwent OSCM HSG.

SETTING

Auckland region, New Zealand (2020-2022).

PARTICIPANTS

Offspring from the SELFI (Safety and Efficacy of Lipiodol in Fertility Investigations) study cohort (n=57).

MEASUREMENTS

All newborns had a dried blood spot card for TSH measurement 48 hours after birth as part of New Zealand's Newborn Metabolic Screening Programme. Forty-one neonates also had a heel prick serum sample at one week to measure thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3). Maternal urine iodine concentration (UIC) and TSH in the six months after OSCM HSG were retrieved from the SELFI study for analyses.

PRIMARY OUTCOME

Incidence of hypothyroidism in the neonatal period.

RESULTS

There was no evidence of primary hypothyroidism on newborn screening (TSH 2-10 mIU/L). All neonates tested at one week had normal serum TSH, FT4, and FT3 levels. However, increasing maternal peak UIC levels during pregnancy were associated with lower TSH levels (p= 0.006), although also associated with lower FT4 levels (p=0.032).

CONCLUSIONS

While pre-conceptional OSCM HSG in women did not result in neonatal hypothyroidism, gestational iodine excess was associated with a paradoxical lowering of neonatal TSH levels despite lower FT4 levels. These changes likely reflect alterations in deiodinase activity in the fetal hypothalamic-pituitary axis from iodine excess.

TRIAL REGISTRATION

https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12620000738921, identifier 12620000738921.

Congenital Hypothyroidism: Screening and Management

ABSTRACT

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Prompt diagnosis by newborn screening (NBS) leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet established in all countries globally. Seventy percent of neonates worldwide do not undergo NBS.The initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism.Newborn screening alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

Clinical survey of current practice regarding treatment of children with borderline thyroid abnormalities

AIM

Recently, there has been debate about reducing newborn screening (NBS) thyroid-stimulating hormone (TSH) cut-offs to identify children with mild, but potentially clinically significant, thyroid deficiency. Once identified by NBS, these children will be referred to paediatric endocrinologists for further testing and possible treatment; however, variation in current clinical practice is not known. The aim of this study is to survey Paediatric Endocrinologists in Australia and New Zealand to gain insight into clinical practice for the treatment of mild thyroid deficiency.

METHODS

A piloted questionnaire was sent to members of the Australasian Paediatric Endocrinologist Group. The survey asked the Australasian Paediatric Endocrinologist Group members about the investigations performed, treatment and follow-up for infants with different confirmatory serum TSH levels.

RESULTS

There were 42 completed surveys, a response rate of 34%. When presented with four case studies, 7% of clinicians would treat a child with confirmatory serum TSH of 8.7 mU/L with thyroxine, 69% would treat a child with confirmatory serum TSH 21.4 mU/L, 76% would treat a child with confirmatory serum TSH 24.3 mU/L and 95% would treat a child with confirmatory serum TSH 44.7 mU/L.

CONCLUSION

This contemporary survey of clinicians regarding the treatment of mild thyroid deficiency in children has shown that clinical practice varies extensively. International and national guidelines on the treatment of congenital hypothyroidism should be updated to incorporate new evidence and ensure consistency across clinical practice.

Intervención de enfermería en tamiz metabólico neonatal: Revisión integrativa

Introducción: El tamiz metabólico neonatal es el conjunto de procedimientos y pruebas que se realizan para separar entre recién nacidos aparentemente sanos, aquellos con sospecha de errores innatos del metabolismo. Por tanto, permite detectar la enfermedad antes que se manifieste e iniciar tratamiento oportuno para evitar complicaciones, discapacidad y muerte. Actualmente, es un programa neonatal prioritario para la salud infantil. En la etapa operativa, la estandarización de criterios es determinante para resultados confiables. Objetivo: Realizar revisión bibliográfica integrativa de la intervención de enfermería en tamiz metabólico neonatal. Metodología: Investigación integrativa en las bases de datos Web of Science, Scielo, Scopus, Pubmed, Sciencedirect, Dialnet, OVID y EBSCO, utilizando los descriptores tamizaje neonatal, atención de enfermería, errores innatos del metabolismo, neonatología y analgesia; con los operadores booleanos and, or y not. De 116 documentos obtenidos, 36 cumplen criterios de elegibilidad y representan el material de estudio. Resultados: La recolección de muestra de sangre para tamiz se realiza entre el tercer y quinto día de vida, esencialmente mediante punción capilar del talón. Las medidas analgésicas no farmacológicas son lactancia materna, método canguro y contención. La muestra debe protegerse de contaminación, y su estabilidad depende de la temperatura de conservación hasta su análisis. Conclusiones: La literatura científica revisada, faculta al profesional de enfermería para proporcionar atención integral y segura al recién nacido que participa en el programa.

Fifty years of newborn screening for congenital hypothyroidism: current status in Australasia and the case for harmonisation

OBJECTIVES

Since its implementation 50 years ago in Quebec, Canada, newborn screening for congenital hypothyroidism has become one of the most successful public health measures worldwide. Screening programmes across Australia and New Zealand are characterised by significant commonalities in screening algorithms, and a high degree of regional cooperation in harmonisation efforts. We aimed to conduct a comprehensive survey of current performance and practices related to the total testing process for congenital hypothyroidism screening and provide recommendations for harmonisation priorities within our region.

METHODS

A survey was conducted involving the six newborn screening laboratories which provide complete geographic coverage across Australasia. Approximately 360,000 newborns are screened annually. Survey questions incorporated pre-analytical, analytical, and post-analytical aspects of the screening programmes and an extensive 5-year (2016-2020) retrospective analysis of individual programme performance data. Responses from individual screening programmes were collated.

RESULTS

The uptake of newborn screening was over 98% for the six major jurisdictions. All programmes have adopted a single-tier thyroid stimulating hormone (TSH) strategy using the Perkin Elmer GSP instrument. Significant similarities exist between programmes for recommended age of collection and recollection protocols for low birthweight newborns. The process for the determination of TSH cutoffs varies between programmes. TSH lower cut-offs for borderline-positive and positive notifications between 12-15 and 12-25 mIU/L blood, respectively. Recall rates vary between 0.08 and 0.20%. The case definition for congenital hypothyroidism generally includes biochemical and radiological parameters in addition to the commencement of thyroxine. All programmes reported collecting biochemical and clinical data on infants with positive screening tests, and positive predictive values vary between 23.6 and 77.3%. Variation in reported incidence (1:1,300-2,000) cannot be entirely explained by cutoff or recall rate (although one programme reporting fewer cases includes only permanent disease).

CONCLUSIONS

Despite similarities between newborn screening algorithms for congenital hypothyroidism across Australia and New Zealand, differences in reported programme performance provide the basis for further harmonisation. Surveillance of a large population offers the potential for the ongoing development of evidence-based screening guidelines.

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.

Predictors of transient congenital primary hypothyroidism: data from the German registry for congenital hypothyroidism (AQUAPE "HypoDok")

Neonatal screening for congenital primary hypothyroidism (CH) may not distinguish between transient (TCH) and permanent dysfunction (PCH), causing potential overtreatment and concerns in affected families. To specify the indication for interruption of therapy, we analysed the German registry "HypoDok" for infants with CH, which oversees 1625 patients from 49 participating centres in Germany and Austria from 1997 until today. A total of 357 patients with a thyroid gland in loco typico were identified and retrospectively grouped according to cessation (TCH, n = 24) or continuation (PCH, n = 333) of L-thyroxine (L-T4) treatment at 2 years of age. The receiver operating characteristic (ROC) analysis was performed to identify cutoffs predicting TCH by screening TSH concentrations and L-T4 dosages. Gestational ages, birth weights and prevalence of associated malformations were comparable in both groups. The cutoff screening TSH concentration was 73 mU/L. The cutoff daily L-T4 dosage at 1 year was 3.1 μg/kg (90% sensitivity, 63% specificity; 36 μg/day) and at 2 years of age 2.95 μg/kg (91% sensitivity, 59% specificity; 40 μg/day). At 2 years of age, specificity (71%) increased when both of these parameters were considered together.Conclusion: The decision to continue or cease L-T4 treatment at 2 years of age in CH patients diagnosed in neonatal screening may be based on their screening TSH concentrations and individual L-T4 dosages at 1 and 2 years of age. Thus, TCH and PCH may be distinguished; overtreatment avoided; and affected families reassured. What is Known: • The course of congenital primary hypothyroidism may be transient, causing potential overtreatment. • The dose of l-thyroxine at 1 or 2 years of age may predict a transient course of primary congenital hypothyroidism. What is New: • TSH screening concentration and l-thyroxine dosages at 1 and 2 years of age represent reliable predictors for transient congenital primary hypothyroidism with higher sensitivity and specificity when considered together in order to select eligible patients who qualify for treatment withdrawal.

[Neonatal screening for congenital hypothyroidism]

Congenital hypothyroidism (CH) is the leading cause of preventable mental retardation. It is mainly due to thyroid dysgenesis or dyshormonogenesis with normally located gland, and detected at birth in developed countries by systematic neonatal screening. The early treatment of patients with CH has successfully improved the prognosis and management of this disease. An increase in the incidence of congenital hypothyroidism with a normally located gland has been reported worldwide over the last three decades. The etiology of CH with a normally located gland remains elusive and about half of them demonstrate spontaneous resolution of CH within a few months (transient CH). They highlight the need to reevaluate thyroid function during follow-up.