L-thyroxin treatment in infants with hyperthyrotropinaemia: 4-year experience

Update on Neonatal Isolated Hyperthyrotropinemia: A Systematic Review

The purpose of this paper was to systematically summarize the published literature on neonatal isolated hyperthyrotropinemia (HTT), with a focus on prevalence, L-T4 management, re-evaluation of thyroid function during infancy or childhood, etiology including genetic variation, thyroid imaging tests, and developmental outcome. Electronic and manual searches were conducted for relevant publications, and a total of 46 articles were included in this systematic review. The overall prevalence of neonatal HTT was estimated at 0.06%. The occurrence of abnormal imaging tests was found to be higher in the persistent than in the transient condition. A continuous spectrum of thyroid impairment severity can occur because of genetic factors, environmental factors, or a combination of the two. Excessive or insufficient iodine levels were found in 46% and 16% of infants, respectively. Thirty-five different genetic variants have been found in three genes in 37 patients with neonatal HTT of different ethnic backgrounds extracted from studies with variable design. In general, genetic variants reported in the TSHR gene, the most auspicious candidate gene for HTT, may explain the phenotype of the patients. Many practitioners elect to treat infants with HTT to prevent any possible adverse developmental effects. Most patients with thyroid abnormalities and/or carrying monoallelic or biallelic genetic variants have received L-T4 treatment. For all those neonates on treatment with L-T4, it is essential to ensure follow-up until 2 or 3 years of age and to conduct medically supervised trial-off therapy when warranted. TSH levels were found to be elevated following cessation of therapy in 44% of children. Withdrawal of treatment was judged as unsuccessful, and medication was restarted, in 78% of cases. Finally, data extracted from nine studies showed that none of the 94 included patients proved to have a poor developmental outcome (0/94). Among subjects presenting with normal cognitive performance, 82% of cases have received L-T4 therapy. Until now, the precise neurodevelopmental risks posed by mild disease remain uncertain.

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.

Use of Tc-99 m thyroid scans in borderline congenital hypothyroidism

BACKGROUND

Mild or borderline congenital hypothyroidism [often referred to as mild neonatal hyperthyrotropinemia (MNH)] is characterized by an abnormal newborn screen (NBS), followed by mildly elevated TSH and normal FT4 on confirmatory testing. This condition is increasingly observed, but data regarding optimal management are limited.

OBJECTIVE

Examine the use of routine technetium thyroid scanning (TS) in the management of MNH.

METHODS

Retrospective study of infants with MNH between 2000 and 2011. We assessed the clinical course of infants with MNH according to TS results; as a comparator, infants with classic congenital hypothyroidism (CH) were analysed in parallel.

RESULTS

We identified 69 infants (52% boys) with MNH and 164 (34% boys) with classic CH. TS results were divided into four subgroups: no uptake in 7% of MNH vs 24% of classic CH (P < 0·01), decreased uptake/anatomical abnormalities in 39% vs 46% (p = NS), increased uptake in 35% vs 26% (p = NS) and normal uptake in 19% vs 4% (P < 0·01). In MNH, neither NBS-TSH, confirmatory TSH and FT4, mean LT-4 treatment doses and number of dose escalations, nor post-treatment FT4 and TSH differed among the four subgroups. In contrast, clinical features in infants with classic CH differed among the subgroups. Among MNH infants who reached 3 years of age, trial-off treatment was successful in 6 of 11 (55%) with no apparent difference in success rates among TS subgroups.

CONCLUSIONS

The information provided by TS during evaluation of MNH does not predict clinical course; obtaining these scans in infants with MNH may not be an effective use of healthcare resources.

Thyroid Functions in Healthy Infants during the First Year of Life

OBJECTIVE

To study the pattern of thyroid function testing in healthy newborns during the first year of life.

STUDY DESIGN

We used the computerized database of a health management organization. Among the 18,507 infants insured by the Clalit Health Services born in the Sheba Medical Center between 2002 and 2007, 652 full-term healthy newborns with birth weight >2 kg and no significant perinatal morbidity underwent thyrotropin (TSH) determination as outpatients in their first year of life. The Clalit Health Services database provided demographic data, laboratory results, and dispensed medications for the newborns and their mothers.

RESULTS

Initial serum TSH levels were within normal range (0.35-5.5 mIU/L) in 91.1%, elevated (> 5.5-≤ 10 mIU/L) in 8.3%, and highly elevated (>10 mIU/L) in 0.6% of the studied cohort. The 97.5 and 2.5 percentile values were 7.4 and 0.74 mIU/L, respectively. TSH measurements were repeated in 34.2%, 72.2%, and 100% of children with normal, elevated, and highly elevated initial levels, respectively; results were normal in 96%, 74%, and 50% of patients with initial normal, elevated, and highly elevated TSH, respectively; repeated TSH levels were > 97.5 percentile in 35% of patients with initial TSH > 97.5 percentile compared with 1% with first results < 97.5 percentile (P = .005). Only 4 (0.6%) of the 652 newborns included in the study received thyroxin treatment.

CONCLUSION

The normal TSH levels found in most healthy infants with normal thyroid screening and the spontaneous normalization of TSH values below 7.4 mIU/liter, substantiate the reliability of the screening, reduce unnecessary work-up and unnecessary thyroxin treatment of neonates meeting these criteria.

Mild neonatal hyperthyrotrophinaemia: 10-year experience suggests the condition is increasingly common but often transient

OBJECTIVE

To examine a large population of infants with mild neonatal hyperthyrotrophinaemia (MNH) and determine prevalence, clinical characteristics and treatment history.

METHODS

Retrospective study of infants with MNH followed at The Hospital for Sick Children between 2000 and 2011. MNH was defined by an abnormal newborn screen followed by thyroid-stimulating hormone (TSH) between 5 and 30 mU/l and normal free T4 (FT4) on confirmatory tests.

RESULTS

Mild neonatal hyperthyrotrophinaemia represented 22·3% of patients (103/462; 60 boys, 43 girls) within our clinic. Incidence increased from two of 20 in 2000 to 31 of 74 cases in 2010. Seventy eight percent of patients started L-thyroxine (initial dose: 8·3 ± 2·5 mcg/kg). The treated group had higher confirmatory TSH levels (P = 0·001) and had undergone thyroid scintigraphy more often (P = 0·0001) compared with the nontreated group. Evidence of overtreatment was detected in 45% of thyroid function tests obtained during treatment. Among the treated infants who had reached 3 years of age, 45% (N = 14) underwent a trial-off medication. Compared with those not trialled-off therapy, these infants were less likely to have had dose escalations during treatment (P = 0·001). The trial-off treatment was successful in 50% of cases. In the subset of infants with confirmatory TSH >10 mU/l, trial-off therapy was successful in 40%. None of the assessed variables predicted success of trial-off therapy.

CONCLUSIONS

Mild neonatal hyperthyrotrophinaemia is an increasingly common diagnosis. It is more common in males and is often transient, but predictors of success of trial-off therapy were not identified. Further studies are needed to determine optimum L-thyroxine dosing and to determine whether treatment improves neurocognitive outcomes.

The role of initial clinical and laboratory findings in infants with hyperthyrotropinemia to predict transient or permanent hypothyroidism

OBJECTIVE

Studies on the clinical course of children with hyperthyrotropinemia are scarce. We aimed to evaluate the role of presentation findings in such infants to predict eventual outcome.

METHODS

Files of infants diagnosed as suspicious congenital hypothyroidism (CH) in the neonatal or early infancy period in the past ten years were analyzed retrospectively, and 37 patients (M/F: 20/17) with hyperthyrotropinemia diagnosed at a median age of 3.2 months were included in the study. Criteria for inclusion were: normal free thyroxine (fT4) levels and thyrotropin (TSH) levels between 10-20 μIU/mL during the initial neonatal screening (or TSH<10μIU/mL afterwards). Cases with permanent CH (Group 1) were compared to those with transient hyperthyrotropinemia (Group 2) regarding age at the time of diagnosis, sex, gestational age, birth weight, symptoms, ultrasonographic and scintigraphic findings, initial thyroid function tests, and state of mental and motor development.

RESULTS

Of the total group, 20 patients (54%) were eventually diagnosed as permanent CH. T4 doses that maintained normal thyroid function tests were significantly higher at the end of the first and second years of life in this group. Age, TSH and fT4 levels at the time of diagnosis, sex, gestational age, birth weight, symptoms, ultrasonographic and scintigraphic findings, and the state of mental and motor development were similar in the two groups.

CONCLUSIONS

T4 dose required to maintain a euthyroid state was the only parameter which distinguished between transient and permanent CH.

Performance metrics after changes in screening protocol for congenital hypothyroidism

OBJECTIVE

To evaluate Michigan newborn screening for congenital hypothyroidism (CH) protocol changes.

METHODS

This population-based study includes infants born and screened in Michigan (January 1, 1994-June 30, 2010). Screening performance is compared across 4 periods defined by the dried blood spot testing method: (1) thyroxine (T4) with backup thyrotropin, (2) tandem T4 and thyrotropin, (3) primary thyrotropin testing without serial testing, and (4) primary thyrotropin plus serial testing for births weighing <1800 g. Logistic regression is used to test for differences across periods.

RESULTS

Thyrotropin testing exhibited greater specificity overall and greater likelihood of detection with serial testing relative to primary T4 testing. Tandem T4 and thyrotropin testing appeared more sensitive relative to other protocols, yet it produced significantly more false-positives, and detection may have been affected by overdiagnosis and misclassification. Central CH was no longer detected once T4 testing ceased.

CONCLUSIONS

Primary thyrotropin plus serial testing for infants at risk for later rising thyrotropin outperformed other newborn screening strategies for classic CH, although 2 false-negatives occurred among normal birth weight infants admitted to the NICU during this testing period. Tandem T4 and thyrotropin screening outperformed other strategies for detection of both classic and central CH combined, although it is associated with increased operating costs. Additional research is necessary to weigh the benefits of increased sensitivity against additional program operating costs.

Thyroid dysfunctions in children detected in mass screening for congenital hypothyroidism

BACKGROUND

Congenital hypothyroidism (CH) affects approximately 1:3000-1:4000 infants.

OBJECTIVES

To determine the prevalence of CH and isolated hyperthyrotropinemia (IHT) in newborns selected in mass screening for CH.

METHODS

Mass screening of 233,120 neonates born in southeastern Poland was carried out and CH-suspected children were identified. Serum thyroid-stimulating hormone and free thyroxine levels were determined during first confirmation and diagnosis re-evaluation in 118 and 34 children, respectively. Additionally, the patients were subjected to thyroid ultrasonography (n=53) and/or scintiscan (n=28).

RESULTS

Out of 118 children, first confirmation indicated CH in 58 neonates and IHT in 4 neonates. Out of these, 34 were re-evaluated with regard to diagnosis. A final diagnosis of permanent CH was reported in 34 children with thyroid dysgenesis (n=27) or dyshormonogenesis (n=7), transient CH affected 15 children, and permanent IHT was diagnosed in 6 children. CH prevalence was 1:4570 (permanent 1:6475, transient 1:38,853) and permanent IHT 1:38,853.

CONCLUSIONS

The prevalence of CH and IHT corresponds to the prevalence of the condition in iodine-sufficient and borderline iodine-deficient areas.

Neonatal hyperthyrotropinemia: population characteristics, diagnosis, management and outcome after cessation of therapy

INTRODUCTION

Neonatal hyperthyrotropinaemia (HT), defined by elevated TSH and normal T(4), is either transient or persistent. The eventual outcome of neonatal HT is unpredictable and the management of HT patients is controversial. We assessed perinatal parameters and diagnostic measures that may distinguish between transient and persistent HT, compared with congenital hypothyroidism (CH). We also aimed to recommend optimal treatment in these forms of thyroid impairment.

DESIGN AND PATIENTS

A multi-centre, retrospective study was conducted in six paediatric endocrinology units. Forty-three HT patients and 83 CH patients were included in the study. Measurements We evaluated differences in birth weight (BW), gestational age (GA), modes of diagnosis, screening and confirmatory T(4) and TSH levels, thyroid imaging results and optimal thyroxine doses between HT and CH and between the two forms of HT.

RESULTS

Newborns with HT had lower BW and GA than those with CH. Transient (n = 18) and persistent HT (n = 25) patients were indistinguishable by most parameters, but those with persistent HT had a higher prevalence of abnormal thyroid imaging (69%vs 8%; P = 0.005). During treatment, 79% and 55% of transient and persistent HT patients respectively experienced elevated levels of free T(4.) Although most HT patients were reevaluated after 2.5 years, six transient HT patients stopped therapy and showed full recovery within the first year of life.

CONCLUSIONS

We recommend obtaining thyroid imaging to distinguish between the two forms of HT. Adherence to recommended doses of thyroxine and probably early cessation of therapy in transient HT can prevent iatrogenic hyperthyroidism in these patients.