Influence of timing and dose of thyroid hormone replacement on development in infants with congenital hypothyroidism

Analysis of motor, cognitive and language performance of infants undergoing treatment for congenital hypothyroidism

OBJECTIVE

Investigate the association between the age of treatment onset and confirmatory TSH level (as an indicator of severity) with a greater risk of developmental delay in infants with congenital hypothyroidism (CH).

METHOD

The authors conducted a cross-sectional, observational, unmatched case-control study at a Brazilian neonatal screening reference center. Seventy-seven infants with CH (mean age: 12 ± 6.4 months) were examined. The authors evaluated their performance using the Bayley-III Screening Test and categorized them as "LOWER RISK" (competent category) or "GREATER RISK" (combined at-risk + emergent categories) for developmental delay based on the 25th percentile cutoff.

RESULTS

Infants with CH are at a higher risk of non-competent performance in cognition, receptive language, fine motor skills, and gross motor skills when compared to infants without CH. This risk is more pronounced in infants with more severe indications of CH (TSH > 30 μUI/L in the confirmatory test) for cognition (OR = 5.64; p = 0.01), receptive language (OR = 14.68; p = 0.000), fine motor skills (OR = 8.25; p = 0.000), and gross motor skills (OR = 5.00; p = 0.011).

CONCLUSION

The level of TSH in the confirmatory test can be a good indicator for identifying infants with CH who are at a higher risk of non-competent performance in cognition, receptive language, and motor skills. Monitoring development, early detection of delays, and intervention programs are particularly important for infants with CH.

Assessment of Neurodevelopment and Growth in Congenital Hypothyroidism: Serial 6-Year Follow-up Study of 408 Patients

CONTEXT

The link between congenital hypothyroidism (CH) and neurodevelopment is suggested, yet studies applying quantifiable measures are lacking. Moreover, socioeconomic disparities and subtle variation in timing of approach make the relationship difficult to detect.

OBJECTIVE

To evaluate associations between CH and abnormalities in neurodevelopment and growth and determine the critical period for intervention.

METHODS

We utilized a nationwide database to conduct a longitudinal analysis of 919 707 children. Exposure to CH was identified using claims-based data. The primary outcome of interest was suspected neurodevelopmental disorder, as measured using the Korean Ages & Stages Questionnaires (K-ASQ) administered annually from 9 to 72 months of age. Secondary outcomes were height and BMI z-scores. After randomly matching cases and controls at a 1:10 ratio, we employed inverse probability of treatment weighting and generalized estimating equation models for our analyses. We conducted subgroup analysis based on the age of treatment initiation.

RESULTS

The prevalence of CH in our population was 0.05% (n = 408). Relative to the control group, the CH group had higher risk of suspected neurodevelopmental disorders (propensity score-weighted odds ratio: 4.52; 95% CI: 2.91, 7.02), and significantly increased risk in each of the 5 K-ASQ domains. No time interactions were noted at any rounds for the outcomes according to when the neurodevelopmental assessment was conducted (all P for interaction >.05). The CH group also had higher risk for low height-for-age z-score, but not for elevated BMI-for-age z-score. In subgroup analysis, delayed medication for CH correlated with worse neurodevelopmental outcomes.

CONCLUSION

The CH group had worse neurodevelopmental outcomes and reduced height-for-age z-score. Outcomes were worse when onset of treatment was increasingly delayed.

Primary congenital hypothyroidism: challenges in a low-income country without paediatric endocrinologist and universal newborn screening

Due to the lack of public awareness, congenital hypothyroidism (CH) remains an overlooked challenge in Cambodia. This disease should be screened routinely at birth because, though asymptomatic, it can lead to mental retardation in the absence of early treatment. Since 2013, our unit has been the only centre that implements routine screening and provides treatment and follow-up. This case report highlights a long and tough journey of a girl who, after being diagnosed by routine newborn screening, came for follow-up at our centre. Since the screening has yet to be recognised nationally, we want to raise not only awareness of CH but also the difficulties faced by parents because their children are in need of life-long treatment in a low-resource country. Thus, the key to successful management of paediatric patients is their parental involvement, which can be influenced by their educational, cultural, geographical and financial background.

Knowns and unknowns about congenital hypothyroidism: 2022 update

Several excellent guidelines and expert opinions on congenital hypothyroidism (CH) are currently available. Nonetheless, these guidelines do not address several issues related to CH in detail. In this review, the authors chose the following seven clinical issues that they felt were especially deserving of closer scrutiny in the hope that drawing attention to them through discussion would help pediatric endocrinologists and promote further interest in the treatment of CH. 1. How high should the levothyroxine (L-T4) dose be for initial treatment of severe and permanent CH? 2. What is the optimal method for monitoring treatment of severe CH? 3. At what level does maternal iodine intake during pregnancy affect fetal and neonatal thyroid function? 4. Does serum thyroglobulin differ between patients with a dual oxidase 2 (DUOX2) variants and those with excess iodine? 5. Who qualifies for a genetic diagnosis? 6. What is the best index for distinguishing transient and permanent CH? 7. Is there any cancer risk associated with CH? The authors discussed these topics and jointly edited the manuscript to improve the understanding of CH and related issues.

Impact of the reduction in TSH cutoff level to 6 mIU/L in neonatal screening for congenital hypothyroidism in Santa Catarina: final results

OBJECTIVE

To assess the implications of changing the cutoff level of TSH from 10 to 6 mIU/L.

METHODS

The study population was constituted by 74.123 children screened for congenital hypothyroidism by the National Screening Program in Santa Catarina, from March 2011 to February 2012. The cutoff of TSH was 6 mIU/L. If TSH between 6-10 mIU/L, the newborn was recalled for a second TSH measurement on filter paper. If TSH > 6 mIU/L in the second sample, the child was sent for medical evaluation. In children with normal topic thyroid, levothyroxine was suspended for 1 month at the age of 3 years for identification of the etiology and evaluation of the need to continue treatment.

RESULTS

Among the children screened, 435 were recalled for presenting TSH between 6 and 10 mIU/L in the first sample, 28 remained TSH > 6 mIU/L in the second sample. Among these, 11 had a final diagnosis of dyshormonogenesis, two of ectopic thyroid, two of thyroid hypoplasia and one of transient hypothyroidism. Ten children presented normal TSH levels on the first medical evaluation and two lost follow-up.

CONCLUSION

A decrease in the TSH cutoff level from 10 to 6 mIU/L in a neonatal screening program for congenital hypothyroidism reduced the number of false-negative results, increasing the sensitivity of the test, but increased the number of false-positive results and recalls. Since a TSH cutoff level of 6 mIU/L detects thyroid function abnormalities requiring treatment, the adoption of this cutoff level is justified.

Basal Serum Thyroxine Level should Guide Initial Thyroxine Replacement Dose in Neonates with Congenital Hypothyroidism

OBJECTIVE

Initial high-dose sodium levothyroxine (Na-LT₄) (10-15 μg/kg/day) replacement for primary congenital hypothyroidism (CH) is recommended in guidelines. However, high-dose Na-LT₄ risks iatrogenic hyperthyroidism. The aim of this study was to investigate the normalizing effect of varying initial doses of Na-LT₄ on serum thyroid hormone levels.

METHODS

Fifty-two patients were analyzed retrospectively. The patients were classified into mild (27/51.9%), moderate (11/21.1%) and severe (14/26.9%) CH, based on initial free thyroxine (fT₄) levels. Time taken to achieve target hormone levels was compared within groups.

RESULTS

Initial mean Na-LT₄ doses for mild, moderate and severe disease were 6.9±3.3, 9.4±2.2 and 10.2±2 μg/kg/day. Serum fT₄ levels reached the upper half of normal range (>1.32 ng/dL) in a median of 16, 13 and 16 days in patients with mild, moderate and severe CH with the mean time from initial treatment to first control visit of 14.8±6 days (range 1-36). There was no significant difference in terms of time to achieve target fT₄ hormone levels according to disease severity (p=0.478). Seven (25.9%), eight (72.7%) and eight (57.1%) patients experienced hyperthyroxinemia (serum fT₄ >1.94 ng/dL) in the mild, moderate, and severe CH groups at the first visit, respectively (p=0.016).

CONCLUSION

Not all patients diagnosed with CH require high-dose Na-LT₄. Initial dose of Na-LT₄ may be selected on the basis of pre-treatment thyroid hormone levels. Some patients with moderate and severe CH, experienced iatrogenic hyperthyroxinemia even though the dose was close to the lower limit of the recommended range in guidelines. We suggest that lower initial doses may be appropriate with closer follow-up within the first week.

Congenital Hypothyroidism

Congenital hypothyroidism (CH) is the commonest preventable cause of mental retardation in human species. It is so important for clinician to know its etiology epidemiology, clinical manifestation and treatment strategies. Since it is one of the rare serious diseases that should not be diagnosed clinically because late clinical features corresponds to advanced mental retardation, the neonatal screening detection is the best and preferable way of early diagnosis of this congenital disease. Confirmatory laboratory and radiological diagnostic tests should be performed immediately after the positive neonatal screening test. In order to prevent mental defects and to maintain long term clinical as well as biochemical euthyroidism in affected children its diagnosis approach, medical treatment and follow-up should be well established knowledge to all pediatricians during the childhood period and later on to general practitioners when these individuals grow up as adults. Congenital hypothyroidism is a potentially serious disease that we need to emphasize on early detection, using proper diagnostic tools and early and planned therapeutic approach.

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.

Upper and Lower Limb Strength and Body Posture in Children with Congenital Hypothyroidism: An Observational Case-Control Study

BACKGROUND

Congenital hypothyroidism (CH) is an endocrine disease with a precocious significant impairment of growth and neuromotor development. Thyroid hormones are essential for central nervous system development, maturation, and myelination. Furthermore, thyroid hormone deficiency affects the function of several systems, including the musculoskeletal system. The disease has a significant incidence in the general population (1:3000-1:2000 newborns in Italy). The aim of the present study was to evaluate any differences in upper and lower limb strength, body sway, and plantar loading distribution in children with CH compared to healthy children.

METHODS

In this study, the case group was composed of children with CH (CHG), while the control group included healthy children (CG). Both groups comprised 19 children (CHG: female = 12; CG: female = 9). The maximum isometric handgrip strength and explosive-elastic lower limb strength were assessed with the handgrip test and the Sargent test, respectively. The stabilometric and baropodometric analyses were used to measure the Center of Pressure displacements and the plantar loading distribution between feet, respectively. The differences between groups were analyzed by a univariate analysis of covariance using as covariates weight and height with the significant level set at < 0.05.

RESULTS

We found that CHG children were shorter and thinner than CG ones (p < 0.05). No significant difference in the upper and lower limb strength was found between groups. CHG exhibited a significant greater Sway Path Length (p < 0.01) and Ellipse Surface (p < 0.05) than CG. Moreover, CHG displayed an asymmetric plantar loading distribution with a significant lower percentage in the right than in the left foot (p < 0.05). Moreover, a significant lower plantar loading percentage in the right foot of CHG than in the right foot of CG was observed (p < 0.05).

CONCLUSIONS

These findings seem to suggest that CH does not affect muscle strength in early treated children. However, these patients show poor postural control ability and asymmetric plantar loading distribution. Increasing the physical activity in these children could improve their body posture.

Cases Referred from the Turkish National Screening Program: Frequency of Congenital Hypothyroidism and Etiological Distribution

OBJECTIVE

The aim of this study was to evaluate cases referred from the congenital hypothyroidism (CH) newborn screening program.

METHODS

Infants referred to Pediatric Endocrinology between 30.09.2015 - 01.04.2018 because of suspected CH identified by National Neonatal Screening Program were prospectively evaluated.

RESULTS

Of the 109 newborns referred to our clinic, 60 (55%) were diagnosed with elevated neonatal thyroid stimulating hormone (TSH). The diagnosis of elevated neonatal TSH was made in 52 (47.7%) and eight (7.3%) infants at initial evaluation and after follow up, respectively of all referrals with 86.7% (52/60) diagnosed at initial visit. The median first and second heel prick times were 1.8 (0-7) and 8.72 (4-30) days. The median age at starting treatment of the infants diagnosed as a result of initial evaluation was 22.13 (7-53) days. Clinical findings associated with CH were present in 19 (36%) of patients. Etiology in patients diagnosed with elevated neonatal TSH on admission was: agenesis in one (2.08%); ectopia in one (2.08%); hypoplasia in 14 (29.16%); normal gland in situ 16 (33.3%); and hyperplasia in 16 (33.3%). The median time to normalization of TSH and free thyroxine concentrations after treatment initiation was 11.02 (4-30) and 9.03 (3-30) days, respectively.

CONCLUSION

The rate of diagnosis in the first month was found to be 87%. The etiological incidence of both dysgenesis and dyshormonogenesis was equal at 33.3%. The majority of cases with normal thyroid gland will be diagnosed with transient hypothyroidism but some of them may be diagnosed with thyroid dyshormonogenesis so the rate of dyshormonogenesis will increase later after final diagnosis.

Evaluation of the congenital hypothyroidism screening programme in Iran: a 3-year retrospective cohort study

OBJECTIVE

To evaluate the newborn screening programme for congenital hypothyroidism (CH) in Iran from diagnosis to management and follow-up for 3 years from 2011 to 2014.

DESIGN

Retrospective cohort.

SETTING AND PATIENTS

Seventeen university districts were randomly selected from 30 provinces. Central data in each district were gathered and collectively analysed. Congenital hypothyroid subjects were followed for 3 years.

MAIN OUTCOME MEASURES

Programme coverage, screening and treatment age, recall rate, compliance to follow-ups.

RESULTS

The total number of births in 2011 was 501 726, of which 452 918 neonates (90.3%) were screened and 15 671 (3.46%) were recalled; 1085 (1:462, 0.22%) were confirmed as having CH (57.1%: permanent, 42.9%: transient) and followed for 3 years. Positive predictive value (PPV) for the first screening test was 6.9%. After the second screening, recall rate was reduced to 0.69% and PPV increased to 31.3%. Median age at screening was 6 (3-9) days and for 90.6% of patients treatment was initiated before 40 days of age with a median levothyroxine dosage of 25 µg/day; 131 (13.4%) were lost to follow-up. Mean number of follow-up visits over 3 years was 5.7 (95% CI 5.5 to 5.9) and 23% (n=225) had total compliance to all follow-ups. Median time for thyroid stimulating hormone normalisation was 45 days, 95% CI (41.1 to 48.8).

CONCLUSION

In Iran, despite well-established protocols of screening and detecting CH subjects, stricter implementation of a structured system for monitoring and surveillance is needed to promote the management of patients and to reduce rates of loss to follow-up. Determining and addressing the causes of high false positive rates must be prioritised.

Características clínicas de los niños con hipotiroidismo congénito en Santander, Colombia

Introducción. El hipotiroidismo congénito (HC) es la primera causa de retraso mental prevenible. El inicio temprano de su tratamiento con la hormona tiroidea garantiza un desarrollo neurológico normal.Objetivos. Describir la etiología y las manifestaciones clínicas del HC y relacionar la discapacidad cognitiva con el inicio del tratamiento en una serie de casos de niños con esta enfermedad en el departamento de Santander, Colombia.Materiales y métodos. Estudio descriptivo a través de serie de casos. La información se recolectó de historias clínicas de pacientes con HC diagnosticado entre 1999 y 2013 y atendidos por el Servicio de Endocrinología Pediátrica del Hospital Universitario de Santander Empresa Social del Estado. Se analizaron 15 variables en el programa Microsoft Excel 2013.Resultados. Se recolectaron 59 casos, con una relación sexo femenino/masculino de 1.7:1. En el 49.2% de los casos se realizó tamizaje neonatal. Las disgenesias tiroideas fueron la etiología más común; la ictericia neonatal prolongada, la hernia umbilical y la hipotonía fueron las características más frecuentes. El retraso mental se presentó en el 64.4% de los casos.Conclusiones. El tamizaje neonatal es la mejor estrategia para captar la mayoría de los casos e iniciar tratamiento oportuno. En Colombia, la ictericia neonatal prolongada debe alertar un posible caso de HC.

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.

Relation between Early Over- and Undertreatment and Behavioural Problems in Preadolescent Children with Congenital Hypothyroidism

OBJECTIVE

Congenital hypothyroidism (CH) per se, when not treated or undertreated, may lead to severe behavioural problems (cretinism), whereas overtreatment of CH seems associated with attention problems.

DESIGN AND METHODS

For 55 CH patients, prospectively followed from birth until 11 years, parents rated the Child Behaviour Checklist and teachers the Teacher's Report Form at children's ages 6 and 11 years. We related scores regarding Attention, Delinquency, and Aggression (ADA scores, indicative for attention deficit hyperactivity syndrome, ADHD), and scores regarding Withdrawn, Anxious, Social, and Thought problems (WAST scores, indicative for autism) to the occurrence of over- and undertreatment in five age periods. Over- and undertreatment were defined as free thyroxine (fT4) concentrations above/below the range of the patient's individual fT4 steady state concentration.

RESULTS

ADA scores at 6 and 11 years for patients overtreated in the period 1-3 months postnatally were higher than those for patients who were not overtreated. Patients with severe CH undertreated in the period 3-6 months postnatally had higher WAST scores at 6 and 11 years than all other patients.

CONCLUSIONS

This is the first study suggesting that permanent ADHD as well as autism in CH patients at ages 6 and 11 years are the result of early overtreatment and undertreatment, respectively.

Current status of the congenital hypothyroidism neonatal screening program in Adana Province, Turkey

BACKGROUND

Congenital hypothyroidism (CH) is a common cause of mental retardation; it has a worldwide incidence ranging from 1:3000 to 1:4500 live births. Predictably, an increase in the reported incidence of primary CH occurs when the cut-off levels of thyroid-stimulating hormone are lowered. We aimed to evaluate the results of a congenital hypothyroidism screening program and current status in this study.

METHODS

Analysis results of 1300 infants who were referred to the endocrinology polyclinic because of suspected CH within the scope of the Ministry of Health National Neonatal Screening Program were retrospectively evaluated.

RESULTS

The diagnosis of CH and initiation of treatment were both done in 223 (18.5%) and 10 (0.8%) infants as a result of the initial evaluation and follow-up, respectively. The mean capillary and venous thyroid-stimulating hormone (TSH) levels of 223 patients were 40.78 (5.5-100) μIU/mL and 67.26 (10.7-100) μIU/mL, respectively. These patients' mean heel prick time was 8.65 (0-30, median: 7) days. The mean age of the 223 infants whose treatment was initiated as a result of the initial evaluation was 19.87 (4-51, median: 20) days, and the mean age of the infants whose treatment was started at follow-up was 43.71 (29-65) days. The duration between heel prick time and venous TSH time was 11.10 (2-28, median: 11) days and was longer than planned (3-5 days).

CONCLUSIONS

Although the duration for the diagnosis and initiation of CH treatment were markedly reduced with the implementation of the screening program in Turkey compared to those before the implementation of the screening program, we have not yet achieved the ideal time (≤14 days).

Congenital Hypothyroidism

Congenital hypothyroidism is common and can cause severe neurodevelopmental morbidity. Prompt diagnosis and treatment are critical to optimizing long-term outcomes. Universal newborn screening is an important tool for detecting congenital hypothyroidism, but awareness of its limitations, repeated screening in high-risk infants, and a high index of clinical suspicion are needed to ensure that all affected infants are appropriately identified and treated. Careful evaluation will usually reveal the etiology of congenital hypothyroidism, which may inform treatment and prognosis. Early and adequate treatment with levothyroxine results in excellent neurodevelopmental outcomes for most patients with congenital hypothyroidism.

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.

Individualized treatment to optimize eventual cognitive outcome in congenital hypothyroidism

BACKGROUND

In congenital hypothyroidism (CH), age-specific reference ranges (asRR) for fT₄ and thyrotropine (TSH) are usually used to signal over/under-treatment. We compared the consequences of individual fT₄ steady-state concentrations (SSC's) and asRR regarding over-treatment signaling and intelligence quotient at 11 y (IQ₁₁) and the effect of early over-treatment with high L-T₄ dosages on IQ₁₁.

METHODS

Sixty-one patients (27 severe, 34 mild CH) were psychologically tested at 1.8, 6, and 11 y. Development scores were related to over-treatment in the period 0-24 mo, relative to either individual fT₄SSC's or asRR. Three groups were formed, based on severity of over/under-treatment 0-5 mo (severe, mild, and no over/under-treatment).

RESULTS

FT₄ and TSH asRR missed 41-50% of the over-treatment episodes and consequently 22% of the over-treated patients, classified as such by fT₄SSC's. Severe over-treatment 0-5 mo led to lowered IQ₁₁'s and to a 5.5-fold higher risk of IQ₁₁ < 85 than other treatment regimes. Under-treatment had no effect on development scores. Initial L-T₄ dosages >10 µg/kg resulted in a 3.7-fold higher risk of over-treatment than lower dosages.

CONCLUSIONS

Data suggest that asRR, compared to fT₄SSC's, signal over-treatment insufficiently. Using fT₄SSC's and avoiding over-treatment may optimize cognitive outcome. Lowered IQ₁₁'s are usually a late complication of severe early over-treatment.

Liothyronine Improves Biochemical Control of Congenital Hypothyroidism in Patients with Central Resistance to Thyroid Hormone

OBJECTIVE

To assess whether adding liothyronine (LT3) to levothyroxine (LT4) monotherapy normalizes serum thyrotropin (TSH) and thyroxine (T4) concentrations in children with congenital hypothyroidism and central resistance to thyroid hormone.

STUDY DESIGN

We retrospectively studied 12 patients with congenital hypothyroidism and central resistance to thyroid hormone (6 treated with LT3+LT4 combined therapy and 6 treated with LT4 monotherapy). In patients receiving combined therapy, we compared serum concentrations of TSH, T4, and triiodothyronine before and after addition of LT3. We used repeated measures analysis to compare thyroid function in participants receiving combined therapy vs monotherapy, while accounting for age and intrasubject correlation.

RESULTS

In patients receiving combined therapy, the addition of LT3 was associated with normalization of mean TSH (9.2 vs 4.5 mIU/L, P = .002), a lower proportion of TSH values greater than 10 mIU/L (35% vs 8%, P = .03), and a decrease in mean serum T4 by 23 ± 9% (P < .001). Compared with patients receiving LT4 monotherapy, patients receiving combined therapy had lower mean TSH (8.5 ± 0.9 vs 4.3 ± 0.4, P < .001), lower odds of TSH elevation greater than 10 mIU/L (OR 0.20, 95% CI 0.10-0.41, P < .001), and lower odds of T4 elevation (OR 0.21, 95% CI 0.04-1.09, P = .06). LT3 treatment did not increase serum T3 levels significantly.

CONCLUSION

The addition of LT3 to LT4 monotherapy facilitates normalization of both serum TSH and T4 in patients with congenital hypothyroidism and central resistance to thyroid hormone. Larger prospective studies are needed to confirm these findings and to determine the effect of combined therapy on neurodevelopmental outcomes.

Congenital Hypothyroidism: Optimal Initial Dosage and Time of Initiation of Treatment: A Systematic Review

CONTEXT

Appropriate management of neonates, tested positive for congenital hypothyroidism (CH), in particular, the initial dosage of levothyroxine and the time of initiation of treatment is a critical issue. The aim of this study was to assess all current evidence available on the subject to ascertain the optimal initial dose and optimal initiation time of treatment for children with CH.

EVIDENCE ACQUISITION

In this study, all published research related to the initiation treatment dose and the onset time of treatment in congenital hypothyroidism were reviewed. The searched electronic databases included Medline, Science direct, Scopus EMBASE, PsycINFO, Cochrane, BIOSIS and ISI Web of Knowledge. Additional searches included websites of relevant organizations, reference lists of included studies, and issues of major thyroid and pediatrics journals published within the past 35 years. Studies were included if they were written in English and investigated levothyroxine dose or timing of treatment or both, used for the treatment of children with congenital hypothyroidism.

RESULTS

Two thousand three hundred and seventy-four articles (excluding duplicates) were retrieved from the primary search. After reviewing the titles, abstracts and full-texts of studies, eventually, 22 studies were found that met our inclusion criteria. Amongst these, 17 and 12 evaluated outcomes of different treatment doses and treatment timing, respectively. Overall, the majority of these studies emphasized the initial high dose of levothyroxine and early treatment of newborns with hypothyroidism. There were, however, some studies that disagreed with increasing levothyroxine dose at initiation of treatment.

CONCLUSIONS

Considering the results of this review, apparently there is no difference in opinion regarding the early initiation of treatment, whereas determining the optimal dose of levothyroxine for start of treatment in CH patients still remains a controversial issue, demonstrating the need for further studies, despite the fact that use of high doses can lead to rapid normalization of biochemical indices, although this may cause complications.

The role of ¹²³I imaging in the evaluation of infants with mild congenital hypothyroidism

BACKGROUND/AIMS

Controversy exists regarding the diagnosis and treatment of mild congenital hypothyroidism (MCH). We studied the value of (123)I imaging in patients with MCH.

METHODS

Retrospective chart review of infants and children <4 years of age who underwent (123)I imaging: group 1 = MCH [thyroid-stimulating hormone (TSH) <25 µIU/ml, normal free T4/T3], group 2 = severe congenital hypothyroidism (TSH ≥25 µIU/ml), and group 3 = MCH in infancy imaged after treatment withdrawal at age 3 years. Data collected included 4- and 24-hour (123)I uptake, TSH, free T4/total T3 at imaging, age at imaging, and levothyroxine (L-T4) dose at 1 year of.

RESULTS

Thirty-six patients underwent (123)I imaging. In group 1 (n = 20, median TSH: 8.49 µIU/ml), 85% had abnormal imaging consistent with dyshormonogenesis. Two patients were referred after 1 year of age. The median age at imaging for the remaining 18 patients was 54 days. Median L-T4 dose at 1 year of age for these 18 patients was 2.8 μg/kg, which is consistent with dyshormonogenesis. Ninety-one percent of group 2 (n = 11, median TSH: 428.03 µIU/ml) had abnormal imaging. The median age at imaging was 13 days. Four patients in group 3 had abnormal (123)I imaging and restarted treatment.

CONCLUSION

(123)I imaging is a valuable tool for evaluation, diagnosis, and treatment of MCH.

Daily versus alternate day thyroxine therapy to maintain euthyroidism in children with congenital hypothyroidism

BACKGROUND

Daily administration of thyroxine has proven efficacy in treatment of children with hypothyroidism. However, the possibility of treatment with longer dosing intervals that offers flexibility and choice in maintaining euthyroid state has not been tested in children.

OBJECTIVES

To study the efficacy of an alternate day regimen to maintain euthyroidism in children with congenital hypothyroidism.

PATIENTS AND METHODS

Forty patients given alternate day therapy, while 30 children continued on their daily regimen were followed up at monthly intervals for 3 months. Clinical and laboratory assessments were performed at each follow up visit.

RESULTS

The clinical and anthropometric parameters remained similar in both groups of patients during the study indicating a maintained euthyroid state clinically. The thyroid profiles also remained within normal limits suggesting biochemical euthyroidism status with alternate day therapy. However the baseline serum aminotransferase levels showed mild elevation in patients on alternate day regimen and the difference persisted during the follow up visits. Higher HDL and lower TC and LDL levels suggested some beneficial effect of alternate day schedule on lipid profiles.

CONCLUSIONS

In short-term, alternate day schedule can be effectively used to maintain clinical and biochemical euthyroid state in children with congenital hypothyroidism beyond 4 years of age.

Iodine and mental development of children 5 years old and under: a systematic review and meta-analysis

Several reviews and meta-analyses have examined the effects of iodine on mental development. None focused on young children, so they were incomplete in summarizing the effects on this important age group. The current systematic review therefore examined the relationship between iodine and mental development of children 5 years old and under. A systematic review of articles using Medline (1980-November 2011) was carried out. We organized studies according to four designs: (1) randomized controlled trial with iodine supplementation of mothers; (2) non-randomized trial with iodine supplementation of mothers and/or infants; (3) prospective cohort study stratified by pregnant women's iodine status; (4) prospective cohort study stratified by newborn iodine status. Average effect sizes for these four designs were 0.68 (2 RCT studies), 0.46 (8 non-RCT studies), 0.52 (9 cohort stratified by mothers' iodine status), and 0.54 (4 cohort stratified by infants' iodine status). This translates into 6.9 to 10.2 IQ points lower in iodine deficient children compared with iodine replete children. Thus, regardless of study design, iodine deficiency had a substantial impact on mental development. Methodological concerns included weak study designs, the omission of important confounders, small sample sizes, the lack of cluster analyses, and the lack of separate analyses of verbal and non-verbal subtests. Quantifying more precisely the contribution of iodine deficiency to delayed mental development in young children requires more well-designed randomized controlled trials, including ones on the role of iodized salt.

Hipotireoidismo congênito: recomendações do Departamento de Tireoide da Sociedade Brasileira de Endocrinologia e Metabologia

O hipotireoidismo congênito (HC) é o distúrbio endócrino congênito mais frequente, com incidência variando de 1:2.000 a 1:4.000 crianças nascidas vivas e uma das principais causas de retardo mental que pode ser prevenida. Os Programas de Triagem Neonatal para a doença permitem a identificação precoce dos afetados e seu tratamento de modo a evitar as complicações da falta do hormônio. A maioria dos casos de hipotireoidismo congênito é decorrente de disgenesias tireoidianas (85%), entre elas a ectopia, hipoplasia ou agenesia tireoidianas, e os demais resultam de defeitos de síntese hormonal. As crianças afetadas (> 95%) geralmente não apresentam sintomas sugestivos da doença ao nascimento. Os sintomas e sinais mais comuns são: icterícia neonatal prolongada, choro rouco, letargia, movimentos lentos, constipação, macroglossia, hérnia umbilical, fontanelas amplas, hipotonia e pele seca. Várias estratégias são utilizadas para a triagem do HC. No Brasil, esta é obrigatória por lei e geralmente é feita com a dosagem de TSH em sangue seco coletado do calcanhar. A idade recomendada para sua realização é após as 48 horas de vida até o quarto dia. A confirmação diagnóstica é obrigatória com as dosagens de TSH e T4 livre ou T4 total.

The Italian screening program for primary congenital hypothyroidism: actions to improve screening, diagnosis, follow-up, and surveillance

The Italian screening program for primary congenital hypothyroidism (CH) is an integrated system including neonatal screening, diagnosis, treatment, follow-up, and nationwide surveillance of the disease. The aim of the Italian screening program for CH is to identify not only babies with severe permanent CH (core target), but also babies with mild persistent and transient forms of CH who could have a benefit from an early replacement therapy (secondary target). In the last years, despite the important results obtained in terms of standardization of screening and follow-up procedures, it has become clear the need of optimizing the program in order to harmonize the screening strategy and the screening procedures among Regions, and to improve the diagnostic and therapeutic approach in all affected infants. On the basis of available guidelines, the experience of the Italian screening and clinical reference centers, and the knowledge derived from the nation-wide surveillance activity performed by the Italian National Registry of Infants with CH, the Italian Society for Pediatric Endocrinology and Diabetology together with the Italian Society for the Study of Metabolic Diseases and Neonatal Screening and the Italian National Institute of Health promoted actions aimed at improving diagnosis, treatment, follow-up and surveillance of CH in our country. In this paper the most important actions to improve the Italian screening program for CH are described.

Growth and specialized growth charts of children with congenital hypothyroidism detected by neonatal screening in isfahan, iran

Objectives. The aim of the current study was to investigate the growth status of CH, generate specialized growth charts of CH infants, and compare them with their counterparts of regional normal infants. Methods. In this prospective cohort study, 760 (345 girls and 415 boys) neonates born in 2002-2009 diagnosed by neonatal CH screening program in Isfahan were followed up from the time of diagnosis. 552 healthy children were recruited as a control group. The empirical 3rd, 15th, 50th, 85th, and 97th percentiles for height, weight, and head circumference of both sexes were determined and compared with their counterpart values of the control group. The relative frequency of patients with impaired growth for each studied variable was determined. Also, specialized growth charts of CH patients were generated. Results. The percentiles of weight, height, and head circumference of studied patients are significantly different from regional healthy children (P < 0.001). The relative frequency of impaired head circumference was decreased to less than 3% at the 3rd year of age and for height it reached gradually 3% and 9% at the 5th year of age for boys and girls, respectively (P < 0.05); however for weight still it was statistically more than 3% in both sexes. Conclusion. CH patients had impaired growth development which was improved during follow up, but the catch-up time was earlier for head circumference and later for weight.

Avaliação do valor de corte de TSH em amostras de filtro na triagem neonatal para diagnóstico de hipotireoidismo congênito no Programa "Primeiros Passos" - IEDE/RJ

OBJETIVO: Analisar casos de hipotireoidismo congênito (HC) confirmados ou não, triados pelo Programa "Primeiros Passos", estratificando-os em faixas de TSH em filtro (TSH-F). MATERIAIS E MÉTODOS: Estratificar, em faixas de TSH-F em função do TSH em soro (TSH-S), os casos convocados para teste confirmatório de janeiro/2006 a julho/2009. RESULTADOS: Cerca de 37% dos casos confirmados (475) apresentaram TSH-F > 9,5 mUi/L, mas a maioria dos casos confirmados estava nas faixas de TSH-F mais baixas. Entre os casos não confirmados (4.613), a maior parte se encontrava nas faixas mais baixas. Não houve faixa de TSH-F exclusiva dos casos não confirmados. CONCLUSÃO: O valor de corte do TSH-F utilizado é fundamental no diagnóstico do HC e deve ser baixo, mesmo que sejam realizados mais testes confirmatórios. Mais estudos são necessários para determinar o melhor valor de corte de TSH-F para triagem neonatal.

Generic and brand-name L-thyroxine are not bioequivalent for children with severe congenital hypothyroidism

CONTEXT

In the United States, generic substitution of levothyroxine (L-T(4)) by pharmacists is permitted if the formulations are deemed to be bioequivalent by the Federal Drug Administration, but there is widespread concern that the pharmacokinetic standard used is too insensitive.

OBJECTIVE

We aimed to evaluate the bioequivalence of a brand-name L-T(4) (Synthroid) and an AB-rated generic formulation (Sandoz, Princeton, NJ) in children with severe hypothyroidism.

DESIGN

This was a prospective randomized crossover study in which patients received 8 weeks of one L-T(4) formulation followed by 8 weeks of the other.

SETTING

The setting was an academic medical center.

PATIENTS

Of 31 children with an initial serum TSH concentration >100 mU/L, 20 had congenital hypothyroidism (CH), and 11 had autoimmune thyroiditis.

MAIN OUTCOME MEASURES

The primary endpoint was the serum TSH concentration. Secondary endpoints were the free T(4) and total T(3) concentrations.

RESULTS

The serum TSH concentration was significantly lower after 8 weeks of Synthroid than after generic drug (P = .002), but thyroid hormone levels did not differ significantly. Subgroup analysis revealed that the difference in TSH was restricted to patients with CH (P = .0005). Patients with CH required a higher L-T(4) dose (P < .0004) and were younger (P = .003) but were not resistant to thyroid hormone; 15 of 16 CH patients had severe thyroid dysgenesis or agenesis on imaging. The response to generic vs brand-name preparation remained significant when adjusted for age.

CONCLUSIONS

Synthroid and an AB-rated generic L-T(4) are not bioequivalent for patients with severe hypothyroidism due to CH, probably because of diminished thyroid reserve. It would therefore seem prudent not to substitute L-T(4) formulations in patients with severe CH, particularly in those <3 yr of age. Our results may have important implications for other severely hypothyroid patients in whom precise titration of L-T(4) is necessary.

Experience in treating congenital hypothyroidism: implications regarding free thyroxine and thyrotropin steady-state concentrations during optimal levothyroxine treatment

BACKGROUND

A major problem in the treatment of patients with congenital hypothyroidism (CHT) is that the optimal individual target values of thyrotropin (TSH) and free thyroxine (fT(4)) are unknown. We investigated whether patients with CHT have during treatment considered optimal stable fT(4) and TSH steady-state concentrations (SSCs) that can be used as target values, and whether TSH or fT(4) is more useful in guiding decisions regarding therapy.

METHODS

From 60 early-treated patients with CHT, TSH and fT(4) follow-up samples within the age interval 1.5-132 months (postinitial period) and within TSH interval 0.5-10 mU/L were selected. TSH and fT(4) SSCs were estimated by taking the individual mean values of a series of determinations, under the most euthyroid conditions possible (n=1257), for the whole age and TSH intervals, as well as for the age intervals 1.5-24, 25-72, and 73-132 months, as well as, for fT(4), for the two split TSH intervals 0.5-4.49 and 4.5-10 mU/L. For all SSCs, the within-subject coefficient of variation (CV(w)) was determined. Further, fT(4) SSCs were assessed for the first 6 weeks after therapy initiation.

RESULTS

For both TSH and fT(4), individual SSCs differed significantly (p<0.001). The 95% confidence interval for TSH SSCs was 1.1-5.7 mU/L and for fT(4) SSCs 16.6-28.7 pmol/L. Mean CV(w) values for TSH and fT(4) SSCs were 60.9% and 13.1%, respectively. Individual fT(4) and TSH SSCs were reproducible when assessed for the three age intervals, both slightly decreasing with age (p≤0.033), and fT(4) SSCs were reproducible for the two split TSH intervals, with a slight fT(4) difference (p<0.001). fT(4) SSCs were largely independent of the administered LT(4) dosage (range 2.4-6.1 μg/kg). fT(4) SSCs of the initial period were comparable to those of postinitial period with a mean±SD difference of 1.0±3.5 pmol/L, p=0.07.

CONCLUSIONS

Our study suggests that in CHT during therapy considered optimal, stable TSH and fT(4) SSCs can be found slightly decreasing with age and largely independent of the administered LT(4) dosage (range 2.4-6.1 μg/kg). In clinical follow-up, fT(4) SSCs may be more valuable as individual target values than TSH SSCs.

Diagnosed congenital hypothyroidism with missing follow-up: is it time for a national registry?

A treatable and preventable disorder, congenital hypothyroidism (CH) is still a common cause of mental retardation. A 17-year-old Saudi boy with CH due to an ectopic thyroid gland was diagnosed by the neonatal screening program.Thyroxine replacement therapy was started for one month when the family chose to discontinue medication and follow-up. He was not then seen until 11 years of age. Thyroxine was restarted with a close follow-up, although thyroid function tests gradually improved back to normal levels, but his final height was short (159 cm) and IQ was negatively affected. Despite the diagnosis having been made at an appropriate time, patient was lost to follow up. This indicates an obvious flaw in the system for follow-up care. We recommend a registry of patients with CH to monitor their care. The aim of such a registry would be to monitor the efficiency and efficacy of neonatal screening.

Evaluation of cognitive and motor development in toddlers with congenital hypothyroidism diagnosed by neonatal screening

OBJECTIVE

The Dutch neonatal congenital hypothyroidism (CH) screening procedure and treatment modality has been adapted several times since its national institution in 1981. These changes enabled us to investigate whether earlier treatment has resulted in improved cognitive and motor outcomes. The present study examined whether the advancement of treatment modality has resulted in improved cognitive and motor outcomes.

METHODS

In 95 toddlers with thyroidal CH (CH-T), born in 2002 through 2004 and treated at a median age of 9 days, cognitive and motor outcomes were assessed with the Bayley Scales of Infant Development-II-NL at 1 and 2 years of age. This outcome was also analyzed in relation to treatment variables.

RESULTS

The mean mental developmental index (MDI) scores of the severe (initial free thyroxine [FT4] ≤0.4 ng/dL (≤5 pmol/L), moderate (0.4 < initial FT4 ≤ 0.8 ng/dL (5.0 < initial FT4 ≤ 10.0 pmol/L), and mild (initial FT4 > 0.8 ng/dL (>10.0 pmol/l) CH-T groups at 1 year and the moderate and mild CH-T groups at 2 years were similar to the population mean. The mean MDI scores of the total CH-T group and severe CH-T group at 2 years were significantly lower than the population mean (p < .0001). In all 3 severity subgroups, significant lower psychomotor developmental index scores (p < .0001) were observed. No correlations were found between starting day of treatment and developmental outcome. Initial T4 concentration and initial T4 dose were weak predictors for developmental outcome.

CONCLUSION

Essentially, comparable with our earlier findings, children with CH, especially those with severe CH, are still at risk for motor and cognitive problems, which are probably due to the consequence of the prenatal hypothyroid state or the thyroid hormone deficiency in early life.

Newborn thyroid-stimulating hormone in children with optic nerve hypoplasia: associations with hypothyroidism and vision

PURPOSE

To assess in children with optic nerve hypoplasia (ONH) whether newborn screening (NBS) thyroid-stimulating hormone (TSH) measurements can detect central hypothyroidism and whether newborn TSH or subsequent thyroidal status is associated with visual function.

METHODS

From a registry of children with ONH at Children's Hospital Los Angeles, post-natal thyroidal status was retrospectively compared with NBS TSH levels in the subset of subjects born in California. The subset of subjects with outcome data at age 5 years was assessed for relationship of vision to NBS TSH levels and ultimate thyroidal status.

RESULTS

A total of 135 subjects from the ONH registry were included in this study. Approximately 50% of subjects in each analysis were hypothyroid. Those diagnosed with hypothyroidism had lower median NBS TSH levels than did euthyroid subjects (3.2 vs 4.5 μIU/mL; P = 0.006) and significantly worse quantitative vision outcomes (median visual acuity, logMAR 3.0 vs 1.0; P = 0.039). Receiver operating characteristic analysis suggested an optimal NBS TSH cut-point of 3.3 μIU/mL. Serum TSH levels greater than this (30/43) were associated with relatively better vision outcomes (median visual acuity, logMAR 1.2 vs 3.3; P = 0.04).

CONCLUSIONS

Children with ONH and lower NBS TSH levels are more likely to have central hypothyroidism and less likely to experience good vision than those with greater NBS TSH levels.

Effect of Prolonged Discontinuation of L-Thyroxine Replacement in a Child with Congenital Hypothyroidism

When diagnosed through neonatal screening and treated promptly and adequately, infants with congenital hypothyroidism (CH) experience normal physical growth and neurological development. Here we present a 3-year-old boy diagnosed with CH as a newborn, who was subsequently left untreated and experienced significant growth failure and developmental delay. This case emphasizes the importance of a consistent adherence to treatment in preventing such complications, especially in infancy and early childhood.

Situação atual da triagem neonatal para hipotireoidismo congênito: críticas e perspectivas

O hipotireoidismo congênito (HC) é uma das causas mais frequentes de deficiência mental passível de prevenção. Esforços devem ser utilizados na sua detecção e no tratamento precoces. O atraso no diagnóstico e no tratamento resultará em sequela neurocognitiva. A triagem neonatal mudou a evolução natural dessa enfermidade. O nível de corte do TSH utilizado é 10 mUI/l. No Brasil, a triagem neonatal é realizada há três décadas. Atualmente todos os estados brasileiros e o Distrito Federal a realizam. Analisando os últimos dados do Programa Nacional de Triagem Neonatal (PNTN), observamos que existe uma diferença enorme entre os Serviços de Referência nos vários estados. A cobertura do PNTN é de 81,61% dos recém-nascidos. Apenas 56,94% colheram a amostra até sete dias de vida. Os tempos médios da coleta até a chegada da amostra ao laboratório, da realização da dosagem do TSH, da liberação do resultado e reconvocação das crianças suspeitas estão fora do preconizado, culminando numa idade média de início de tratamento muito acima da ideal. Isso resulta na impossibilidade de cumprimento do principal objetivo da triagem, que é o início precoce do tratamento para a prevenção de sequelas. Estudos recentes têm sugerido mudança do nível de corte do TSH para 6 mUI/l para reduzir os falso-negativos. Medidas devem ser adotadas para que os índices ideais do PNTN sejam atingidos.

Congenital disorders of the thyroid: hypo/hyper

This article summarizes the ontogenesis and genetics of the thyroid with regards to its possible congenital dysfunction and briefly refers to the roles of the mother-placenta-fetal unit, iodine effect, and organic and functional changes of the negative feedback mechanism, as well as maturity and illness, in some forms of congenital hypo- and hyperthyroidism. This article also describes the published literature and the authors' data on the clinical aspects of congenital hypothyroidism, on the alternating hypo- and hyperthyroidism in the neonatal period, and on neonatal hyperthyroidism.

Triagem neonatal: o conhecimento materno em uma maternidade no interior do Paraná, Brasil

Estudo transversal, quantitativo, realizado no Alojamento Conjunto de um hospital de médio porte, no interior do Paraná do qual fizeram parte 40 puérperas maiores de 18 anos. Teve como objetivo analisar o conhecimento desta população sobre a finalidade e importância da realização do "teste do pezinho" e caracterizá-la sócio-demograficamente. Os dados foram coletados em maio e junho de 2010, através de um questionário semi-estruturado elaborado e aplicado pelos próprios pesquisadores. A finalidade da triagem neonatal era conhecida por 65% (n=26) das participantes, observando-se que a maioria conhecia a finalidade e sabia sobre a importância da realização do "teste do pezinho", fato este que denota a importância das orientações que devem ser dispensadas a estas mães sobre o referido assunto, mesmo antes do nascimento do bebê, com enfoque ainda no pré-natal, destacando-se a importância do papel do enfermeiro neste contexto.

Primary blood TSH/back up TSH measurements: an improved approach for neonatal thyroid screening

OBJECTIVE

Neonatal hypothyroidism is one of the most common endocrine disorders related to mental impairment and growth retardation in newborns. In many countries, the neonatal thyroid screening programs are performed for rapid diagnosis and treatment of hypothyroidism. The major aim of this investigation was to improve the thyroid screening program using primary blood TSH/back up TSH measurements as some patients are missed due to technical and human errors.

METHODS

A total of 9,118 neonates were evaluated on the protocol. On top of that, the quality control procedures were applied to improve the sampling technique and the laboratory results.

RESULTS

Three missed neonates by current programs using the cutoff point more than 20  mU/l for blood TSH were found by our approach.

CONCLUSION

Results showed that the programs based on the primary blood TSH/back up TSH measurements improve the thyroid screening results.

Clinical monitoring guidelines for congenital hypothyroidism: laboratory outcome data in the first year of life

OBJECTIVE

To examine whether current recommendations for thyroid status monitoring in children with congenital hypothyroidism (CH) (monthly in the first 6 months and every 3-4 months subsequently) are adequate, or whether monthly monitoring is necessary throughout the first year.

STUDY DESIGN

We reviewed charts of 70 children with CH for initial thyroid-stimulating hormone (TSH), frequency of follow-up, dose changes, and thyroxine (T(4)) and TSH levels in the first year. Need for monthly monitoring was determined on the basis of guidelines to maintain T(4)/free T(4) in the upper half of the normal range and rapidly normalize TSH.

RESULTS

Monthly monitoring was justified in 75% in the first 6 months and 36% in the next 6 months. Children requiring monthly monitoring in the second 6 months had higher baseline TSH (P = .02) and lower T(4) (P = .01) than those not requiring monthly monitoring. Thyroid dysgenesis, starting levothyroxine dose, sex, and ethnicity did not predict requirement for monthly monitoring. Thirty percent of children in the first and second 6 months had ≥1 high TSH level, with a T(4)/free T(4) not in the upper half of the normal range.

CONCLUSION

More than a third of children with CH require monthly monitoring between 6 to 12 months on the basis of study criteria. Current monitoring guidelines may need to be reexamined.

Perinatal iron and copper deficiencies alter neonatal rat circulating and brain thyroid hormone concentrations

Copper (Cu), iron (Fe), and iodine/thyroid hormone (TH) deficiencies lead to similar defects in late brain development, suggesting that these micronutrient deficiencies share a common mechanism contributing to the observed derangements. Previous studies in rodents (postweanling and adult) and humans (adolescent and adult) indicate that Cu and Fe deficiencies affect the hypothalamic-pituitary-thyroid axis, leading to altered TH status. Importantly, however, relationships between Fe and Cu deficiencies and thyroidal status have not been assessed in the most vulnerable population, the developing fetus/neonate. We hypothesized that Cu and Fe deficiencies reduce circulating and brain TH levels during development, contributing to the defects in brain development associated with these deficiencies. To test this hypothesis, pregnant rat dams were rendered Cu deficient (CuD), FeD, or TH deficient from early gestation through weaning. Serum thyroxine (T(4)) and triiodothyronine (T(3)), and brain T(3) levels, were subsequently measured in postnatal d 12 (P12) pups. Cu deficiency reduced serum total T(3) by 48%, serum total T(4) by 21%, and whole-brain T(3) by 10% at P12. Fe deficiency reduced serum total T(3) by 43%, serum total T(4) by 67%, and whole-brain T(3) by 25% at P12. Brain mRNA analysis revealed that expression of several TH-responsive genes were altered in CuD or FeD neonates, suggesting that reduced TH concentrations were sensed by the FeD and CuD neonatal brain. These results indicate that at least some of the brain defects associated with neonatal Fe and Cu deficiencies are mediated through reductions in circulating and brain TH levels.

Congenital hypothyroidism

Congenital hypothyroidism (CH) occurs in approximately 1:2,000 to 1:4,000 newborns. The clinical manifestations are often subtle or not present at birth. This likely is due to trans-placental passage of some maternal thyroid hormone, while many infants have some thyroid production of their own. Common symptoms include decreased activity and increased sleep, feeding difficulty, constipation, and prolonged jaundice. On examination, common signs include myxedematous facies, large fontanels, macroglossia, a distended abdomen with umbilical hernia, and hypotonia. CH is classified into permanent and transient forms, which in turn can be divided into primary, secondary, or peripheral etiologies. Thyroid dysgenesis accounts for 85% of permanent, primary CH, while inborn errors of thyroid hormone biosynthesis (dyshormonogeneses) account for 10-15% of cases. Secondary or central CH may occur with isolated TSH deficiency, but more commonly it is associated with congenital hypopitiutarism. Transient CH most commonly occurs in preterm infants born in areas of endemic iodine deficiency. In countries with newborn screening programs in place, infants with CH are diagnosed after detection by screening tests. The diagnosis should be confirmed by finding an elevated serum TSH and low T4 or free T4 level. Other diagnostic tests, such as thyroid radionuclide uptake and scan, thyroid sonography, or serum thyroglobulin determination may help pinpoint the underlying etiology, although treatment may be started without these tests. Levothyroxine is the treatment of choice; the recommended starting dose is 10 to 15 mcg/kg/day. The immediate goals of treatment are to rapidly raise the serum T4 above 130 nmol/L (10 ug/dL) and normalize serum TSH levels. Frequent laboratory monitoring in infancy is essential to ensure optimal neurocognitive outcome. Serum TSH and free T4 should be measured every 1-2 months in the first 6 months of life and every 3-4 months thereafter. In general, the prognosis of infants detected by screening and started on treatment early is excellent, with IQs similar to sibling or classmate controls. Studies show that a lower neurocognitive outcome may occur in those infants started at a later age (> 30 days of age), on lower l-thyroxine doses than currently recommended, and in those infants with more severe hypothyroidism.

Neonatal screening for congenital hypothyroidism: a retrospective hospital based study from Bahrain

BACKGROUND

Neonatal screening programs for congenital hypothyroidism (CH) are now widespread in developed countries.

AIM

Cord blood thyroid-stimulating hormone (TSH) was evaluated for the incidence of CH in Bahrain Defense Force hospital.

METHODS

Those neonates with cord blood TSH values >25 mU/l were recalled. Permanent CH was reported when the levels of TSH and free T4 (fT4) venous blood samples were > or =15 mUl and <12 pmol/l, respectively, with abnormal thyroid scan.

RESULTS

Of 714 recalled newborns, 23 (10 males and 13 females) were diagnosed with transient TSH elevation with an estimated incidence of 1:774 births and 6 (3 males and 3 females) were diagnosed with permanent CH with an overall estimated incidence of 1:2,967 births.

CONCLUSIONS

High incidence rates for CH reported in this hospital-based study suggest the need for a national screening program for this congenital endocrine disorder in the Kingdom of Bahrain.

Update: newborn screening for endocrinopathies

Congenital hypothyroidism and congenital adrenal hyperplasia are included in many newborn screening (NBS) panels worldwide and in all state-sponsored programs in the United States. Both conditions meet the fundamental prerequisites for NBS: high incidence in the population; biomarkers in the dried blood specimen that are easily detected; and, effective therapies to lessen, if not prevent, the sequelae of late or no treatment. In this review, the history of NBS is discussed for these 2 conditions. The technologies and protocols used in their detection, and related subjects such as genetics, and treatment and outcomes, are also discussed.

Audit of initial management of congenital hypothyroidism in the United Kingdom--comparison of UK practice with European and UK guidelines

BACKGROUND

Prompt and adequate management of newly diagnosed congenital hypothyroidism (CH) has been shown to optimise intellectual outcome.

METHODS

A questionnaire survey of the British Society for Paediatric Endocrinology and Diabetes (BSPED) membership was undertaken, examining current clinical practice in neonatal CH. Results were compared with published management guidelines from Europe and the UK.

RESULTS

The response rate was 86%. The majority were largely compliant with both guidelines. 43% review newly referred infants on the day of notification. However, 26% treat severe CH with < 10 microg/kg/day thyroxine and nearly 20% do not follow up until at least 14 days after initiating treatment, in contrast to both guidelines. Despite a new liquid T4 preparation being licensed, respondents preferred tablet T4.

CONCLUSION

Rapidity of assessment and adequate follow up of suspected CH is critical to outcome. Existing European and UK guidelines should be reviewed and expanded to incorporate new evidence, together with increased advice on preparation and administration of T4.

Congenital disorders of the thyroid: hypo/hyper

This article summarizes the ontogenesis and genetics of the thyroid with regards to its possible congenital dysfunction and briefly refers to the roles of the mother-placenta-fetal unit, iodine effect, and organic and functional changes of the negative feedback mechanism, as well as maturity and illness, in some forms of congenital hypo- and hyperthyroidism. This article also describes the published literature and the authors' data on the clinical aspects of congenital hypothyroidism, on the alternating hypo- and hyperthyroidism in the neonatal period, and on neonatal hyperthyroidism.

Thyroid-disrupting chemicals: interpreting upstream biomarkers of adverse outcomes

BACKGROUND

There is increasing evidence in humans and in experimental animals for a relationship between exposure to specific environmental chemicals and perturbations in levels of critically important thyroid hormones (THs). Identification and proper interpretation of these relationships are required for accurate assessment of risk to public health.

OBJECTIVES

We review the role of TH in nervous system development and specific outcomes in adults, the impact of xenobiotics on thyroid signaling, the relationship between adverse outcomes of thyroid disruption and upstream causal biomarkers, and the societal implications of perturbations in thyroid signaling by xenobiotic chemicals.

DATA SOURCES

We drew on an extensive body of epidemiologic, toxicologic, and mechanistic studies.

DATA SYNTHESIS

THs are critical for normal nervous system development, and decreased maternal TH levels are associated with adverse neuropsychological development in children. In adult humans, increased thyroid-stimulating hormone is associated with increased blood pressure and poorer blood lipid profiles, both risk factors for cardiovascular disease and death. These effects of thyroid suppression are observed even within the "normal" range for the population. Environmental chemicals may affect thyroid homeostasis by a number of mechanisms, and multiple chemicals have been identified that interfere with thyroid function by each of the identified mechanisms.

CONCLUSIONS

Individuals are potentially vulnerable to adverse effects as a consequence of exposure to thyroid-disrupting chemicals. Any degree of thyroid disruption that affects TH levels on a population basis should be considered a biomarker of adverse outcomes, which may have important societal outcomes.