Useful parameters to predict the eventual mental outcome of hypothyroid children

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.

Guidelines for Newborn Screening of Congenital Hypothyroidism (2021 Revision)

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

Sonography of the distal femoral epiphysis in the etiological diagnosis of congenital hypothyroidism

The etiology of congenital hypothyroidism (CH) is often difficult to identify, owing mainly to limitations in currently available diagnostic tests. Characteristics of the distal femoral epiphyseal (DFE) ossification center may provide important information and help identify some causes of CH. We analyzed the contribution of DFE ultrasonography in the investigation of 11 young infants with positive screening for CH. DFE ultrasonography emerged as a simple test that helped indicate the period of onset of CH and, when associated with clinical history, hormone levels, and thyroid ultrasonography, contributed to suggest the etiology of CH.

Bone Maturation as a Predictive Factor of Catch-Up Growth During the First Year of Life in Born Small for Gestational Age Infants: A Prospective Study

Background: About 85-90% of children born small for gestational age (SGA) experience a catch-up growth that occurs mostly during the first year of life and results in a full stature recovery by the age of 2. Objective: To investigate the relation between bone maturation (BM) and catch-up growth during the first year of life in SGA infants. Method: Newborns whose weight and/or length was <-2 SD for gestational age were classified as SGA (group A). The study included a group of 32 SGA, 21 of which are full term [37-41 gestation weeks (GW), subgroup A1] and 11 preterm (30-36 GW, subgroup A2). Control group (B) consisted of 19 full-term and adequate-for-gestational-age (AGA) newborns. All the participants were born in the same hospital and period (January-December 2017). Chromosomal disorders, congenital defects, and maternal chronic diseases were criteria of exclusion. The study population underwent longitudinal evaluation of growth parameters and BM at 0, 3, 6, and 12 months. Assessment of BM was performed by an ultrasonographic (US) study of Béclard's nucleus (NB) (<3 mm at birth, meaning intrauterine delay of BM). Results: Significantly higher height velocity (HV) was observed in subgroup A2 vs. A1 (32.4 ± 8.0 vs. 25.6 ± 2.9 cm, p = 0.01); nevertheless, more subjects in subgroup A2 had height <-2 SD at year 1 than had subgroup A1 (27.3 vs. 0%, p = 0.01). Intrauterine delay of BM was more common in group A vs. B (59.4 vs. 21.2%, p = 0.0078) and in subgroup A2 vs. A1 (90.9 vs. 42.9%, p = 0.0086). In group A, HV over the first year of life negatively correlates with NB diameter assessed at birth (r = -0.6, p < 0.001) but positively correlates with NB growth (r = 0.52, p < 0.01). Moreover, SGA babies with intrauterine delay of BM showed higher HV and better height gain at 12 months' evaluation than did SGA with adequate BM (29.75 ± 3.1 vs. 23.8 ± 2.7 cm, p = 0.003). Conclusion: Neonatal BM should be regarded as a predictive factor of SGA height gain during the first year of life. US evaluation of NB is a useful noninvasive technique to identify intrauterine delay of BM, which positively correlates with early postnatal catch-up growth of SGA infants.

Iodine consumption and cognitive performance: Confirmation of adequate consumption

Iodine, a dynamic nutrient present in thyroid hormones, is responsible for regulating thyroid function, supporting a healthy metabolism, and aiding growth and development. Iodine is also essential for brain development during specific time windows influencing neurogenesis, neuronal and glial cell differentiation, myelination, neuronal migration, and synaptogenesis. About 1.5 billion people in 130 countries live in areas at risk of iron deficiencies (IDs). Reduced mental ability due to IDs occurs in almost 300 million people. Ensuring the consumption of minimum recommended daily allowances of iodine remains challenging. The effects of ID disorders range from high mortality of fetuses and children to inhibited mental development (cretinism). Poor socioeconomic development and impaired school performance are also notable. Currently, ID disorders are the single greatest contributor to preventable brain damage in fetuses and infants and arrested psychomotor development in children. Iodized salt may help fulfill iodine requirements. Increases in food salt iodization programs can help overcome ID disorders. Dietary plans can be well adjusted to incorporate iodinated foods. Maternal iodine supplementation for offspring requires adequate attention. Fruits, vegetables, bread, eggs, legumes (beans and peas), nuts, seeds, seafood, lean meats and poultry, and soy products provide small quantities of iodine. Nutrient-dense foods containing essential vitamins and minerals such as iodine may confer positive effects. To some extent, fortified foods and daily dietary supplements can be provided for different nutrients including iodine; otherwise, iodine may be consumed in less than the recommended amounts. This review focuses on aspects of adequate iodine consumption to avoid cognitive impairments.

A Rat Neurodevelopmental Evaluation of Offspring, Including Evaluation of Adult and Neonatal Thyroid, from Mothers Treated with Ammonium Perchlorate in Drinking Water

The purpose of this study was to evaluate the potential neurodevelopmental toxicity of perchlorate exposure during gestation and the first 10 days of lactation. Mated Sprague-Dawley rats (25/exposure group) were given continual access to 0, 0.1, 1.0, 3.0, or 10.0 mg/kg-day ammonium perchlorate (AP) in drinking water, starting gestation day 0 (mating) through lactation day 10 (DL 10). One pup/sex/litter/exposure group was assigned to (1) juvenile brain weights, morphometry, and neuropathology; (2) passive avoidance and watermaze testing; (3) motor activity and auditory startle habituation; and (4) adult regional brain weights, morphometry, and neuropathology. AP had no effect on body weights, feed consumption, clinical observations, or sexual maturation of pups at exposures as high as 10.0 mg/kg-day. There were no behavioral effects in the offspring exposed as high as 10.0 mg/kg-day as evaluated by passive avoidance, swimming watermaze, motor activity, and auditory startle. Increases in hypertrophy and hyperplasia of the thyroid follicular epithelium and a decrease in the thyroid follicle size were observed in culled male pups in the 10.0 mg/kg-day group on DL 5. The exposure level for effects on triiodothyroxine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) levels for pups were 0.1, 1.0, and 3.0 mg/kg-day, respectively. There was an apparent increase in the thickness of the corpus callosum of the 10 mg/kg-day group pups on DL 12. The no-observed-adverse-effect level (NOAEL) for maternal toxicity was greater than 10.0 mg/kg-day. Based on the thyroid morphometric and histopathologic findings, the NOAEL for pup toxicity was 0.1 mg/kg-day.

Guidelines for Mass Screening of Congenital Hypothyroidism (2014 revision)

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

Treatment of congenital thyroid dysfunction: Achievements and challenges

The active thyroid hormone tri-iodothyronine (T3) is essential for a normal development of children. Especially within the first years of life, thyroid hormone is pivotal in enabling maturation of complex brain function and somatic growth. The most compelling example for a life without thyroid hormone are those historical cases of children who came to birth without a thyroid gland - as shown in autopsy-studies- and who suffered from untreated hypothyroidism, at that time initially called "sporadic congenital hypothyroidism" (CH). In the last decades huge achievements resulted in a normal development of these children based on newborn screening programs that enable an early onset of a high dose LT4-treatment. Further progress will be necessary to further tailor an individualized thyroid hormone substitution approach and to identify those more complex patients with congenital hypothyroidism and associated defects, who will not benefit from an even optimized LT4 therapy. Besides the primary production of thyroid hormone a variety of further mechanisms are necessary to mediate the function of T3 on normal development that are located downstream of thyroid hormone production. Abnormalities of these mechanisms include the MCT8-transport defect, deiodinase-insufficiency and thyroid hormone receptor alpha-and beta defects. These thyroid hormone resistant diseases can not be treated with classical LT4 substitution alone. The development of new treatment options for those rare cases of thyroid hormone resistance is one of the most challenging tasks in the field of congenital thyroid diseases today.

European Society for Paediatric Endocrinology consensus guidelines on screening, diagnosis, and management of congenital hypothyroidism

OBJECTIVE

The aim was to formulate practice guidelines for the diagnosis and management of congenital hypothyroidism (CH).

EVIDENCE

A systematic literature search was conducted to identify key articles relating to the screening, diagnosis, and management of CH. The evidence-based guidelines were developed with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system, describing both the strength of recommendations and the quality of evidence. In the absence of sufficient evidence, conclusions were based on expert opinion.

CONSENSUS PROCESS

Thirty-two participants drawn from the European Society for Paediatric Endocrinology and five other major scientific societies in the field of pediatric endocrinology were allocated to working groups with assigned topics and specific questions. Each group searched the literature, evaluated the evidence, and developed a draft document. These papers were debated and finalized by each group before presentation to the full assembly for further discussion and agreement.

RECOMMENDATIONS

The recommendations include: worldwide neonatal screening, approaches to assess the cause (including genotyping) and the severity of the disorder, the immediate initiation of appropriate L-T4 supplementation and frequent monitoring to ensure dose adjustments to keep thyroid hormone levels in the target ranges, a trial of treatment in patients suspected of transient CH, regular assessments of developmental and neurosensory functions, consulting health professionals as appropriate, and education about CH. The harmonization of diagnosis, management, and routine health surveillance would not only optimize patient outcomes, but should also facilitate epidemiological studies of the disorder. Individuals with CH require monitoring throughout their lives, particularly during early childhood and pregnancy.

European Society for Paediatric Endocrinology consensus guidelines on screening, diagnosis, and management of congenital hypothyroidism

OBJECTIVE

The aim was to formulate practice guidelines for the diagnosis and management of congenital hypothyroidism (CH).

EVIDENCE

A systematic literature search was conducted to identify key articles relating to the screening, diagnosis, and management of CH. The evidence-based guidelines were developed with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system, describing both the strength of recommendations and the quality of evidence. In the absence of sufficient evidence, conclusions were based on expert opinion.

CONSENSUS PROCESS

Thirty-two participants drawn from the European Society for Paediatric Endocrinology and five other major scientific societies in the field of pediatric endocrinology were allocated to working groups with assigned topics and specific questions. Each group searched the literature, evaluated the evidence, and developed a draft document. These papers were debated and finalized by each group before presentation to the full assembly for further discussion and agreement.

RECOMMENDATIONS

The recommendations include: worldwide neonatal screening, approaches to assess the cause (including genotyping) and the severity of the disorder, the immediate initiation of appropriate L-T4 supplementation and frequent monitoring to ensure dose adjustments to keep thyroid hormone levels in the target ranges, a trial of treatment in patients suspected of transient CH, regular assessments of developmental and neurosensory functions, consulting health professionals as appropriate, and education about CH. The harmonization of diagnosis, management, and routine health surveillance would not only optimize patient outcomes, but should also facilitate epidemiological studies of the disorder. Individuals with CH require monitoring throughout their lives, particularly during early childhood and pregnancy.

Children with congenital hypothyroidism: long-term intellectual outcome after early high-dose treatment

We aim to determine long-term intellectual outcome of adolescents with early high-dose treated congenital hypothyroidism (CH). Sixty-three prospectively followed children with CH were assessed at age of 14 y with the Wechsler Intelligence Scale for Children-Revised and compared with 175 healthy controls. Median age at onset of treatment was 9 d (range 5-18 d) and median starting dose of levothyroxine (L-T4) was 14.7 microg/kg/d (range 9.9-23.6 microg/kg/d). Full-scale intelligence quotient (IQ) was significantly lower than in controls after adjustment for socioeconomic status (SES) and gender (101.7 versus 111.4; p < 0.0001). Children with athyreosis had a lower performance IQ than those with dysgenesis (adjusted difference 7.6 IQ scores, p < 0.05). Lower initial thyroxine (T4) levels correlated with poorer IQ (r = 0.27, p = 0.04). Lower SES was associated with poorer IQ, in particular in children with CH (interaction, p = 0.03). Treatment during childhood was not related to IQ at age 14 y. Adolescents with CH manifest IQ deficits when compared with their peers despite early high-dose treatment and optimal substitution therapy throughout childhood. Those adolescents with athyreosis and lower SES are at particular risk for adverse outcome. Therefore, early detection of intellectual deficits is mandatory in children with CH.

Programa de triagem neonatal para hipotireoidismo congênito no nordeste do Brasil: critérios diagnósticos e resultados

Avaliamos as concentrações do TSH em papel-filtro colhido no calcanhar (TSHneo) de 48.039 crianças triadas do programa de triagem neonatal (PTN) para o hipotireoidismo congênito (HC) de Sergipe, as concentrações de TSH, T4 total e T4 livre colhidas em sangue periférico nas crianças convocadas suspeitas de HC, a idade nas diversas fases do programa, a cobertura e a freqüência do PTN de janeiro de 2005 a agosto de 2006, comparando-as com dados da literatura. Utilizamos para análise os seguintes parâmetros: média, mediana, coeficiente de variação e distribuição de freqüência. A idade da criança por ocasião da coleta em papel filtro no calcanhar foi 10 ± 9 dias (média ± desvio-padrão) e a idade na reali-zação do ensaio do TSHneo foi de 31 ± 13 dias. Em 2005, a cobertura do PTN, para o interior e para a capital de Sergipe, foi de 77% e 73%, respectivamente. Verificamos que em 99,484% das crianças triadas as concentrações do TSH coletado em papel-filtro encontravam-se entre 0,01 e 5,20 µU/mL. As concentrações do TSH decrescem com o aumento da idade até estabilizar entre 11 e 15 dias de vida. Foram convocadas 248 crianças a partir do TSH coletado em papel-filtro (1/194). Na convocação, as concentrações do TSH, T4 e T4 livre coletado por punção venosa estavam normais em 119 crianças (1/404). A freqüência de HC suspeito foi de 1/485 (99 casos), de HC foi de 1/6.005 (8 casos) e de hipotiroxinemia foi de 1/16.013 (3 casos). A terapia para o HC foi iniciada com 51 ± 12 dias.

How should we be treating children with congenital hypothyroidism?

Early detection by newborn screening and appropriate L-thyroxine treatment leads to normal or near-normal neurocognitive outcome in infants with congenital hypothyroidism. Many newborns with congenital hypothyroidism have some residual thyroid hormone production, and even in those with athyreosis, transplacental passage of maternal thyroid hormone offers some protection for a time. Given the serum T4 half-life of 6 days, the neonatal T4 level will fall and disappear over the first 2-3 weeks of life. Thus, there is a crucial 'window of opportunity' to correct the hypothyroidism and minimize the time the brain is exposed to hypothyroxinemia. While there are few truly prospective, randomized clinical trials investigating treatment parameters, studies measuring IQ outcome support a starting L-thyroxine dose of 10-15 microg/kg/day. Further, studies show that the most severely hypothyroid infants are at risk for a 5-20 point decrease in IQ. Such infants may benefit from a starting dose of 12-17 microg/kg/d, which has been shown to normalize T4 in 3 days and TSH in 2 weeks. Target serum T4 or free T4 levels appear to be higher in the first two weeks of treatment. Infants require more frequent laboratory monitoring, every 1-2 months in the first 6 months and every 3-4 months until age 3 years, as the developing brain has a critical dependence on thyroid hormone in the first 2-3 years of life.

Development of a health-protective drinking water level for perchlorate

We evaluated animal and human toxicity data for perchlorate and identified reduction of thyroidal iodide uptake as the critical end point in the development of a health-protective drinking water level [also known as the public health goal (PHG)] for the chemical. This work was performed under the drinking water program of the Office of Environmental Health Hazard Assessment of the California Environmental Protection Agency. For dose-response characterization, we applied benchmark-dose modeling to human data and determined a point of departure (the 95% lower confidence limit for 5% inhibition of iodide uptake) of 0.0037 mg/kg/day. A PHG of 6 ppb was calculated by using an uncertainty factor of 10, a relative source contribution of 60%, and exposure assumptions specific to pregnant women. The California Department of Health Services will use the PHG, together with other considerations such as economic impact and engineering feasibility, to develop a California maximum contaminant level for perchlorate. We consider the PHG to be adequately protective of sensitive subpopulations, including pregnant women, their fetuses, infants, and people with hypothyroidism.

Congenital hypothyroidism: From paracelsus to molecular diagnosis

Endemic cretinism was noted in alpine Europe as early as the 13th century. However, it was only in 1848 that a commission, sponsored by the King of Sardinia, first formally demonstrated its link to goiter. An important landmark was the publication of a report in 1871 describing several cases of nongoitrous hypothyroidism that were clearly distinguished from the endemic form of the disease, for which the author suggested the designation of "sporadic cretinism." Classification of the hypothyroid status was for a long time solely based on clinical observation. In the second half of the 20th century, the use of radionuclides (iodine radioisotope and technetium pertechnetate) allowed a more precise diagnosis and taxonomy into thyroid dysgenesis and dyshormonogenesis. This brief review summarizes the progress that has been achieved during the last 40 years in diagnosing the multiple variants of congenital hypothyroidism (CH). It becomes evident that while accurate diagnosis for CH is readily available, its exact etiology requires a precise molecular investigation as different genes are implicated in the differentiation, migration and growth of the thyroid gland.

Evolução do programa de triagem neonatal para o hipotireoidismo congênito e fenilcetonúria no Estado de Sergipe de 1995 a 2003

Avaliamos o tempo gasto nas diferentes etapas do Programa de Triagem para o Hipotireoidismo Congênito (HC) e Fenilcetonúria (PKU), sua cobertura e a freqüência em Sergipe, de 1998 a 2003, e comparamos com 1995. A idade da criança na coleta foi 12 ± 11 dias (Média ± Desvio Padrão) em 2003, inferior aos 30 ± 19 dias no 2º semestre de 1995. No 2º semestre/2003, o resultado foi analisado pelo médico com 28 ± 15 dias para o HC e 25 ± 15 dias para o PKU, menor que o tempo utilizado pelo médico no 2º semestre de 1995, 80 ± 40 dias. O tempo, no 2º semestre de 2003, entre o recebimento da amostra da coleta no laboratório e a realização do ensaio foi de 6 ± 4 dias para o TSH e de 3 ± 2 dias para a fenilalanina. A cobertura, em 2003, para o Interior foi de 67% e 85% para a Capital contra 5% e 42% no 2º semestre de 1995, respectivamente. A incidência de 1998 a 2003, no Serviço Público de Saúde de Sergipe para o HC, foi de 1/4850 e para o PKU, de 1/23036. De 1998 a 2003, a terapia foi iniciada com 49 ± 17 e 51 ± 12 dias para o HC e PKU, respectivamente. A redução do tempo nas etapas do programa e o aumento da cobertura indicam uma evolução favorável do referido programa.

Congenital hypothyroidism: developmental outcome in relation to levothyroxine treatment variables

Neonatal screening programs for congenital hypothyroidism (CH) were initiated in the 1970s to ensure early treatment in order to prevent mental retardation. With screening, developmental prognosis is considerably improved, but follow-up studies still report developmental delay compared to controls. To explain the delay, most studies have focused on effects of CH severity, supposedly caused by prenatal hypothyroidism. Nonoptimal treatment could also be an explanatory factor. Treatment guidelines have changed; now, a higher levothyroxine starting dose is recommended. In this review, we first summarize outcome studies in CH versus controls and in mild versus severe CH. Second, we report results on the association between levothyroxine treatment variables and developmental outcome. Six research groups have reported results on the association between levothyroxine starting dose and intelligence, and eight groups on the association between circulating thyroid hormones and intelligence. Most studies found a positive association between a high level of treatment, primarily treatment during the first year and later intelligence. However, negative associations between high-dose treatment and outcome have been reported, and the question of optimal treatment in relation to developmental outcome has not been answered. Effects of high levothyroxine dosage should be documented in samples that have been treated according to recent recommendations.

Congenital hypothyroidism: a review of current diagnostic and treatment practices in relation to neuropsychologic outcome

Because thyroid hormone is essential for normal brain development, children born with congenital hypothyroidism who lack thyroid hormone during a circumscribed period of early development are at risk of brain damage and mental retardation. Since the advent of newborn screening programs in the 1980s, the diagnosis and treatment of this condition are now provided in the first 2-3 weeks of birth in most regions. While this is usually sufficient to prevent mental retardation, the children so identified attain mildly reduced IQs from expectation, and may still experience subtle and specific neurocognitive deficits. Their particular deficits are related to the brief period of thyroid hormone insufficiency they undergo, especially factors reflecting the severity of hypothyroidism at the time of diagnosis, the duration of hypothyroidism in infancy, and thyroid hormones at time of testing. In this article, we review the specific kinds of deficits demonstrated by children with congenital hypothyroidism who were diagnosed by screening and treated early, as well as the factors associated with their disease and its management that contribute to these deficits. The disease-related factors that will be reviewed will include the etiology of hypothyroidism and severity of disease at the time of diagnosis, while the treatment-related factors will include age at onset of therapy, starting and subsequent dose levels, compliance, and treatment-adequacy issues. Also examined will be the effects of hormone levels at the time of testing. In addition, the role of moderating variables such as social, genetic, and environmental influences, as well as the child's gender, will be discussed. Furthermore, several new issues including the quality of subsequent management, ultimate outcome, and pregnancy will be additionally reviewed. In conclusion, while outcome in congenital hypothyroidism is substantially improved by screening, affected children do still experience mild neuropsychologic deficits. To reduce the impact of persisting deficits, further research is needed to determine the optimal starting dose for the different etiologies, guidelines for subsequent management, and alternative therapies. Moreover, now that the original samples are reaching adulthood and, in females, childbearing age, further research is also needed regarding treatment during pregnancy in women with congenital hypothyroidism, as is research to determine how this population ultimately fares in adulthood.

Auditory brainstem evoked potentials in early-treated congenital hypothyroidism

To evaluate the effect of early treatment of congenital hypothyroidism on central nervous system development, auditory brainstem evoked potentials were determined in 32 patients with hyperthyrotropinemia diagnosed during neonatal screening. The patients included 27 with congenital hypothyroidism and 5 with transient hypothyroidism. Abnormal auditory brainstem evoked potential tracings were found in 8 patients (congenital hypothyroidism in 7 and transient hypothyroidism in 1). Four of these patients had increased peripheral conduction time (wave I prolongation), and the other 4 had increased central conduction time (wave III or V prolongation). The patients with abnormal auditory brainstem evoked potentials did not show increased initial manifestations, yet 6 of them had lower initial thyroxine levels. Specific auditory brainstem evoked potential abnormalities were found in 25% of early-treated patients with congenital hypothyroidism. The possible causal relationship between deviant auditory brainstem evoked potential patterns and later neurodevelopment demands further clarification. This study suggests the usefulness of auditory brainstem evoked potential assessment to provide information about electrophysiologic deviation of the auditory pathway in patients with early-treated congenital hypothyroidism.

Effect of different starting doses of levothyroxine on growth and intellectual outcome at four years of age in congenital hypothyroidism

To evaluate the effect of different initial levothyroxine (LT4) replacement doses on growth and intellectual outcome in patients with congenital hypothyroidism (CH) detected by neonatal screening program, the longitudinal growth and intelligence quotient (IQ) were assessed and compared at 4 years of age in 83 patients with CH. The patients were divided into three groups according to the initial LT4 dose used: (1) group 1 (n = 42) received the previously recommended dose of 6.0-8.0 microg/kg per day; (2) group 2 (n = 21) received a dose of 8.1-10.0 microg/kg per day; (3) Group 3 (n = 20) a dose of 10.1-15.0 microg/kg per day. The IQ, evaluated by the Wechsler Preschool and Primary Scale of Intelligence test at 4 years of age, was significantly higher in group 3 (IQ 98 +/- 9) compared to group 1 (IQ 88 +/- 13; p < 0.05) but not compared to group 2 (IQ 94 +/- 13). However, the IQs were below the normal range (< 85) in six patients from group 2 (28%), but in none of the patients from group 3 (p = 0.03). Patients from group 3, with severe CH at diagnosis, had an IQ (97 +/- 9) at 4 years of age, which was not different from that of patients from the same group with moderate CH at diagnosis (IQ 99 +/- 9). Similar results were also observed in patients from group 2 however, mean IQ scores in these patients (93 +/- 12) were several points lower than those observed in patients from group 3 (95 +/- 15). After the first month of treatment, optimal serum levels of thyroxine (T4) and free thyroxine (FT4) were achieved in all groups, however, only patients from group 3 were able to normalize thyrotropin (TSH) (group 1, 16.0 +/- 12.0; group 2, 9.2 +/- 10.0; and group 3, 2.4 +/- 3.3 mU/L; p < 0.0001). Twelve patients from group 2 treated with an initial LT4 dose above 9 microg/kg per day were able to normalize TSH levels within the first 3 months of life and this resulted in a better IQ (97 +/- 16) compared to the remaining patients from the same group (IQ 90 +/- 9). In the whole group of 83 patients the IQ at 4 years of age was positively correlated to both initial LT4 dosage (r = 0.27, p < 0.02) and FT4 concentrations after the first month of treatment (r = 0.29, p < 0.02), and negatively correlated to TSH concentrations after the first month of treatment (r = -0.27, p < 0.02). No significant differences were observed in height, weight, head circumference, and bone age maturation among the three groups of patients. No clinical signs or symptoms of overtreatment were observed during follow-up in patients receiving the higher LT4 dosage. Our results indicate that high LT4 starting doses rapidly normalize serum TSH concentrations resulting in an improvement of the IQ at 4 years of age, even in patients with severe CH at diagnosis. Growth and bone age maturation are not affected by such a high dose.

The influence of etiology and treatment factors on intellectual outcome in congenital hypothyroidism

To determine the effects of hypothyroidism and hormonal patterns on outcome, we tested 65 7- to 12-year-old children with congenital hypothyroidism using standardized tests of intelligence, neuropsychological functioning, memory, and achievement. Results were analyzed by etiology, time to thyrotropin normalization, and hormone levels at testing. Children with athyreosis scored below other etiologies on visuospatial, attention, and arithmetic indices. Children whose thyroid-stimulating hormone levels normalized by 1 to 2 months of age scored higher than later normalizers on indices of visual memory, attention, and arithmetic. Normalization of thyroid-stimulating hormone by 3 months of age was associated with better memory and learning abilities than later normalization. Thyroid hormone levels at testing were correlated with indices of sensorimotor, spatial, and language abilities. Two children with persistently elevated thyrotropin levels were not adversely affected. Present findings signify the need to establish etiology, normalize thyrotropin early, and maintain hormone levels in the normal range throughout childhood in children with congenital hypothyroidism.

Avaliação do programa de triagem para o hipotireoidismo congênito no estado de Sergipe

Nesta pesquisa fizemos uma avaliação da oportunidade nas diversas etapas que compõem o mecanismo de detecção do Programa de Triagem para o Hipotireoidismo Congênito, sua cobertura e a freqüência de casos no serviço público de saúde em Sergipe. Levantamos a idade de todas as crianças (2994) submetidas à triagem para detecção neonatal do hipotireoidismo congênito e fenilcetonúria em suas diversas fases, no período de junho a dezembro de 1995. A idade da criança na coleta do exame, foi de 30±19 dias (média±DP). A idade, quando o resultado da triagem chegou ao centro de saúde, foi de 48±7 dias, quando entregue à família, de 66±18 dias e quando visto pelo pediatra da unidade, de 80±40 dias. Crianças com resultados alterados são referidas para serviços especializados sem nenhum pacto de prioridade. Com relação à cobertura, apenas 5% das crianças do interior do Estado e 42% da capital foram examinadas. A morosidade nas etapas do programa e a baixa cobertura de crianças submetidas ao teste de triagem comprovam a hipótese de que o referido programa de governo não está atingindo seus objetivos principais que são o tratamento oportuno e a cobertura a todas as crianças recém-nascidas, a fim de que sejam prevenidas suas seqüelas.

Neonatal hypothyroidism: treatment and outcome

Systematic neonatal screening for congenital hypothyroidism (CH), which was progressively implemented in industrialized countries over the past 15 to 25 years, has been extremely successful in eradicating severe mental deficiency resulting from CH. However, in the first generation of children diagnosed by screening, the concept that CH has a threshold effect on intelligence was confirmed. In spite of earlier diagnosis through screening, children with severe CH (i.e., those with a marked retardation of bone age and/or a low circulating thyroxine [T4] before treatment) still had clinically significant intellectual sequelae, amounting to a loss of 6 to 19 IQ points. Recent studies suggest that this developmental gap may be closed by treating more rapidly after birth (2 weeks instead of 4-5 weeks in the early years of the screening era) and by using a higher initial dose of levothyroxine (10-15 instead of 5-8 microg/kg per day). This regimen induces transient hyperthyroxinemia, but no clinical signs or symptoms of hyperthyroidism. Longer term follow-up of larger numbers of patients remains necessary to confirm the normalization of intellectual development and the absence of untowards effects of the treatment regimen in children with severe CH.

Urinary compound W in pregnant women is a potential marker for fetal thyroid function

OBJECTIVE

Previously we reported 3,3'-diiodothyronine sulfate-like material (compound W) in maternal serum, and studies suggest that compound W is derived from thyroid hormones of fetal origin. In this study we characterized gestational changes of urinary compound W concentrations to correlate with changes in serum concentrations.

STUDY DESIGN

Urinary samples were collected from 94 women at various gestational ages ranging from 3 to 40 weeks. Urinary compound W was first identified biochemically. The concentrations of compound W (adjusted for creatinine levels) were assessed by a 3,3'-diiodothyronine sulfate radioimmunoassay in ethanol extracts of urine samples.

RESULTS

Compound W increased to 88 +/- 1.4 pmol (of 3,3'-diiodothyronine sulfate equivalent)/mmol creatinine in urinary samples obtained from 26 women in the first trimester of pregnancy compared with 40 +/- 6.9 pmol/mmol creatinine in 10 nonpregnant women. Excretion of compound W increased further during the second and third trimesters: 171 +/- 17 (n = 18) and 434 +/- 26 (n = 50) respectively. In contrast, urinary 3,3',5-triiodothyronine sulfate concentrations measured by radioimmunoassay were similar during pregnancy to values in nonpregnant women.

CONCLUSIONS

Urinary compound W concentrations increase with the progression of normal pregnancy and correlate with the increase in serum levels. Random spot urine compound W concentrations, adjusted for creatinine levels, may be used in place of serum levels in conditions in which obtaining serum samples may be technically difficult, especially during population screening.

[Results of national evaluation tests (primary schools) of CE2 and 6th classes of 73 students with congenital hypothyroidism screened at birth]

Assessment of school performance provides an excellent index of adequacy of therapy of congenital hypothyroidism.

PATIENTS AND METHODS

Scholarly achievement of 73 children with congenital hypothyroidism screened and followed-up in our clinic was evaluated by comparison to national tests calculated from a wide random sample. The 73 children were divided into three groups: 31 patients belonging to the CE2 class (third primary school class) (group 1); 13 patients belonging to the 6th class (first secondary school class) having already passed CE2 tests (group 2); and 16 patients also belonging to the 6th class but not having passed CE2 tests (group 3).

RESULTS

The youngest patients showed better results in French than national means, with similar results in mathematics. The intermediate aged patients showed comparable scores to the national mean in both tests. The oldest patients showed significantly less achievement in mathematics, and somewhat (but not markedly) less achievement in French. Etiology of hypothyroidism did not seem to be a prognostic factor, with the athyreotic patients having better results in CE2 than ectopic ones. Age at onset of treatment and the duration of treatment before normalization of thyroid stimulating hormone (TSH) seemed to represent the main prognostic factors as does compliance to treatment, which depends on socioeconomic levels of families.

CONCLUSION

Encouraging results are now obtained in those patients who have been screened in the neonatal period and treated very early. Compliance to the treatment remains an important factor of prognosis.

Timing variability in children with early-treated congenital hypothyroidism

This study reports on central and peripheral determinants of timing variability in self-paced tapping by children with early-treated congenital hypothyroidism (CH). A theoretical model of the timing of repetitive movements developed by Wing and Kristofferson was applied to estimate the central timekeeper (clock) and peripheral implementation (motor delay) variances from the variability in the response intervals. Before it is diagnosed and treated, CH is known to affect proper development of the cerebellum. If this would affect the time-keeper function of the cerebellum, it should be reflected by an increased central clock variability rather than by an increased peripheral motor-delay variability in terms of the Wing and Kristofferson model. Results of 46 children with early-treated CH, differing in severity (21 severe, 25 mild), and 34 normal controls are reported. A refinement of the Wing and Kristofferson model is applied to estimate central clock and peripheral motor delay timing variability more precisely than has been done before. Results show that for children with early-treated CH the estimate of the motor delay variance is four times higher than for the controls, while the estimate of the clock variance does not differ between the groups. It is concluded that motor problems in early-treated CH are associated with peripheral rather than with central timing deficiencies.

Reported biomedical causes and associated medical conditions for mental retardation among 10-year-old children, metropolitan Atlanta, 1985 to 1987

This report describes biomedical causes of mental retardation (MR) among school-age children and associated medical conditions in children for whom no cause was reported. This study involved 715, 10-year-old children with MR (intelligence quotient [IQ] 70 or less) born between 1975 and 1977. We determined biomedical causes of MR using a hierarchical approach based on the timing of the event (i.e. prenatal, perinatal, or postneonatal). Among children with no identified biomedical cause the occurrence of associated medical conditions was examined. No reported biomedical cause could be found in 78% of children with MR (87% mild, IQ 50 to 70; 57% severe, IQ < 50). Prenatal causes were present in 12%, perinatal causes in 6%, and postneonatal causes in 4%. On the basis of these findings it was concluded that intensive use of public health prevention strategies can reduce the number of children who receive a diagnosis of MR.

Fetal thyroid function: diagnosis and management of fetal thyroid disorders

The fetal hypothalamic-pituitary-thyroid axis develops independently of the maternal axis, but it is dependent on the maternal-placental system for adequate supply of iodide substrate. This iodide is supplied by direct transfer of maternal plasma iodide and by placental deiodination of T4. In addition, although placental transport of iodothyronines is limited, significant maternal-fetal transfer of T4 occurs, accounting for approximately 30% of the average 10 ug/dL serum-T4 concentration in fetal-cord blood at term. Current information suggests that this maternal contribution to the fetal-T4 levels is important for normal fetal maturation, particularly of the central nervous system. Combined maternal-fetal hypothyroxinemia can lead to irreversible fetal central nervous system damage. The timing of this fetal T4 dependency is not clear. It may be important in the first half of gestation, before the fetal thyroid gland is capable of T4 production, as well as the latter half of gestation when thyroid hormone effects on multiple organ systems are developing. Management of fetal thyroid dysfunction requires normalization of maternal serum T4 concentrations, avoidance or careful monitoring of potentially goitrogenic drug effects in the fetus, and in some instances, direct or indirect fetal therapy. In most cases fetal hypothyroidism is sporadic and undetected, and prognosis for normal growth and development is excellent if the mother is euthyroid and the hypothyroid state is detected and adequately treated at birth. Fetal treatment by intraamniotic thyroxine injection has been provided in cases of inadvertent maternal radioiodine treatment of Graves' disease between 10 and 20 weeks gestation and for fetal goiter detected by ultrasound. Effective treatment of fetal hyperthyroidism in pregnant women with high titers of thyroid stimulating autoantibody is possible by judicious administration of antithyroid drugs to the mother. Management of the hyperthyroid state in the neonate also is essential.

Thyroid hormone and attention in school-age children with congenital hypothyroidism

The relationship between attention and thyroid hormone was examined using a retrospective database of 85 7-year-old children with congenital hypothyroidism who received psychological evaluations and thyroid function tests on the same day. Four unique subgroups with different levels of thyroxine and thyrotropin were compared on psychological tasks and measures of attention. Children with high levels of both hormones were found to be significantly more distractable on an index of cognitive attention but were reportedly less hyperactive. Level of thyroxine accounted for over 10% of the variance in attention.

Treatment variables as predictors of intellectual outcome in children with congenital hypothyroidism

The purpose of this study was to assess how much of the variance in intellectual outcome at 2 and 6 years of age could be attributed to treatment variables in children with congenital hypothyroidism, and which of the parameters used for monitoring treatment predicted later development. Forty-five children, early treated according to general recommendations, were studied. Linear multiple regression analysis was used, controlling for socio-economic status and the pretreatment serum thyroxine concentration. At 2 years of age, 19% of the variance in Mental Development Index (Bayley Scales of Infant Development) was attributed to treatment variables: combinations of serum thyroxine and serum TSH during the 1st year and bone age at mean age 1.5 years (mean z-scores). At 6 years of age, 35% of the variance in Verbal IQ (Wechsler Preschool and Primary Scale of Intelligence) was attributed to treatment variables: 13% to the mean serum thyroxine concentration during the 1st year, 12% to the initial L-thyroxine dose per kilogram body weight per day, and 10% to a combined measure for serum thyroxine and serum TSH during the 2nd year (mean z-score).

CONCLUSION

Both the initial L-thyroxine dosage and treatment variables during the 1st and the 2nd year (serum thyroxine, serum TSH and bone age) predicted later intellectual outcome in children with congenital hypothyroidism.

Neuropsychologic development in early treated congenital hypothyroidism: analysis of literature data

The aim of this study was to determine the neuropsychologic development in patients with congenital (primary) hypothyroidism (CH) detected by screening and treated from early age. Seven studies were evaluated, including 675 CH patients and 570 controls. Criteria for inclusion of the studies were: 1) age of patients and controls > or = 5 y; 2) control group well defined in the original article. A meta-analysis of the data on the intellectual development was performed. All analyzed studies show a trend toward lower intelligence quotient (IQ) and--as far as investigated--poorer motor skills in CH patients compared with controls. Pooling of data showed a significant deficit of the mean IQ of 6.3 (95% confidence interval: 4.7-7.8). The most important independent risk factor for the eventual outcome appears to be the severity of CH (defined by initial thyroxine at the moment of diagnosis and by skeletal maturation); treatment variables do not seem to have an important effect the cognitive development. We conclude that CH, despite early detection and treatment, results in an IQ deficit; the severity of CH seems to be the most important individual risk factor. Our second conclusion is that, although biomedical risk factors are well investigated, the individual weight of these factors is yet largely unknown. This may be due to the variability of definitions and test tools, especially for the investigation of motor skills, that have been used.

Outcome of lower L-thyroxine dose for treatment of congenital hypothyroidism

The appropriateness of the recommended L-thyroxine dose (10-15 micrograms/kg/day) for the treatment of congenital hypothyroidism has been questioned because of the risk of iatrogenic hyperthyroidism. We report the outcome of 23 newborns with congenital primary hypothyroidism treated with 25 micrograms L-thyroxine per day (5.3-9.2 micrograms/kg/day) and followed for an average of 59 months. Serum thyroxine (T4) values increased (X = 11.4 +/- 2.7 micrograms/dL) within 4 weeks posttherapy; eight infants had T4 levels > or = 13 micrograms/dL on only half the currently recommended dose. Thyroid-stimulating hormone (TSH) values remained elevated in 18 of 21 patients for 2-21 months despite a high-normal T4. Psychometric tests were performed in 19 of the 23 patients. The mean Full Scale IQ for the congenital hypothyroid group (n = 16) was 101.4 +/- 13.2 with comparable Verbal and Performance IQ scores. Patients with a bone age (BA) of < or = 32 weeks or T4 < 2 micrograms/dL at initial evaluation had significantly Lower Verbal IQ scores. A standardized parent-report assessment of behavioral and emotional functioning revealed subgroup scale scores that were indistinguishable from nonclinical norms. We conclude that (1) average range IQ scores and positive behavioral adaptation are observed in congenitally hypothyroid children treated with L-thyroxine doses lower than currently recommended; (2) the L-thyroxine dose should be individualized to prevent iatrogenic hyperthyroidism; (3) TSH normalization should not be a primary objective of treatment, and (4) a prospective study comparing the advantages and risks of different doses of L-thyroxine is needed.

Relation between biochemical severity and intelligence in early treated congenital hypothyroidism: a threshold effect

OBJECTIVES

To assess whether early treatment of congenital hypothyroidism fully prevents intellectual impairment.

DESIGN

A national register of children with congenital hypothyroidism who were compared with unaffected children from the same school classes and matched for age, sex, social class, and first language.

SETTING

First three years (1982-4) of a neonatal screening programme in England, Wales, and Northern Ireland.

SUBJECTS

361 children with congenital hypothyroidism given early treatment and 315 control children.

MAIN OUTCOME MEASURES

Intelligence quotient (IQ) measured at school entry at 5 years of age with the Wechsler preschool and primary scale of intelligence.

RESULTS

There was a discontinuous relation between IQ and plasma thyroxine concentration at diagnosis, with a threshold at 42.8 nmol/l (95% confidence interval 35.2 to 47.1 nmol/l). Hypothyroid children with thyroxine values below 42.8 nmol/l had a mean IQ 10.3 points (6.9 to 13.7 points) lower than those with higher values and than controls. None of the measures of quality of treatment (age at start of treatment (range 1-173 days), average thyroxine dose (12-76 micrograms in the first year), average thyroxine concentration during treatment (79-234 nmol/l in the first year), and thyroxine concentration less than 103 nmol/l at least once during the first year) influenced IQ at age 5.

CONCLUSIONS

Despite early treatment in congenital hypothyroidism the disease severity has a threshold effect on brain development, probably determined prenatally. The 55% of infants with more severe disease continue to show clinically significant intellectual impairment; infants with milder disease show no such impairment. The findings predict that 10% of early treated infants with severe hypothyroidism, compared with around 40% of those who presented with symptoms in the period before screening began, are likely to require special education.

Skeletal maturation during thyroxine treatment in children with congenital hypothyroidism

The aim of this investigation was to study if bone age development (assessed by the Greulich & Pyle atlas) was related to L-thyroxine treatment in 47 children with congenital hypothyroidism, treated early and according to general recommendations. In spite of frequent delay in skeletal maturation at diagnosis, the delay in mean bone age at a mean chronological age of 1.5 years was slight (0.5 months), and 30% of the variation in bone age SD score (SDS) at 1.5 years was accounted for by the dose of L-thyroxine and serum thyroxine during the first year. The children with a bone age within +/- 1 SDS had a prescribed mean dose of L-thyroxine per kg body weight from 3 to 12 months of age of 5.4 +/- 1.7 micrograms/kg/day, and their mean serum thyroxine concentration during the first year was 175 +/- 29 nmol/l. We conclude that bone age at 1.5 years of age was positively correlated with the dose of L-thyroxine and the serum thyroxine concentrations during the first year. This supports the general use of bone age assessments as a complement to other treatment variables in the follow-up of children with congenital hypothyroidism.

Motor and cognitive development in children with congenital hypothyroidism: a long-term evaluation of the effects of neonatal treatment

Although neonatal thyroid screening programs have been of value in preventing cerebral damage, it is still controversial whether patients with congenital hypothyroidism achieve normal motor and cognitive skills. We studied the motor and cognitive skills of 72 children with early-treated congenital hypothyroidism and 35 control subjects at the ages of 7 1/2 and 9 1/2 years. The relative influence of cause, blood thyroxine concentration at the time of screening, and age at the start of thyroxine replacement therapy on motor and cognitive development was investigated. Despite having received treatment at a mean age of 23 days, children with low neonatal thyroxine concentrations (< 50 nmol/L) at screening, particularly children with thyroid agenesis, had significant motor problems and borderline intelligence scores as late as 9 1/2 years of age. Balance and gross motor functions seemed to decline between 7 1/2 and 9 1/2 years of age, whereas language and memory functions seemed to be maintained. Significant correlations between the start of therapy and both motor scores and performance IQ scores at the age of 7 1/2 years in children with severe hypothyroidism show the importance of early treatment for these patients.

Effects of perinatal exposure to specific PCB congeners on thyroid hormone concentrations and thyroid histology in the rat

Time-mated Sprague-Dawley rats were exposed to PCB 28 (2,4,4'-trichlorobiphenyl), 8 or 32 mg/kg/day; PCB 118 (2,3',4,4',5-pentachlorobiphenyl), 4 or 16 mg/kg/day; or PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl), 16 or 64 mg/kg/day. At weaning, serum thyroxine (T4) was markedly depressed in pups, but not dams, exposed to PCB 118 or 153. Triiodothyronine (T3) was unchanged in pups and dams. In a histological evaluation of thyroids, the PCB 118 pups revealed changes suggestive of sustained TSH stimulation, including increased follicular cell vacuolization and height, increased nuclear vesiculation, and decreased colloid area. Decreases in body and brain weights and increases in liver weights were observed in some groups, with the high dose PCB 118 pups showing the greatest effect.

Intellectual development at age 12 years of children with congenital hypothyroidism diagnosed by neonatal screening

Twenty-seven patients with congenital hypothyroidism diagnosed by neonatal screening were examined at the age of 12 years. The 12 patients with severe hypothyroidism at diagnosis (thyroxine < 2 micrograms/dl (< 26 nmol/L), and area-of-the-knee epiphyses < 0.05 cm2 had a lower IQ than the 15 patients with less severe hypothyroidism (mean +/- SD, 89 +/- 17 vs 104 +/- 10; p < 0.007). Comparisons of patients and siblings confirm that this difference was due to the severity of hypothyroidism.

Congenital hypothyroidism

Because of the lack of signs and symptoms in the first weeks of life, the most important tool for the early diagnosis of congenital hypothyroidism is a newborn screening program.

Evaluation of L-thyroxine replacement therapy in children with congenital hypothyroidism

The outcome of L-thyroxine (L-T4) replacement therapy in children with congenital hypothyroidism (CH) remains to be completely evaluated. In this paper the overall pattern of response to L-T4 replacement therapy was studied in a group of 19 children with CH diagnosed by neonatal screening (10 with hypoplastic/aplastic thyroid disease, group H/A; 9 with gland ectopy, group E) who were followed-up for 60 +/- 27 months (mean +/- SD). With 1 exception serum T4 at diagnosis was greater than 2 micrograms/dl in children of group E and less than 2 micrograms/dl in those of group H/A. The initial dose of L-T4 (8-10 micrograms/kg BW/day) was modified in relation to age and weight in order to maintain serum TSH less than or equal to 5 microU/ml and FT3 in the normal range. A general inverse correlation between serum TSH and FT4 or FT3 concentrations was found, and the mean levels of serum FT4 and FT3 were significantly higher according to the following order of TSH results: low TSH (0-0.5 microU/ml) greater than normal (greater than 0.5-5 microU/ml) greater than elevated TSH (greater than 5 microU/ml). TSH levels less than or equal to 5 microU/ml were associated with FT4 values in the upper half of the normal range (54% of observations) or even higher (46%). Elevation of serum FT4 alone with FT3 values in the normal range did not result in clinical thyrotoxicosis, alteration of growth or premature craniosynostosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Intelligence, motor skills and behaviour at 5 years in early-treated congenital hypothyroidism

The cognitive functioning, motor skills and behaviour of 5-year-old children with early-treated congenital hypothyroidism was assessed. The study group was 57 children with congenital hypothyroidism (CH) diagnosed by neonatal screening in N.E. and N.W. Thames regions between 1978 and 1981 along with 51 non-affected controls matched for age, sex, social class and language background. Small differences in I.Q. and behaviour between the patients and the controls were not statistically significant. However, children with CH showed significant deficits in motor skills (M 79.9 SE 3.7) compared to the controls (M 99.8 SE 4.0) (P = 0.0003). Deficits were particularly marked for balance. In addition, children with more severe hypothyroidism at diagnosis (Plasma thyroxine less than 20 nmol/l) did significantly less well in respect to I.Q. and motor skills than those with less severe hypothyroidism (plasma thyroxine greater than 60 nmol/l). These findings provide further evidence for the importance of the severity of hypothyroidism in determining the outcome for intelligence and motor skills in children with early-treated congenital hypothyroidism. Deficits in motor skills, particularly in relation to balance, suggest that early impairment of the vestibular system may occur despite early treatment.

Intellectual development in children with congenital hypothyroidism in relation to recommended thyroxine treatment

The relationship between the treatment serum thyroxine level and intellectual development at 2 and 6 years was investigated in 46 Norwegian children with congenital hypothyroidism identified by neonatal screening. The level of serum thyroxine during the first 2 years was positively correlated with the Mental Development Index at 2 years of age (Bayley Scales of Infant Development) and the Verbal IQ at 6 years of age (Wechsler Preschool and Primary Scale of Intelligence). Children with a mean serum thyroxine level greater than 180 nmol/L (14 micrograms/dl) during the first year had a significantly higher Mental Development Index at 2 years and Verbal IQ at 6 years than children with serum thyroxine values less than 129 nmol/L (10 micrograms/dl). Boys had a lower Mental Development Index at 2 years of age than girls (86.9 vs 105.1; p less than 0.001) and a higher frequency of elevated serum levels of thyroid-stimulating hormone during the first year (p = 0.001). No signs of toxic effects of a high hormone level at the time of IQ assessment were detected. However, high serum levels of thyroxine at ages 2 to 4 years in girls were related to lower Performance IQ at age 6 years. The results demonstrate that the serum level of thyroxine is of importance in relation to intellectual development. Thyroxine levels above the upper reference range during the first 2 years were related to best intellectual development at 2 and 6 years.

Psychological development at 7 years of age in children with congenital hypothyroidism. Timing and dosage of initial treatment

Sixty of 68 consecutive patients detected during the first two years of the Swedish screening programme for congenital hypothyroidism were Griffiths tested at the age 6.5-7.5 years. The test quotients of the patients could not be distinguished from those of a reference population. Replacement therapy with 8.7 +/- 2.8 micrograms of L-thyroxine (mean +/- SD)/kg/d had been started at 15.0 +/- 7.1 days of life. Furthermore, normal results on Griffiths tests were also found in 13 patients with delayed normalization of serum TSH, i.e. greater than 19 mU/l at the age of six weeks, as well as in patients with retarded skeletal maturity and/or very low neonatal serum levels of thyroxine, i.e. less than 18 nmol/l and tri-iodothyronine, i.e. less than 0.92 nmol/l. Our findings indicate that a replacement dose of 6-11 micrograms L-thyroxine/kg/d is adequate and allows normal psychological development if treatment is started early.

Thyroid disease and pregnancy

Thyroid disease is common in younger women and may be a factor in reproductive dysfunction. This probably only applies to severe cases of hyper- or hypothyroidism. Once adequately treated, neither of these disorders significantly impacts on fertility. The key is to recognize and to treat thyroid disorders in the reproductive-age woman before conception. Thyroxine therapy and even antithyroid drug therapy should be continued during pregnancy as necessary. Pregnancy is a euthyroid state that is normally maintained by complex changes in thyroid physiology. The fetal and neonatal hypothalamic-pituitary-thyroid system develops independently, but it may be influenced by thyroid disease in the mother. Early pregnancy is characterized by an increase in maternal T4 secretion stimulated by hCG and an increase in TBG, resulting in the elevated total serum T4 in pregnancy. The debate continues as to whether maternal T4 is important in early or late fetal brain development. If so, the physiologic changes in thyroid hormone secretion and transport in early pregnancy would help to ensure that a sufficient amount of thyroid hormone was available. There is new evidence in human subjects that substantial maternal T4 can cross the placenta during pregnancy, and this may be particularly important when fetal thyroid function is compromised as a result of congenital hypothyroidism. Maternal and fetal/neonatal outcomes in pregnancy are adversely affected if severe hypothyroidism is undiagnosed or inadequately treated. Thyroid function tests should be obtained during gestation in women taking T4 and appropriate dose adjustments should be made for TSH levels outside a normal range. The TSH-receptor blocking antibodies from the mother are a recognized cause of congenital hypothyroidism in the fetus and neonate that can be permanent or transient. If neonatal hypothyroidism is detected through neonatal screening programs, and prompt and adequate T4 replacement therapy is instituted as soon as possible following delivery, subsequent growth and development are usually normal. Paradoxically, pregnancy often has a favorable effect on the course of maternal Hashimoto's disease, although there is the risk of relapse postpartum. Pathophysiologic conditions of hCG secretion such as gestational trophoblastic disease and hyperemesis gravidarum may present as thyrotoxicosis in pregnancy, but the main cause of this syndrome is Graves' disease. The mainstay of treatment is antithyroid drugs and either propylthiouracil or methimazole may be used safely. Subtotal thyroidectomy, after medical control, is the alternative treatment, but radioiodine ablation is contraindicated.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationship between maternal thyroxine levels during pregnancy and memory function in childhood

Two investigations are reported into the memory functions of a group of subjects for whom information on maternal thyroxine (T4) levels during pregnancy is available. The first study made when the subjects were aged 14-15 years examined forward and backward memory span. No relationship between maternal T4 levels and capacity of the short-term store, measured as length of forward memory span, was found. Backward memory span, which involves performing a mental operation on the material held in store, was found to be associated with maternal T4 level. The second study, made when the subjects were aged 16-17 years, found a relationship between maternal T4 levels during pregnancy and memory for serial position. Findings are discussed in terms of the role of maternal thyroxine in fetal brain development.

Elementary school performance of children with congenital hypothyroidism. New England Congenital Hypothyroidism Collaborative

The aim of this study was to determine whether hypothyroid children treated early as a result of diagnosis after neonatal screening progressed normally in school. The New England Congenital Hypothyroidism Collaborative studied 72 of its patients at the ages of 9 or 10 years after they had completed 3 years of schooling beyond kindergarten. Control subjects were 96 classmates of the same sex and age as the patients and 32 siblings of appropriate age for the testing. Intelligence quotients (IQs) were measured by the Wechsler Intelligence Scale for Children-Revised abbreviated to five items, and school achievement by the Peabody Individual Achievement Test. In addition, a series of neuropsychologic tests was administered to both patients and control subjects. Educational histories were obtained from the parents for 74 patients, 87 of their siblings, 96 classmates, and 96 siblings of the classmates. The IQ of the control subjects (mean +/- SEM) was 109 +/- 1.2 versus 106 +/- 1.4 for the patients. The mean overall achievement score was 109 +/- 0.93 for the control subjects and 108 +/- 1.3 for the patients. These differences are not statistically significant. The regression lines relating overall Peabody Individual Achievement Test scores or subtests thereof to IQ did not differ among the patients and the control groups. Within the groups the regression lines for IQ and the different subtests of school achievement were also identical. The percentages of children repeating a grade, needing extra tutoring, or in special classes were the same for patients and control groups. We conclude that children with hypothyroidism have no apparent specific impediments to learning unrelated to intelligence.