Neurophysiologic studies and cognitive function in congenital hypothyroid children

Congenital hypothyroidism and associated visual-motor and intellectual development

BACKGROUND

Congenital hypothyroidism's sequelae include visuomotor and intellectual developmental deficits. Visual-motor perception is a cognitive function related to academic performance. Intellect is the ability to learn and use acquired knowledge to solve and achieve goals. Our objective was to evaluate visual-motor and intellectual development in children with late initiation of treatment for congenital hypothyroidism enrolled in a developmental follow-up and intervention program.

METHODS

We evaluated the visual-motor and intellectual development of 75 infants with congenital hypothyroidism, 34 with athyrosis, and 41 with ectopia using the Bender Visual-Motor Development Test and the Weschler Intelligence Scale at eight and nine years of age.

RESULTS

Children with ectopia had a visual-motor delay of -2 years and an Intelligence Quotient (IQ) greater than 98 points. Children with athyrosis had a visual-motor delay equivalent to -3.2 years and an IQ below 90 points. Better performance on Bender's test was positively correlated with IQ. Attending more than 80% of Developmental Intervention Program appointments had a positive impact on intellectual development.

CONCLUSIONS

Timely diagnosis and early treatment with the appropriate dose of levothyroxine are determining factors; however, attendance to a development follow-up and intervention program could further support the cognitive development of children with congenital hypothyroidism.

IMPACT

Visuomotor development influences cognitive functions related to school performance. Deficits in the ability to learn and use acquired knowledge to solve problems and achieve goals are characteristic of children with congenital hypothyroidism. Delayed treatment is associated with more severe sequelae in both visual-motor and intellectual development. Here, we show that treatment with adequate doses of levothyroxine and inclusion in a follow-up and developmental program are highly recommended for patients with delayed treatment. A better understanding of these factors will allow clinicians to target therapeutic interventions.

Neuropsychological Alterations in Patients with Congenital Hypothyroidism Treated with Levothyroxine: Linked Factors and Thyroid Hormone Hyposensitivity

Eighty-five percent of the studies of patients with congenital hypothyroidism (CH) treated with Levothyroxine (L-T₄) report neuropsychological sequelae throughout life. In neonates and infants, there is a deficit in sensorimotor skills (impaired balance). In preschool and elementary school children and adolescents, there are alterations in intellectual quotient (low scores), language (delayed phonological acquisition), memory (visual, verbal, visuospatial, visuoconstructive, autobiographical, and semantic), sensorimotor skills (impaired fine and gross motor control), and visuoconstructive–visuospatial domain (low scores in spatial location, block design, and object assembly). These neuropsychological domains are also affected in young adults, except for language (adequate verbal fluency) and visuoconstructive–visuospatial domain (no data). The onset and severity of neuropsychological sequelae in patients with treated CH depend on several factors: extrinsic, related to L-T₄ treatment and social aspects, and intrinsic, such as severity and etiology of CH, as well as structural and physiological changes in the brain. In this review, we hypothesized that thyroid hormone hyposensitivity (THH) could also contribute to neuropsychological alterations by reducing the effectiveness of L-T₄ treatment in the brain. Thus, further research could approach the THH hypothesis at basic and clinical levels to implement new endocrinological and neuropsychological therapies for CH patients.

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.

Median nerve conduction velocity and central conduction time measured with somatosensory evoked potentials in thyroxine-treated infants with Down syndrome

OBJECTIVE

The aim of this study was to determine whether thyroxine treatment would improve nerve conduction in infants with Down syndrome.

METHODS

A single-center, nationwide, randomized, double-blind, clinical trial was performed. Neonates with Down syndrome were assigned randomly to thyroxine (N = 99) or placebo (N = 97) treatment for 2 years. Daily thyroxine doses were adjusted regularly to maintain plasma thyrotropin levels in the normal range and free thyroxine concentrations in the high-normal range. The outcome measures were nerve conduction velocity and central conduction time, determined through median nerve somatosensory evoked potential recording, at the age of 24 months.

RESULTS

At the age of 24 months, somatosensory evoked potential recordings for 81 thyroxine-treated and 84 placebo-treated infants were available for analysis. Nerve conduction velocity and central conduction time did not differ significantly between the 2 treatment groups (nerve conduction velocity: thyroxine: 51.0 m/second; placebo: 50.1 m/second; difference: 0.9 m/second; central conduction time: thyroxine: 8.83 milliseconds; placebo: 8.73 milliseconds; difference: 0.1 milliseconds).

CONCLUSIONS

Postnatal thyroxine treatment of infants with Down syndrome did not alter somatosensory evoked potential-measured peripheral or central nerve conduction significantly. The absence of favorable effects suggests that pathologic mechanisms other than mild postnatal hypothyroidism underlie the impaired nerve conduction. The absence of adverse effects suggests that longstanding plasma free thyroxine concentrations in the high-normal range are not harmful to nerve maturation.

Cognitive changes in short-term hypothyroidism assessed with event-related brain potentials

Hypothyroidism is a common clinical problem during (131)Iodine-therapy of thyroid cancer. In the present investigation, possible cognitive dysfunction during hypothyroid state was assessed by means of neuropsychological tests and the recording of event-related brain potentials (ERPs). Fifteen patients undergoing therapy for thyroid cancer were examined twice: (1) substituted with thyroid hormones, (2) during hypothyroid state immediately prior to treatment. Standard neuropsychological tests were applied during both sessions and subjects showed a mild-to-moderate impairment in their hypothyroid state. In addition, ERPs were recorded from 19 scalp sites while subjects performed two visual search tasks. The serial task required the effortful one-by-one scanning of several items within a visual array, while the parallel task allowed processing of all stimulus items in parallel and automatically. ERPs showed a marked amplitude decrement and delay of the P3 component known to index the speed of stimulus evaluation and the amount of available processing resources. This effect was present only for the serial search task, while no changes were seen in the parallel search task. These data show that hypothyroidism during (131)Iodine-therapy is associated with clinically relevant cognitive dysfunctions, especially with effortful attention demanding tasks.

Neuropsychological and psychosocial correlates of endocrine and metabolic disorders--a review

With advances in medical knowledge, many paediatric metabolic and endocrine disorders can now be treated effectively. The focus of clinical management has shifted from survival to quality of outcome for survivors. This paper refers to three conditions, congenital hypothyroidism, phenylketonuria and type 1 diabetes mellitus, to illustrate the effects of metabolic disturbances on the developing brain. Neuropsychological and psychosocial correlates of these disorders are reviewed. Current knowledge about illness-related predictors of outcome is also discussed.

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.

Congenital hypothyroidism in Wales (1982-1993): demographic features, clinical presentation and effects on early neurodevelopment

OBJECTIVE

Neonatal screening for congenital hypothyroidism (CH) was introduced in Wales in 1982. The aim of the study was to evaluate the demographic features and characteristics of infants identified during the first 12 years of screening and their neurodevelopmental progress in the first 2 years of life.

DESIGN

Prospective collection of biochemical and clinical data (including results of Griffiths Mental Development Scales) obtained from questionnaires sent to paediatricians responsible for the ongoing clinical care of children with CH.

PATIENTS

In Wales, between 1982 and 1993, 136 infants with primary congenital hypothyroidism (CH) were identified by the neonatal screening programme.

RESULTS

Of all new-borns, 99.8% were screened and the prevalence of CH was 1 in 3279 (1 in 2473 girls and 1 in 4770 boys). The prevalence of CH was increased in North Wales. CH was associated with increased birth weight (48.5% of infants weighed greater than 3.5 kg) and an increased prevalence of non-thyroidal congenital abnormalities (8%) and congenital heart disease (3%). Isotope scanning demonstrated an increased prevalence of normal or enlarged thyroid glands and fewer ectopic glands compared to those reported in other studies. The mean developmental quotients (DQs) for individual subsets of intellectual and behavioural functioning in children with CH aged 1 and 2 years were all above 100 (range: 103.5-111.9). In subjects with absent thyroids, these DQs were correlated with the serum concentrations of free thyroxine before treatment.

CONCLUSIONS

The demographic features of infants with congenital hypothyroidism born in Wales are similar to those reported from other European studies although there are marked regional variations in prevalence within Wales for which there is no apparent explanation. The median age of starting therapy was 17 days and compares favourably with other screening programmes. The overall mental development of Welsh children aged 1 and 2 years with congenital hypothyroidism identified by neonatal screening is satisfactory.