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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Congenital hypothyroidism (CH) is the most common cause of preventable mental retardation. Thyroid hormone deficiency in utero and in the first neonatal months is responsible for permanent damage. While foetal hypothyroidism is at present unavoidable, earlier diagnosis and initiation of treatment in neonates with CH is important and highly recommended. At the moment, the Italian screening program for CH allows diagnosis and treatment within the first month of life. In Italy, screening programs became obligatory only a short time ago. In some regions, they started a few years ago, whereas in others they have been carried out only in an irregular way and only a part of the population has been investigated. Therefore CH was diagnosed just on the basis of clinical signs, with a consequent delay in the initiation of substitutive therapy. We describe the case of a little girl with CH diagnosed when she was three years old. We report the results of this case follow-up study and we describe the features of her neuropsychological development to point out her improvement and permanent disorders. The little girl was clearly hypothyroid with delayed achievement at three, but with pharmacological treatment she showed a dramatic amelioration in growth, language, motor skills and cognitive performances.
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PMID:[Missed diagnosis: a case of congenital hypothyroidism treated after three years]. 913 64

Systematic screening for congenital hypothyroidism in the neonate constitutes a major progress in the prevention of mental retardation, as the condition occurs in 1/4,000 newborns and necessarily results in brain damage if not properly detected and treated during the first days of life. Screening and diagnostic and therapeutic procedures are discussed, as well as outcome and prognosis of the affected infants. Primary thyroid-stimulating hormone screening is almost universally recommended. Early therapy (within 14 days) with appropriate doses of thyroxine (about 10 micrograms/kg/day) will prevent any brain damage even in case of evidence of fetal hypothyroidism, as thyroxine of maternal origin will reach the fetus and largely protect him. Neonatal thyroid screening is also a particularly sensitive monitoring tool in the evaluation of the effects and of the correction of iodine deficiency at the population level.
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PMID:Neonatal screening for congenital hypothyroidism: results and perspectives. 925 21

Nineteen cases of duplication of segments of the long arm of chromosome X have been published in 13 males and in 6 females. We report an additional case of a male with growth and mental retardation, growth hormone deficiency, compensated primary hypothyroidism, distinctive anomalies of the face, hypoplastic genitalia, and hypotonia in whom inverted duplication of a segment in the long arm of X chromosome was diagnosed, 46,Y, dup (X)(q21.2q13.3), and mosaicism was demonstrated in his mother's X chromosome. The rearranged segment was diagnosed utilizing high resolution G-band technique and FISH studies, using chromosome X total chromosome probe and DNA XIST probe. This appears to be the first report of a patient with duplication of Xq and hypothyroidism.
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PMID:Inherited inverted duplication of X chromosome in a male: report of a patient and review of the literature. 937 22

We present two unrelated children, a male and a female, with signs of ectodermal dysplasia, mental retardation, agenesis/ dysgenesis of the corpus callosum, and primary hypothyroidism. Reports of ectodermal dysplasia with CNS malformations or hypothyroidism or both are rare. We suggest that the condition we describe is a distinct entity within the large group of ectodermal dysplasia syndromes and that it has a variable clinical spectrum. As both males and females are affected and in a few reports some parents show minimal signs, the inheritance is likely to be autosomal dominant.
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PMID:Ectodermal dysplasia, primary hypothyroidism, and agenesis of the corpus callosum: variable expression of a single syndrome? 950 98

Mental retardation is a prominent feature of many neurodevelopmental syndromes. In an attempt to identify genetic components of these illnesses, we isolated and sequenced a large number of human genomic cosmid inserts containing large trinucleotide repeats. One of these cosmids, Cos-4, maps to the X-chromosome and contains the sequence of a 7.3-kb mRNA. Initial polymorphism analysis across a region of repetitive DNA in this gene revealed a rare 12-bp exonic variation (<< 1% in non-iII males) having an increased prevalence in non-Fragile X males with mental retardation (4%, P < 0.04, n = 81). This variant was not present in the highly conserved mouse homologue that has 100% amino acid identity to the human sequence near the polymorphism. Subsequent screening of two additional independent cohorts of non-Fragile X mentally retarded patients and ethnically matched controls demonstrated an even higher prevalence of the 12-bp variant in males with mental retardation (8%, P < 0.0003, n = 125, and 14%, P < 0.10, n = 36) vs the controls. Multivariate analysis was conducted in an effort to identify other phenotypic components in affected individuals, and the findings suggested an increased incidence of histories of hypothyroidism (P < 0.001) and treatment with antidepressants (P < 0.001). We conclude that the presence of this 12-bp variant confers significant susceptibility for mental retardation.
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PMID:Association of an X-chromosome dodecamer insertional variant allele with mental retardation. 970 38

Congenital hypothyroidism is a common preventable cause of mental retardation. The overall incidence is approximately 1:4000; females are affected about twice as often as males. Approximately 85% of cases are sporadic, while 15% are hereditary. The most common sporadic etiology is thyroid dysgenesis, with ectopic glands more common than aplasia or hypoplasia. While the pathogenesis of dysgenesis is largely unknown, some cases are now discovered to be the result of mutations in the transcription factors PAX-8 and TTF-2. Loss of function mutations in the thyrotropin (TSH) receptor have been demonstrated to cause some familial forms of athyreosis. The most common hereditary etiology is the inborn errors of thyroxine (T4) synthesis. Recent mutations have been described in the genes coding for the sodium/iodide symporter, thyroid peroxidase (TPO), and thyroglobulin. Transplacental passage of a maternal thyrotropin receptor blocking antibody (TRB-Ab) causes a transient form of familial congenital hypothyroidism. The vast majority of infants are now diagnosed after detection through newborn screening programs using a primary T4-backup TSH or primary TSH test. Screening test results must be confirmed by serum thyroid function tests. Thyroid scintigraphy, using 99mTc or 123I, is the most accurate diagnostic test to detect thyroid dysgenesis or one of the inborn errors of T4 synthesis. Thyroid sonography is nearly as accurate, but it may miss some cases of ectopic glands. If maternal antibody-mediated hypothyroidism is suspected, measurement of maternal and/or neonatal TRB-Ab will confirm the diagnosis. The goals of treatment are to raise the serum T4 as rapidly as possible into the normal range, adjust the levothyroxine dose with growth to keep the serum T4 (or free T4) in the upper half of the normal range and the TSH normal, and maintain normal growth and development while avoiding overtreatment. An initial starting dose of 10-15 microg/kg per day is recommended; this dose will decrease on a weight basis over time. Serum T4 (or free T4) and TSH should be monitored every 1-2 months in the first year of life and every 2-3 months in the second and third years.
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PMID:Congenital hypothyroidism: etiologies, diagnosis, and management. 1044 22

Although mental retardation associated with congenital hypothyroidism (CH) is prevented by newborn screening and early treatment, affected children still undergo a brief period of thyroid hormone deficiency reflecting etiology of thyroid disease, illness severity, and treatment factors. Because thyroid hormone is essential for normal brain development and because some processes require thyroid hormone in the period when thyroid hormone was lacking, children with CH treated early may still have subtle neurocognitive deficits. As the period when thyroid hormone is needed differs for different brain regions, there may be different types of deficits depending on when thyroid hormone levels were insufficient. Since 1980, we have been following a large cohort of Toronto-based children with congenital hypothyroidism identified by newborn screening from infancy to adolescence. Early findings revealed a 5-10-point decline in IQ, poorer visuomotor and visuospatial abilities, delayed speech and language development, selective neuromotor deficiencies, and poorer attention and memory skills, which were correlated with different disease and treatment factors. Now a comparison between 48 subjects at adolescence and matched controls indicates that deficits persist in visuospatial, memory, and attention domains and these are correlated with severity of early hypothyroidism. Negative relationships between attention indices and thyroxine (T4) elevations at time of testing also suggest a role for thyroid hormone in the regulation of attention.
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PMID:Congenital hypothyroidism: long-term outcome. 1044 23

All 50 states and the District of Columbia conduct newborn screening (NBS) programs that annually screen approximately 4 million infants for metabolic and other disorders to prevent mental retardation, disability, and death. In 1998, Georgia newborns were screened for eight disorders: phenylketonuria, galactosemia, tyrosinemia, homocystinuria, hypothyroidism, maple syrup urine disease, congenital adrenal hyperplasia, and sickle cell disease. Appropriate data that reflect progress toward achieving short- and long-term goals are necessary to assess the effectiveness of NBS and to inform public health policy decisions about which disorders to add or delete from screening. This report summarizes findings from an evaluation of data systems for metabolic and endocrine disorders in the Georgia NBS program and assesses the ability to measure progress toward short- and long-term goals. Although the data indicate that the program typically received specimens of sufficient quality for testing in a timely manner, additional data are needed to assess fully the effectiveness of the NBS program in identifying disorders.
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PMID:Evaluating newborn screening program data systems--Georgia, 1998. 1063 98

Despite significant progress in the last decades, endemic goiter remains a serious public health problem in the developing world, especially in Africa. Even in countries that have successfully reduced overall incidence to acceptable levels, endemic areas often remain. This persistence is due to the inadequacy of preventive measures and poor follow-up of control programs. The main etiologic factor in endemic goiter is inadequate dietary intake of iodine. This commonly occurs in communities depending exclusively on local produce grown on iodine-poor land, especially in mountain areas. Endemic goiter is epidemiologically associated with cretinism, deaf-mutism, and mental retardation. Even mild iodine deficiency leads to clinical hypothyroidism and moderate myxoedema with significantly reduced intellectual performance. Prevention of endemic goiter depends mainly on increasing the iodine intake of people in endemic areas. When iodine intake reaches the estimated adult minimum requirement (100 to 150 micrograms per day), the prevalence of goiter decreases. Two approaches have been used to increase iodine intake. The first consists of adding iodine to food staples such as table salt. The second consists of medical treatment using agents such as iodized oil. Iodization or iodination of salt is the most widespread and cost-effective method of prevention. Administration of iodized oil has been used only in severely endemic areas and in regions where reliable provision of iodinized salt is prevented by geographical barriers or political factors. However, iodized oil has been helpful in the start-up phase of prevention programs using iodized salt, either as an emergency measure or as a mean of convincing officials of the efficacy of iodine prophylaxis.
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PMID:[Management strategies for endemic goiter in developing countries]. 1081 56

I is required for the synthesis of thyroid hormones. These hormones, in turn, are required for brain development, which occurs during fetal and early postnatal life. The present paper reviews the impact of I deficiency (1) on thyroid function during pregnancy and in the neonate, and (2) on the intellectual development of infants and children. All extents of I deficiency (based on I intake (microgram/d); mild 50-99, moderate 20-49, severe > 20) affect the thyroid function of the mother and neonate, and the mental development of the child. The damage increases with the extent of the deficiency, with overt endemic cretinism as the severest consequence. This syndrome combines irreversible mental retardation, neurological damage and thyroid failure. Maternal hypothyroxinaemia during early pregnancy is a key factor in the development of the neurological damage in the cretin. Se deficiency superimposed on I deficiency partly prevents the neurological damage, but precipitates severe hypothyroidism in cretins. I deficiency results in a global loss of 10-15 intellectual quotient points at a population level, and constitutes the world's greatest single cause of preventable brain damage and mental retardation.
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PMID:The role of iodine in brain development. 1082 76


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