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

Severe iodine deficiency may lead to endemic cretinism, which is characterized by a number of abnormalities, such as mental retardation, neurological abnormalities and hearing disorders. These abnormalities may occur in various combinations, but impaired mental development is always a component. The present study was attempted to determine whether there is also evidence of mental retardation, perhaps to a lesser degree, in that part of the population that manifest no symptoms of cretinism, the non-cretins, in an iodine-deficient area. Results of an extensive test battery have been collected in two village populations: one village in an area with severe iodine deficiency and a control village in a non-iodine-deficient area. Both villages were situated in Central Java, Indonesia. In the selected villages the total population between the ages of 6 and 20 years participated in this study. No evidence of significant mental retardation has been detected in the non-cretin group in the severely iodine-deficient area. Significant differences between the two populations, however, have been found with regard to a number of perceptual and neuro-motor abilities.
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PMID:Effects of iodine deficiency on mental and psychomotor abilities. 741 50

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

Thyroid hormones are essential for normal behavioral, intellectual, and neurological development. Congenital hypothyroidism, if not treated, can result in irreversible mental retardation, whereas thyroid diseases with more moderate impairment of thyroid function, such as resistance to thyroid hormone, cause less severe intellectual and behavioral abnormalities, including attention deficit hyperactivity disorder. There is increasing evidence that exposure to certain synthetic compounds, including dioxins and polychlorinated biphenyls (PCBs), during the perinatal period can also impair learning, memory, and attentional processes in offspring. Animal and human studies suggest that exposure to these environmental toxicants impair normal thyroid function. Although the precise mechanisms of action of the adverse effects these toxicants have on neurodevelopment have not yet been elucidated, it is possible that they are partially or predominantly mediated by alterations in hormone binding to the thyroid hormone receptor. The convergence of studies that examine the neurodevelopmental consequences of moderate impairment of thyroid function, such as is found in resistance to thyroid hormone, with those studies that demonstrate the adverse behavioral and cognitive effects of perinatal exposure to dioxins and PCBs serves to generate new hypotheses to test in a research setting. Such studies may provide new insights into the basic pathogenesis of developmental neurotoxicity following exposure to thyroid-disrupting synthetic compounds.
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PMID:Resistance to thyroid hormone: implications for neurodevelopmental research on the effects of thyroid hormone disruptors. 946 Jan 71

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

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

Congenital hypothyroidism occurs in 1:4000 newborns. Mass screening for congenital hypothyroidism constitutes a major progress in the prevention of mental retardation. The neonatal screening programme in Poland was established and implemented by the National Research Institute of Mother and Child from the middle of the 70. and reorganised in 1997. Recall examinations in the infants, substitute therapy with l-thyroxine and the follow-up of hypothyroid infants and children are presented.
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PMID:[A model for clinical diagnosis-treatment of the newborn with an abnormal screening test for hypothyroidism and in children with congenital hypothyroidism]. 1122 4

Congenital hypothyroidism is one of the most common diseases in paediatric endocrinology. Thyroid hormones are essential in brain development, which takes place during foetal life and early postnatal life up to the 2nd year of age. The main etiologic factors of congenital hypothyroidism are anomalies of development, function and regulation of the thyroid gland. Clinical signs of thyroid hormone deficiency in infants are non-specific. Early diagnosis is based on newborn screening for congenital hypothyroidism, which was started in Poland in 1977. Treatment within the first days of life with appropriate dosage of thyroxine prevents mental retardation. This paper summarises current knowledge on congenital hypothyroidism in children.
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PMID:[Congenital hypothyroidism]. 1122 3

This editorial reviews the impact of iodine deficiency (1) on thyroid function in pregnant women and neonates and (2) on the neurointellectual development of infants and children. All degrees of iodine deficiency (mild: iodine intake of 50-99 microg/day, moderate: 20-49 microg/day, and severe: <20 microg/day) affect thyroid function of the mother and the neonate as well as the mental development of the child. The damage increases with the degree of the deficiency, with overt endemic cretinism as the severest consequence. Maternal hypothyroxinaemia during early pregnancy is a key factor in the development of the neurological damage in the cretin. Selenium deficiency combined with iodine deficiency partly prevents the neurological damage but precipitates severe hypothyroidism in cretins. Iodine deficiency results in a global loss of 10-15 IQ 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:Iodine deficiency as a cause of brain damage. 1126 81

Congenital hypothyroidism is the most prevalent endocrine disorder in the newborn and affects 1 in 3000-4000 newborns. Screening for congenital hypothyroidism is a major achievement of paediatrics because early diagnosis and treatment have resulted in normal development in nearly all cases. The cause of congenital hypothyroidism in the majority of newborns is unknown. However, in some patients the molecular basis of their congenital hypothyroidism has recently been clarified. In patients with congenital hypothyroidism and a normally developed thyroid gland, the autosomal recessive inheritance of loss-of-function mutations of genes encoding for the thyroid peroxidase gene, the sodium-iodide symporter gene and the pendrin gene have been identified. The autosomal recessive inheritance of loss-of-function mutations of the thyroid stimulating hormone (TSH) receptor as well as the dominant inheritance of mutations encoding for transcription factors have been identified in patients with defective thyroid development. Furthermore, it has become evident that in some patients with persistent mental retardation and neurological symptoms, defects of the transcription factor NKX2.1, which is expressed in the thyroid gland as well as in the CNS during embryonic development, cause both defective thyroid and CNS development resulting in persistent neurological and mental defects despite early diagnosis and treatment. Central hypothyroidism is a rare disease with an estimated frequency of not more than 1 in 50000 newborns. Central hypothyroidism can be due to recessive inheritance of loss-of-function mutations of the TSH-beta gene and to developmental defects of the hypothalamus or pituitary. In contrast to the previous assumption that isolated TSH deficiency will not lead to impaired mental development, identification of the molecular defects in central hypothyroidism has clearly demonstrated that some of these patients will have impaired mental development. Clarification of the molecular defects of thyroid development will help to explain the differences in outcome in patients with congenital hypothyroidism and to develop new diagnostic and therapeutic strategies to ensure adequate counselling and care for these patients.
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PMID:Neonatal thyroid disorders. 1256 17

Congenital hypothyroidism (CH) is a neonatal disorder that is caused by a prolonged loss of thyroid hormone, which is essential for early brain development. While CH was once the leading cause of mental retardation, newborn screening for CH now allows for early identification and treatment. As a result, affected children now show normal physical and psychological development. Nevertheless, because they still undergo a brief but circumscribed period of thyroid hormone insufficiency, they are at risk for subtle selective impairments. This paper examines several of the persisting deficits observed in children with CH that was identified early in life by newborn screening as well as the relevant disease- and treatment-related factors contributing to such deficits. Highlighted will be (a) a weakness in visuospatial processing, which is associated with prenatal thyroid hormone insufficiency, (b) selective memory deficits associated with postnatal thyroid hormone insufficiencies, (c) a weakness in sensorimotor abilities also reflecting postnatal thyroid hormone insufficiencies, and (d) attention deficits, which are due to abnormal thyroid hormone levels at time of testing. Because these four disabilities implicate different neural substrates, the findings described presently will provide insights as to the specific time windows when different brain structures in the human critically need thyroid hormone.
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PMID:Congenital hypothyroidism: an analysis of persisting deficits and associated factors. 1275 31


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