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Query: UMLS:C0025362 (mental retardation)
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It is well known that insufficient production of thyroid hormones during the fetal and neonatal period of development may result in permanent brain damage unless treatment with thyroid hormone is instituted very soon after birth. But congenital hypothyroidism is not the only situation in which brain damage may be related to insufficient thyroid function. Cretinism is the most severe manifestation of iodine deficiency disorders found in areas where iodine intake is greatly reduced. Some of the manifestations of cretinism suggest that the insult to the developing brain starts earlier than in the case of congenital hypothyroidism. Hypothyroxinemia of mothers with adequate iodine intake may also leave permanent, though less severe, mental retardation. For these reasons the possible role of maternal transfer of thyroid hormones during early fetal development have been reinvestigated, using the rat to obtain various experimental models. It has been shown that thyroid hormones are found in embryonic tissues before onset of fetal thyroid function and that thyroidectomy of the mother results in delayed development of the concepta. The concentrations of T4 and T3 in embryonic tissues from thyroidectomized dams were undetectable before the onset of fetal thyroid function, and still reduced in some tissues near term, despite the onset of fetal thyroid function. Treatment of control and thyroidectomized dams with methyl-mercaptoimidazole to block fetal thyroid function reduced thyroid hormone concentrations in fetal tissues near term, but this decrease could be partially avoided by infusion of physiological doses of thyroxine to the mothers. Iodine deficiency of the mothers resulted in thyroid hormone deficiency of the developing embryo, which was very marked until term in all tissues including the brain. The results strongly support a role of maternal thyroid hormones in fetal thyroid hormone economy both before and after the onset of the fetal thyroid function, at least in the rat. They also support a role of the hypothyroxinemia of iodine-deficient mothers in initiating the brain damage of the endemic cretin, a damage which would not be corrected once the fetal thyroid becomes active, as iodine-deficiency of the fetus would impair adequate production of hormones by its own thyroid, and maternal transfer would continue to be low.
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PMID:Fetal and maternal thyroid hormones. 329 61

This work reports the presence of endemic cretinism in a small district located inside an endemic goiter area in north-eastern Sicily, personally described. The study covers 19 mental defectives (11 females and 8 males, mean age 35.8 +/- 15.5 yr) selected on the basis of severe mental retardation recognized by the local doctors. No systematic survey for cretinism was carried out in the total population. Marked mental retardation was evident in all subjects. Nine of them exhibited clinical and biochemical signs of hypothyroidism (myxedematous cretins). The 10 others were clinically euthyroid and had deaf-mutism and/or pyramidal tract dysfunction (neurological cretinism). Familial aggregation of cretinism was also observed. In both myxedematous and neurological cretins and urinary iodine excretion was very low, but not significantly different from that recorded in the euthyroid controls of the same area. The data available do not clarify the pathogenesis of endemic cretinism in Sicily. However, the marked height retardation, the observation of delayed bone maturation and the severity of mental deficiency suggest that thyroid failure was present in early life. The presence of endemic cretinism today in Sicily constitutes a strong argument in favour of the immediate introduction of adequate iodine prophylaxis.
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PMID:Endemic cretinism in Sicily. 732 Apr 34

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

Nutrition programs and family planning programs have a mutual impact on each other and nutrition and family planning services can be provided in an integrated program; however, an integrated approach is not absolutely necessary as individual programs can also be beneficial. Reductions in population growth and family size can contribute toward inproving nutritional standards by increasing the available per capita food supply. Nutritional programs can promote family planning by reducing infant and child mortality. The proportion of the population in developing countries suffering from malnutrition ranges from 25%-75%. Major nutritional problems are anemia caused by iron and folate deficiency, goiter caused by iodine deficiency, and blindness caused by Vitamin A deficiency. Severe clinical malnutrition gives rise to pellegra, beriberi, and other serious disease which can be easily recognized and diagnosed. Only 2-3% of a poorly fed population suffers from severe clinical malnutrition. Most of the individuals in a poorly fed population suffer milder forms of malnutrition which are harder to diagnose. During the 1st stage of malnutrition body stores of needed materials decline. There are no outward clinical manifestations of this decline and the problem can be detected only through biochemical measurement. During later stages as organ dysfunction, tissue damage, and irreversible damage occurs the clinical signs become increasing apparent. The effects of poor nutrition on children include 1) reduced growth rates; 2) impairment of the body's defense system for fighting infection; and 3) mental retardation. The effects of poor nutrition on adults are more difficult to identify, but a number of studies indicate that work output is significantly decreased by malnutrition.
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PMID:Nutrition policies and population policies. 746 17

Iodine is a trace element present in the human body in minute amounts (15-20 mg in adults, i.e. 0.0285 x 10(-3)% of body weight). The only confirmed function of iodine is to constitute an essential substrate for the synthesis of thyroid hormones, tetraiodothyronine, thyroxine or T4 and triiodothyronine, T3 (1). In thyroxine, iodine is 60% by weight. Thyroid hormones, in turn, play a decisive role in the metabolism of all cells of the organism (2) and in the process of early growth and development of most organs, especially of the brain (3). Brain development in humans occurs from fetal life up to the third postnatal year (4). Consequently, a deficit in iodine and/or in thyroid hormones occurring during this critical period of life will result not only in the slowing down of the metabolic activities of all the cells of the organism but also in irreversible alterations in the development of the brain. The clinical consequence will be mental retardation (5). When the physiological requirements of iodine are not met in a given population, a series of functional and developmental abnormalities occur (Table 1), including thyroid function abnormalities and, when iodine deficiency is severe, endemic goiter and cretinism, endemic mental retardation, decreased fertility rate, increased perinatal death, and infant mortality. These complications, which constitute an hindrance to the development of the affected population, are grouped under the general heading of Iodine Deficiency Disorders, IDD (6). Broad geographic areas exist in which the population is affected by IDD.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Iodine deficiency in Europe. 771 23

This paper reviews present knowledge on the etiology, pathophysiology, complications, prevention, and therapy of the disorders induced by iodine deficiency. The recommended dietary allowances of iodine are 100 micrograms/day for adults and adolescents, 60-100 micrograms/day for children aged 1 to 10 years, and 35-40 micrograms/day in infants aged less than 1 year. When the physiological requirements of iodine are not met in a given population, a series of functional and developmental abnormalities occur including thyroid function abnormalities and, when iodine deficiency is severe, endemic goiter and cretinism, endemic mental retardation, decreased fertility rate, increased perinatal death, and infant mortality. These complications, which constitute a hindrance to the development of the affected populations, are grouped under the general heading of iodine deficiency disorders (IDD). At least one billion people are at risk of IDD. Iodine deficiency, therefore, constitutes one of the most common preventable causes of mental deficiency in the world today. Most of the affected populations live in mountainous areas in preindustrialized countries, but 50 to 100 million people are still at risk in Europe. The most important target groups to the effects of iodine deficiency from a public health point of view are pregnant mothers, fetuses, neonates, and young infants because the main complication of IDD, i.e., brain damage resulting in irreversible mental retardation, is the consequence of thyroid failure occurring during pregnancy, fetal, and early postnatal life. The main cause of endemic goiter and cretinism is an insufficient dietary supply of iodine. The additional role of naturally occurring goitrogens has been documented in the case of certain foods (milk, cassava, millet, nuts) and bacterial and chemical water pollutants. The mechanism by which the thyroid gland adapts to an insufficient iodine supply is to increase the trapping of iodide as well as the subsequent steps of the intrathyroidal metabolism of iodine leading to preferential synthesis and secretion of triiodotyronine (T3). They are triggered and maintained by increased secretion of TSH, which is ultimately responsible for the development of goiter. The acceleration of the main steps of iodine kinetics and the degree of hyperstimulation by TSH are much more marked in the pediatric age groups, including neonates, than in adults, and the development of goiter appears as an unfavorable side effect in the process of adaptation to iodine deficiency during growth. The most serious complication of iodine deficiency is endemic cretinism, a syndrome characterized by irreversible mental retardation together with either a predominant neurological syndrome or predominant hypothyroidism, or a combination of both syndromes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The disorders induced by iodine deficiency. 805 57

Following the 1990 World Summit for Children, the annual report of UNICEF detailed progress to the Summit's goals it set for the year 2000. The targets are a 33% reduction in under-5 mortality, halving child malnutrition and maternal mortality rates, and 90% immunization coverage of major childhood diseases. Over 85 states are signed up with national programs to mobilize not only health services but to extend it to schools, media, religious leaders, and businesses. The maternal mortality rate of 1 in 20 in Africa compares with 1 in 3600 in North America; and under-5 mortality rates of 5 in 1000 in Sweden are compared with 300/1000 in Niger. 61 countries are still likely to double their population in the next 35 years, and millions of women have no access to birth control programs. Mental retardation caused by lack of iodine in the diet claims an estimated 6 million victims. There are also the familiar problems created by diarrhea, measles, and bottle feeding. On the other hand, the new UNICEF report, The Progress of Nations, demonstrates that in little more than 1 generation average real incomes have doubled; child death rates have halved; malnutrition has fallen by about 30% (only 1 or 2% of the world's children are affected by visible malnutrition); life expectancy has increased by about 33%; modern contraceptive use by couples has risen from less than 10% to over 50% since 1960; and average family size is declining in almost every country. In just a decade measles immunization coverage of the developing world's children has risen from 20% to 80% saving 3 million young lives a year and preventing 50 million other children from catching a nonfatal dose. Nevertheless, these gains are thwarted by the existence of millions of malnourished and uneducated children whose prospects for future employment are constrained by polio, blindness, deafness, and mental retardation.
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PMID:UNICEF's goals for 2000 AD. 810 79

The patient was a 17 year-old-boy with mental retardation and cerebral palsy, who underwent tracheostomy because of tracheobronchomalacia and tongue swallowing three months ago. After minimal tracheostomy bleeding was noted for a few days, massive hemorrhage occurred suddenly. The patient was severely hypotensive. The cuff on the tracheostomy tube was hyperinflated, which stopped the bleeding temporarily. Through a median sternotomy and collar incision, a pin hole-sized defect in the medial surface of the brachiocephalic artery at the tracheal balloon was repaired by suture. The tracheal defect allowed visualization of the tracheal cannula balloon. The pectoralis major muscle flap was interposed between the tracheal defect and the artery. The tracheal defect was packed with muscle. Seven days after the operation, the second operation was done for recurrent bleeding. The defective segment of brachiocephalic artery was resected and the ends were oversewn with monofilament sutures. Continuous irrigation with povidone-iodine solution was continued for purulent mediastinitis. We believe that interruption of blood flow of the brachiocephalic artery, interposition and packing of muscle flap over the tracheal defect and continuous irrigation for infection were effective treatment of choice.
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PMID:[A case report of surgically treated tracheobrachiocephalic artery fistula following tracheostomy]. 837 14

Normal development of the CNS requires adequate thyroid hormone exposure. Since iodine is an essential component of the thyroid hormone molecule, its deficiency during fetal development can cause hypothyroidism and irreversible mental retardation. The full-blown syndrome, called cretinism, includes deaf-mutism, short stature, spasticity, and profound mental retardation. The clinical spectrum can vary in degree and combination of these features. Screening programs in iodine-deficient countries show that up to 10% of neonates have elevated serum TSH levels, putting them at theoretical risk for permanent brain damage. About one billion people worldwide risk the consequences of iodine deficiency, all of which can be prevented by adequate maternal and infant iodine nutrition. Iodized salt is usually the preferred prophylactic vehicle, but iodized vegetable oil, iodized water, and iodine tablets are also occasionally used. The United Nations and the heads of state of most countries have pledged the virtual elimination of iodine deficiency by the year 2000. This goal is technically feasible if pursued with sufficient vigor and resources.
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PMID:Iodine supplementation and the prevention of cretinism. 849 59

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


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