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

Thyroid hormone deficiency is frequently associated with central nervous system (CNS) disturbances such as mental retardation, convulsions, coma etc. Studies of quantitative changes in CNS in hypo- or hyperthyroidism are scarce. Evoked potentials is a good method of assessing the electrical response of the brain to different (visual, acoustic, somatosensory) stimuli and has been used extensively in the study of brain disturbances and to a lesser degree in metabolic diseases. We studied the visual evoked potentials (latency and amplitude) in 12 patients with hyperthyroidism and 15 patients with hypothyroidism, before treatment and after they became euthyroid. Four of the hyperthyroids (33%) had abnormally prolonged (> 104 msec) latencies before therapy. Two of them had clinical exophthalmos. No change was observed after euthyroidism was achieved. On the contrary 7 out of 15 (47%) hypothyroids had abnormally prolonged latencies which became normal in 4 when euthyroidism was achieved. Amplitude was lower than normal in 6 and became normal only in one of them after treatment. None of the hyperthyroid patients had amplitude changes. In conclusion, hypothyroid patients may have changes in the amplitude and/or the latency of visual evoked potentials which are reversible to a great extent with thyroxine. Evoked potentials is another method of studying in humans the metabolic effects of thyroxine deficiency in CNS.
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PMID:Visual evoked potentials in hypothyroid and hyperthyroid patients before and after achievement of euthyroidism. 149 Nov 23

A large prospective study investigated prenatal and perinatal antecedents of chronic motor dysfunction (cerebral palsy [CP]), evaluating approximately 400 characteristics of the mothers, pregnancies, or deliveries. In addition to confirming some, but not all, of the classic risk factors for CP, this study observed relatively large increases in the CP rate in association with maternal mental retardation, seizure disorders, hyperthyroidism, or with the administration of thyroid hormone and estrogen in pregnancy. Some risk factors were predictive of CP only insofar as they were associated with low birth weight or low Apgar scores. Among factors not significantly related to CP rate were maternal age, parity, socioeconomic status, smoking history, maternal diabetes, first trimester vaginal bleeding, kidney or bladder infection, moderate hypertension, long cord, use of anesthetic agents, or use of oxytoxics for initiation or augmentation of labor. Duration of labor, whether precipitate or prolonged, was not a risk factor for CP.
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PMID:Antecedents of cerebral palsy. I. Univariate analysis of risks. 403 90

A male patient born to a mother who developed rubella during the tenth week of gestation presented a typical congenital rubella syndrome with mental retardation, neuro-sensory deafness, hypoplasia of the dental enamel and chorioretinitis. Hyperthyroidism occurred at the age of 3 10/12 years and was treated successfully with propylthiouracil for 4 years. The course was complicated by premature craniosynostosis and a craniectomy was performed at the age of 7 years. Overt diabetes mellitus developed at 17 years and was well controlled by insulin therapy. Histocompatilibity (HLA) antigens were A2, B8, B40. Diabetes mellitus and thyroid disorders have previously been reported after congenital rubella, and recently after congenital cytomegalovirus infection. Our patient had both endocrinopaties. It is possible that HLA B8 antigens might be responsible for increased susceptibility to rubella infection.
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PMID:Hyperthyroidism, diabetes mellitus and the congenital rubella syndrome. 736 31

Congenital hyperthyroidism is a very rare disease. But, for each affected child it has to be considered as a serious condition because of the negative impact of hyperthyroidism on fetal and postnatal development. If the manifestation occurs during fetal life tachycardia, cardiac arrhythmia, growth retardation and, most significant, prematurity are the consequences. Postnatal signs of hyperthyroidism are irritability, tachycardia, hypertension, poor weight gain and thyroid enlargement. Even cardiac failure may occur if hyperthyroidism is severe and treatment not adequate which explains the high early mortality rate of 16%. The main complication of persistent hyperthyroidism in the neonatal period and during infancy is craniosynostosis. Severe developmental delay or even mental retardation can be the consequence of inadequate high T4-levels during fetal and neonatal life. Congenital hyperthyroidism was first recognized in infants born to mothers with Graves' disease. The description of transplacental passage of the maternal thyroid stimulating antibodies elucidated the molecular mechanism in this major group of patients with "autoimmune congenital hyperthyroidism". In contrast to this transient, self-limited character of "autoimmune congenital hyperthyroidism", due to the clearance of maternal antibodies from the infant's circulation, some cases of persistent congenital hyperthyroidism without signs of thyroid autoimmunity have been recognized. Activating mutations in the thyroid-stimulating hormone receptor were described recently as the underlying molecular pathogenesis in this group of "non-immune congenital hyperthyroidism". Therefore the possibility of a molecular differential diagnosis of both groups of congenital hyperthyroidism now exists and opens the opportunity of optimal treatment for each patient.
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PMID:Congenital hyperthyroidism. 943 7

In 1990, iodine deficiency affected almost one-third of the world population and was the greatest single cause of preventable brain damage and mental retardation. Following a resolution adopted by the World Summit for Children in 1990. major programmes of iodine supplementation were implemented by the governments of the affected countries with the support of major donors. Iodisation of salt was recognised as the method of choice. Nine years later, by April 1999, 75% of the affected countries had legislation on salt iodisation and 68% of the affected populations had access to iodised salt. The prevalence of iodine deficiency disorders decreased drastically in most countries and the deficiency disappeared completely in some such as Peru. This result constitutes a public heath success unprecedented with a non-infectious disease. However, occasional adverse effects occurred. The principle effect is iodine-induced hyperthyroidism which occurs essentially in older people with autonomous nodular goitres, especially following iodine intake that is too rapid and of too massive an increment. The incidence of the disorder is usually low and reverts spontaneously to the background rate of hyperthyroidism or even below this rate after 1 to 10 years of iodine supplementation. The possible occurrence of iodine-induced thyroiditis in susceptible individuals has not been clearly demonstrated by large epidemiological surveys. Iodine supplementation is followed by an increased prevalence of occult papillary carcinoma of the thyroid discovered at autopsy but the prognosis of thyroid cancer is improved due to a shift towards differentiated forms of thyroid cancer that are diagnosed at earlier stages. Iodine-induced hyperthyroidism and other adverse effects can be almost entirely avoided by adequate and sustained quality control and monitoring of iodine supplementation which should also confirm adequate iodine intake. Available evidence clearly confirms that the benefits of correcting iodine deficiency far outweigh the risks of iodine supplementation.
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PMID:Iodine supplementation: benefits outweigh risks. 1067 91

In this contribution, we review current knowledge on the pathogenesis, diagnosis and differential diagnosis of thyroid disorders in childhood and adolescence, as well as present an update on therapy methods and management guidelines for these disorders. This overview is conceptually divided into two parts, one focusing on thyroid functional disorders, i.e. conditions leading to hyper- and hypothyroidism, and another one pertinent to structural abnormalities of the thyroid gland, i.e. nodular disorders and thyroid cancer. Currently, congenital hypothyroidism is diagnosed in a much more timely fashion rather than in the past, rendering hypothyroidism-related mental retardation and developmental deficits very rare in newborns and children and, hence, diminishing significantly its public health impact. At the same time, considerable advances have occurred in our understanding of the molecular basis of several genetic conditions affecting the thyroid gland in childhood, such as familial non-autoimmune hyperthyroidism, as well as of the pathways leading to thyroid neoplasia.
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PMID:The spectrum of thyroid diseases in childhood and its evolution during transition to adulthood: natural history, diagnosis, differential diagnosis and management. 1171 53

Iodine deficiency is the most common cause of hypothyroidism worldwide. In persons living in iodine-replete areas, causes are congenital, spontaneous because of chronic autoimmune disease (atrophic autoimmune thyroiditis or goitrous autoimmune thyroiditis [Hashimoto's thyroiditis]), or iatrogenic because of goitrogens, drugs, or destructive treatment for thyrotoxicosis. Screening for congenital hypothyroidism exists and its use prevents mental retardation. The prevalence of spontaneous hypothyroidism is between 1% and 2% and is more common in older women and 10 times more common in women than in men. A significant proportion of subjects have asymptomatic chronic autoimmune thyroiditis and 8% of women (10% of women over 55 years of age) and 3% of men have subclinical hypothyroidism. Approximately one third of patients with newly diagnosed overt hypothyroidism have received destructive therapy for hyperthyroidism and indefinite surveillance is required. There is not much that can be done to prevent the occurrence of spontaneous autoimmune hypothyroidism, but if identified early, something can be done to prevent progression to overt disease. Controversy exists as to whether healthy adults would benefit from screening for autoimmune thyroid disease because a significant proportion of subjects tested will have evidence of mild thyroid failure. Case finding in women at menopause or visiting a primary care physician with nonspecific symptoms appears justified.
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PMID:Epidemiology and prevention of clinical and subclinical hypothyroidism. 1248 65

In Japan, mass screening tests on newborns for Cretinism have been performed since 1984, Cretinism is a very rare condition. We report the clinical course and complications of longitudinal thyroid hormone replacement therapy (liothyronine sodium: T3) of two women with Cretinism and ectopic thyroid gland for the past 33 years until 2001. They were born in April 1951 (Case 1) and in January 1952 (Case 2). On admission in June 1968, they were 17 and 16 years old. They had short stature, mental retardation, macroglossia, saddle nose, retardation of bone maturation, edematous face, coexistence of permanent teeth and deciduous teeth, abdominal distention, hypotonia, anemia, hypophosphatemia and hypercholesterolemia. After admission, Case 2 had an appendectomy for appendicitis. She was found to have a right ovarian cyst, but was not operated upon. Later, the right ovarian cyst disappeared during thyroid hormone replacement therapy. The complication in this case was NIDDM. Over secretion of thyroid hormone in for example, hyperthyroidism sometimes induces NIDDM. On their admission, a levothyroxine sodium (T4: Thyradin S) was unavailable in Japan, so we had no choice but to treat them with liothyronine sodium for thyroid hormone replacement therapy. We suspect that liothyronine sodium replacement therapy probably induced NIDDM. They experienced improved bone maturation, anemia, hypophsphatemia and hypercholesterolemia, but their intellectual and mental disabilities were not improved.
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PMID:The longitudinal course of two cases with cretinism diagnosed after adolescence. 1280 80

A lack of thyroid hormone in the postnatal period causes an irreversible mental retardation, characterized by a slowing of thoughts and movements accompanied by prolonged latencies of several evoked potentials and slowed electroencephalographic rhythms. Here we show that in cultured hippocampal and cortical neurons from postnatal rats treatment with thyroid hormone not only up-regulates Na(+)-current densities but also increases rates of rise, amplitudes and firing frequencies of action potentials. Furthermore, we show that the regulation of the Na(+)-current density by thyroid hormones also occurs in vivo: recordings from acutely isolated cortical neurons obtained from hypothyroid, euthyroid and hyperthyroid postnatal rats showed that hypothyroidism decreases the ratio of Na(+) inward- to K(+) outward-currents while hyperthyroidism upregulates Na(+)-currents with respect to K(+)-currents. Our observation of a regulation of neuronal excitability by thyroid hormone offers a direct explanation for the origin of various neurological symptoms related to thyroid dysfunction.
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PMID:Thyroid hormone regulates excitability in central neurons from postnatal rats. 1506 80

Abstract The original concept of the critical period of thyroid hormone (TH) action on brain development was proposed to identify the postnatal period during which TH supplement must be provided to a child with congenital hypothyroidism to prevent mental retardation. As neuropsychological tools have become more sensitive, it has become apparent that even mild TH insufficiency in humans can produce measurable deficits in very specific neuropsychological functions, and that the specific consequences of TH deficiency depends on the precise developmental timing of the deficiency. Models of maternal hypothyroidism, hypothyroxinaemia and congenital hyperthyroidism have provided these insights. If the TH deficiency occurs early in pregnancy, the offspring display problems in visual attention, visual processing (i.e. acuity and strabismus) and gross motor skills. If it occurs later in pregnancy, children are at additional risk of subnormal visual (i.e. contrast sensitivity) and visuospatial skills, as well as slower response speeds and fine motor deficits. Finally, if TH insufficiency occurs after birth, language and memory skills are most predominantly affected. Although the experimental literature lags behind clinical studies in providing a mechanistic explanation for each of these observations, recent studies confirm that the specific action of TH on brain development depends upon developmental timing, and studies informing us about molecular mechanisms of TH action are generating hypotheses concerning possible mechanisms to account for these pleiotropic actions.
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PMID:Timing of thyroid hormone action in the developing brain: clinical observations and experimental findings. 1550 May 40


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