Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
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.
 ...
PMID:Timing of thyroid hormone action in the developing brain: clinical observations and experimental findings. 1550 May 40

Johanson-Blizzard syndrome is an extremely rare ectodermal dysplastic disorder characterized by aplasia or hypoplasia of alae nasi, midline scalp defects, growth retardation, varying degrees of mental retardation, hypothyroidism, exocrine pancreatic insufficiency and congenital deafness. This condition is supposed to be an autosomal recessive disorder. We are reporting a female neonate with the characteristic features and an uncommon less emphasized feature viz. cafe-au-lait spots.
 ...
PMID:Johanson--blizzard syndrome. 1563 Mar 23

Deletion of a segment of the long arm of chromosome 18 causes characteristic physical features and mental retardation. Autoimmune disorders have been described with this syndrome in a limited number of reports. We describe 2 cases of autoimmune hypothyroidism in children with 18q deletion syndrome.
 ...
PMID:Autoimmune thyroiditis in 18q deletion syndrome. 1622 44

The prognosis of patients with acute lymphoblastic leukemia (ALL) and central nervous system (CNS) relapse has historically been very poor. Although chemo-radiotherapy has improved outcomes, some patients still have a poor prognosis after CNS relapse. Therefore, allogeneic hematopoietic stem cell transplantation (allo-SCT) has recently become an option for treatment of CNS leukemia; however, information, particularly on the long-term outcome of transplant recipients, is limited. We performed allo-SCT in eight pediatric patients with ALL (n=7) or T-cell type non-Hodgkin's lymphoma (n=1), who had isolated CNS relapse. All patients survived for a median of 70.5 (range, 13-153) months after SCT. Sequelae developed late in some patients: mental retardation (IQ=47) in one patient, severe alopecia in two patients, limited chronic graft-versus-host-disease in three patients, and amenorrhea and/or hypothyroidism in three patients. Except for a pre-school child with post transplant CNS relapse, six out of seven patients show normal school/social performance. Our results clearly indicate a high cure rate of isolated CNS relapse by allo-SCT in pediatric lymphoid malignancies; however, there needs to be further studies to determine which are the appropriate candidates for transplantation and what is the best transplant regimen to achieve high cure rate and maintain good quality of life.
 ...
PMID:Allogeneic stem cell transplantation in children with acute lymphoblastic leukemia after isolated central nervous system relapse: our experiences and review of the literature. 1624 16

Albright hereditary osteodystrophy (AHO) is characterized by a symptom complex including short stature, brachymetacarpia, obesity, round facies, cutaneous osteomas, and mental retardation. AHO is caused by mutations in the GNAS-gene localized on chromosome 20 encoding for Gsalpha protein, a signal transducer of endocrine pathways. Therefore, AHO is often associated with endocrinopathy such as pseudohypoparathyroidism or hypothyroidism. A nine-month-old boy presented with typical features of this syndrome. The diagnosis was confirmed by biochemical and molecular analyses. An unusual feature was calcinosis cutis at such an early age, which led to extensive differential diagnostic procedures.
 ...
PMID:[Calcinosis cutis in Albright hereditary osteodystrophy: pseudohypoparathyroidism type Ia]. 1627 Feb 3

The mechanism by which a lack of thyroid hormone in the early development of the brain causes permanent mental retardation in cretins is currently unknown. On the other hand, an abnormality in dopamine-related brain function is believed to underlie some forms of mental illness. In this study, we demonstrate that although the activation of a dopaminergic D(2)-like receptor inhibited glutamatergic transmission in the hippocampal slices of normal adult rats, indicating the inhibitory action of the D(2)-like receptor on glutamatergic transmission, it markedly enhanced glutamatergic transmission both in a mutant hypothyroid rat with a missense mutation in thyroglobulin and in hypothyroid rats treated with methylmercaptoimidazole (MMI), indicating the excitatory action of the D(2)-like receptor on glutamatergic transmission. Paired pulse facilitation of field excitatory postsynaptic potentials was reduced by the activation of the D(2)-like receptors from MMI-induced hypothyroid rats, suggesting a presynaptic locus of the excitatory action of the D(2)-like receptors. In normal rats, the excitatory D(2)-like dopamine receptors were observed in the developing stages and were completely replaced by normal inhibitory responses up to adulthood. Furthermore, the continuous supplement of thyroxine from birth exerted a normalising effect on the abnormal excitatory property of D(2)-like dopamine receptors in the hippocampal slices of MMI-treated hypothyroid rats. From these results, it is suggested that thyroxine may play a crucial role in reversing the excitatory property of D(2)-like dopaminergic receptors in the immature brain to an inhibitory one in the mature brain. Moreover, we suggest that the abnormal excitatory property of D(2)-like dopaminergic receptors may develop in response to a lack of thyroxine and may contribute to some central nervous system deficits, including cognitive dysfunctions accompanied by hypothyroidism.
 ...
PMID:Dopamine D(2)-like receptor function is converted from excitatory to inhibitory by thyroxine in the developmental hippocampus. 1628 31

We present a case of 12-year-old boy with idiopathic benign bilateral testicular enlargement. We eliminated precocious puberty, juvenile hypothyroidism, adrenal rest tumors, X-linked mental retardation, and bilateral testicular neoplasms. The clinical and laboratory features and differential diagnosis of benign bilateral testicular enlargement are discussed.
 ...
PMID:Idiopathic benign bilateral testicular enlargement in a pubertal boy: a case report and review of literature. 1629 Nov 35

Primary congenital hypothyroidism is a common preventable cause of mental retardation. Neonatal thyroid screening is highly successful in early diagnosis and the improvement of developmental prognosis in the hypothyroid neonate. However, rarely cases could be missed, so doctors must be aware of the earl symptoms and signs of hypothyroidism. Therefore, the purpose of this study was to emphasize the presenting clinical features of primary congenital hypothyroidism at the age of diagnosis. The study population included 17 children with primary congenital hypothyroidism who attended the Department of Pediatrics, University Clinical Center Tuzla between 1986 and 1999. The diagnosis of all patients was confirmed by serum thyroid function tests (T4 and TSH). Of the 17 patients 10 (58.8%) were diagnosed in the first three months of life and 3 of them (17.6%) between fourth and sixth month of life. Four children (23.5%) were diagnosed after the age of six months. In the first three months of life hypothermia, constipation, jaundice, poor feeding, hoarse cry, macroglossia and hypoactivity were the moste common symptoms. Among the 17 patients with primary congenital hypothyroidism 5 of them (29.4 %) were diagnosed to have disgenetic thyroid tissue and 12 (70.6%) as having dyshormonogenesis. TSH and T4 levels were higher in patients in whom thyroid tissue was dysgenetic as comapared with those with dyshormonogenesis but the difference was not statistically significant (p > 0.05). Now it is expected that neonatal screening program in Bosnia and Herzegovina Federation will contribute to the detection of primary congenital hypothyroidism in early days of life. However, until an effective screening test is not yet routine in whole country, paediatricians should consider the diagnosis of hypothyroidism whenever it is clinically suggested.
 ...
PMID:Clinical presentation of primary congenital hypothyroidism: experience before mass screening. 1635 94

Dyshormonogenesis is an uncommon cause of congenital hypothyroidism. The most common abnormality is absent or insufficient thyroid peroxidase enzyme. Perchlorate discharge test can be used to diagnose thyroid peroxidase deficiency. We report three siblings with hypothyroidism due to thyroid dyshormonogenesis. Early institution of therapy in these patients can prevent mental retardation and other features of hypothyroidism.
 ...
PMID:Thyroid dyshormonogenesis. 1642 61


<< Previous 1 2 3 4 5 6 7 8 9 10