scholarly journals Primary congenital hypothyroidism: defects in iodine pathways

2003 ◽  
pp. 247-256 ◽  
Author(s):  
JJ de Vijlder
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Congenital Hypothyroidism ◽  
Primary Hypothyroidism ◽  
Special Importance ◽  
Hormone Production ◽  
Central Hypothyroidism ◽  
Hormone Synthesis ◽  
Diagnosis And Classification ◽  
The Central Nervous System

The thyroid gland is the only source of thyroid hormone production. Thyroid hormone is essential for growth and development, and is of special importance for the development of the central nervous system. It was for that reason that neonatal screening on congenital hypothyroidism was introduced and is now performed in many countries. Defects in thyroid hormone production are caused by several disorders in hormone synthesis and in the development of the thyroid gland (primary hypothyroidism) or of the pituitary gland and hypothalamus (central hypothyroidism).This paper describes defects in the synthesis of thyroid hormone caused by disorders in the synthesis or iodination of thyroglobulin, leakage of iodinated proteins by a stimulated thyroid gland and the presence of abnormal iodoproteins, mainly iodinated albumin, in the thyroid gland and blood circulation. Circulating thyroglobulin and abnormal iodoproteins, as well as the breakdown products of these iodoproteins excreted in urine, are used for etiological diagnosis and classification. Moreover, our finding of an enzyme that catalyses the dehalogenation of iodotyrosines, which is important for iodine recycling and required for economical use of iodine, is also referred to.

Cognitive and Behavioral Complications of Congenital Hypothyroidism

2010 ◽  
Author(s):  
Ruth D. Nass
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Brain Development ◽  
Congenital Hypothyroidism ◽  
Behavioral Problems ◽  
Thyroid Stimulating Hormone ◽  
Primary Hypothyroidism ◽  
Normal Brain ◽  
Gene Encoding ◽  
Hormone Synthesis

Congenital hypothyroidism (CH) affects approximately 1 in 3,500 newborns. There is a female preponderance. In areas of iodine insufficiency, the incidence is higher, since iodine is a key element in the synthesis of thyroid hormone. Approximately 85% of CH cases are sporadic, whereas 15% are hereditary. Thyroid hormone is essential for normal pre- and postnatal brain development. The importance of in utero thyroid hormone status is demonstrated by the fact that maternal hypothyroidism during pregnancy is known to result in cognitive and motor deficits in the offspring (Forrest 2004; Zoeller and Rovet 2004). Congenital hypothyroidism is already expressed in fetal life; maternal T4, transferred via the placenta, is not sufficient for normal brain development (Forrest 2004; Haddow et al. 1999; Opazo et al. 2008; Pop and Vulsma 2005). Prior to newborn screening, CH that went undiagnosed and untreated for more than 3 months was associated with permanent and significant mental retardation, as well as behavioral problems. Outcome is now significantly better. Children with CH have normal intelligence, although subtle and specific cognitive and behavioral problems occur. Congenital hypothyroidism can be caused by primary hypothyroidism, due to a defect of the thyroid gland, or by central hypothyroidism secondary to defective hypothalamic or pituitary regulation of thyroid hormone. Several types of primary thyroid abnormalities may occur. Thyroid dysgenesis is the result of a missing, ectopic, or hypoplastic gland. Proteins that are crucial for normal thyroid gland development include the thyroid transcription factors PAX8, TTF1, TTF2, FOXE1 and the thyroid stimulating hormone (TSH) receptor gene. Thyroid dyshormonogenesis is generally due to an autosomal recessive genetic defect in any of many stages of thyroid hormone synthesis, secretion and transport (Moreno and Visser 2007). One in 50,000 children has autosomal dominant thyroid hormone resistance (RTH) due to a mutation in the gene encoding for the TRb thyroid receptors (Hauser et al. 1993; Weiss et al. 1993). Iodine deficiency can also cause CH (endemic cretinism) (DeLange et al. 2000). Gaudino and colleagues (2005) determined the etiology of CH in 49 non-athyroid cases.

pax2.1is required for the development of thyroid follicles in zebrafish

Development ◽  
2002 ◽  
Vol 129 (15) ◽  
pp. 3751-3760 ◽  
Author(s):  
Thomas Wendl ◽  
Klaus Lun ◽  
Marina Mione ◽  
Jack Favor ◽  
Michael Brand ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Marker Gene ◽  
Follicular Cells ◽  
Hormone Production ◽  
Zebrafish Model ◽  
Hormone Synthesis ◽  
Larval Stages ◽  
Thyroid Follicular Cells ◽  
Thyroid Development

The thyroid gland is an organ primarily composed of endoderm-derived follicular cells. Although disturbed embryonic development of the thyroid gland leads to congenital hypothyroidism in humans and mammals, the underlying principles of thyroid organogenesis are largely unknown. In this study, we introduce zebrafish as a model to investigate the molecular and genetic mechanisms that control thyroid development. Marker gene expression suggests that the molecular pathways of early thyroid development are essentially conserved between fish and mammals. However during larval stages, we find both conserved and divergent features of development compared with mammals. A major difference is that in fish, we find evidence for hormone production not only in thyroid follicular cells, but also in an anterior non-follicular group of cells.We show that pax2.1 and pax8, members of the zebrafish pax2/5/8 paralogue group, are expressed in the thyroid primordium. Whereas in mice, only Pax8 has a function during thyroid development, analysis of the zebrafish pax2.1 mutant no isthmus (noi–/–) demonstrates that pax2.1 has a role comparable with mouse Pax8 in differentiation of the thyroid follicular cells. Early steps of thyroid development are normal in noi–/–, but later expression of molecular markers is lost and the formation of follicles fails. Interestingly, the anterior non-follicular site of thyroid hormone production is not affected in noi–/–. Thus, in zebrafish, some remaining thyroid hormone synthesis takes place independent of the pathway leading to thyroid follicle formation. We suggest that the noi–/– mutant serves as a new zebrafish model for hypothyroidism.

Causes and laboratory investigation of hypothyroidism

2011 ◽  
pp. 530-537 ◽  
Author(s):  
Ferruccio Santini ◽  
Aldo Pinchera
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Thyroid Hormones ◽  
Thyroid Hormone Receptor ◽  
Hormone Secretion ◽  
Thyroid Tissue ◽  
Clinical Manifestations ◽  
Primary Hypothyroidism ◽  
Central Hypothyroidism ◽  
Resistance To Thyroid Hormones

Hypothyroidism is the clinical state that develops as a result of the lack of action of thyroid hormones on target tissues (1). Hypothyroidism is usually due to impaired hormone secretion by the thyroid, resulting in reduced concentrations of serum thyroxine (T4) and triiodothyronine (T3). The term primary hypothyroidism is applied to define the thyroid failure deriving from inherited or acquired causes that act directly on the thyroid gland by reducing the amount of functioning thyroid tissue or by inhibiting thyroid hormone production. The term central hypothyroidism is used when pituitary or hypothalamic abnormalities result in an insufficient stimulation of an otherwise normal thyroid gland. Both primary and central hypothyroidism may be transient, depending on the nature and the extent of the causal agent. Hypothyroidism following a minor loss of thyroid tissue can be recovered by compensatory hyperplasia of the residual gland. Similarly, hypothyroidism subsides when an exogenous inhibitor of thyroid function is removed. Peripheral hypothyroidism may also arise as a consequence of tissue resistance to thyroid hormones due to a mutation in the thyroid hormone receptor. Resistance to thyroid hormones is a heterogeneous clinical entity with most patients appearing to be clinically euthyroid while some of them have symptoms of thyrotoxicosis and others display selected signs of hypothyroidism. The common feature is represented by pituitary resistance to thyroid hormones, leading to increased secretion of thyrotropin that in turn stimulates thyroid growth and function. The variability in clinical manifestations depends on the severity of the hormonal resistance, the relative degree of tissue hyposensitivity, and the coexistence of associated genetic defects (see Chapter 3.4.8).

scholarly journals Red snapper fish intake improves thyroid gland activity in the hypothyroidism rat

Food Research ◽  
2021 ◽  
Vol 5 (S2) ◽  
pp. 18-24
Author(s):  
E. Herawati ◽  
R.S. Titisari ◽  
S.A.N. Husna ◽  
O.P. Astirin ◽  
T. Widiyani ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Positive Control ◽  
Negative Control ◽  
Red Snapper ◽  
Female Rats ◽  
Hormone Production ◽  
Remarkable Change ◽  
Hormone Synthesis ◽  
Thyroid Gland Activity

Congenital hypothyroidism is inadequate production of thyroid hormone in infants from birth. Treatment of hypothyroidism often involves an iodine-rich diet since iodine is a vital precursor for thyroid hormone synthesis. Red snapper fish is a saltwater fish that contain a high amount of iodine and other beneficial macro/micronutrients, yet no report was found on the effect of this fish consumption on hypothyroidism. The objective of this study was to determine the effectiveness of red snapper (Lutjanus sp.) fish on thyroid gland activity, manifested by low FT4 level and high TSH level, two diagnostic indicators of hypothyroidism. This study used a post-test and controlled group design. Pregnant female rats were given propylthiouracil orally for four weeks to induce hypothyroidism in their offspring. All hypothyroid offspring were divided into five treatment groups, i.e., negative control, positive control (thyroxin therapy), red snapper enriched diet at 25% and 50% dosage, also a combination of levothyroxine and red snapper. The thyroid gland activity was detected by measuring blood serum FT4 and TSH and histological examination of the thyroid gland using HE staining. The level of FT4 and TSH in each treatment group were analyzed with the one-way ANOVA test. The results showed that the group that received a 50% red snapper diet has a normal level of FT4 and TSH, whereas the FT4 level increased two-fold; the TSH level decreased significantly. The organization of the thyroid gland showed a remarkable change of the lumen diameter, indicating a higher amount of hormone production by the gland.

Phenotypic Variability of Patients With PAX8 Variants Presenting With Congenital Hypothyroidism and Eutopic Thyroid

2020 ◽  
Vol 106 (1) ◽  
pp. e152-e170
Author(s):  
Núria Camats ◽  
Noelia Baz-Redón ◽  
Mónica Fernández-Cancio ◽  
María Clemente ◽  
Ariadna Campos-Martorell ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Congenital Hypothyroidism ◽  
Phenotypic Variability ◽  
Hereditary Diseases ◽  
Hormone Synthesis ◽  
Functional Studies ◽  
Thyroid Hormone Synthesis ◽  
Thyroid Dyshormonogenesis

Abstract Purpose Thyroid dyshormonogenesis is a heterogeneous group of hereditary diseases produced by a total/partial blockage of the biochemical processes of thyroid-hormone synthesis and secretion. Paired box 8 (PAX8) is essential for thyroid morphogenesis and thyroid hormone synthesis. We aimed to identify PAX8 variants in patients with thyroid dyshormonogenesis and to analyze them with in vitro functional studies. Patients and Methods Nine pediatric patients with a eutopic thyroid gland were analyzed by the Catalan screening program for congenital hypothyroidism. Scintigraphies showed absent, low, or normal uptake. Only one patient had a hypoplastic gland. On reevaluation, perchlorate discharge test was negative or compatible with partial iodine-organization deficit. After evaluation, 8 patients showed permanent mild or severe hypothyroidism. Massive-sequencing techniques were used to detect variants in congenital hypothyroidism-related genes. In vitro functional studies were based on transactivating activity of mutant PAX8 on a TG-gene promoter and analyzed by a dual-luciferase assays. Results We identified 7 heterozygous PAX8 exonic variants and 1 homozygous PAX8 splicing variant in 9 patients with variable phenotypes of thyroid dyshormonogenesis. Five were novel and 5 variants showed a statistically significant impaired transcriptional activity of TG promoter: 51% to 78% vs the wild type. Conclusions Nine patients presented with PAX8 candidate variants. All presented with a eutopic thyroid gland and 7 had deleterious variants. The phenotype of affected patients varies considerably, even within the same family; but, all except the homozygous patient presented with a normal eutopic thyroid gland and thyroid dyshormonogenesis. PAX8 functional studies have shown that 6 PAX8 variants are deleterious. Our studies have proven effective in evaluating these variants.

scholarly journals AMIODARON SEBAGAI OBAT ANTI ARITMIA DAN PENGARUHNYA TERHADAP FUNGSI TIROID

2013 ◽  
Vol 3 (2) ◽  
Author(s):  
Starry H. Rampengan
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Thyroid Function ◽  
Hormone Replacement ◽  
Type I ◽  
Peripheral Tissues ◽  
Hormone Synthesis ◽  
Thyroid Hormone Metabolism ◽  
Serum T4 ◽  
Life Threatening

Abstract: Amiodarone is a highly effective anti-arrhythmic agent used in certain arrhythmias from supraventricular tachycardia to life-threatening ventricular tachycardia. Its use is associated with numerous side-effects that could deteriorate a patient’s condition. Consequently, a clinician should consider the risks and benefits of amiodarone before initiating the treatment.The thyroid gland is one of the organs affected by amiodarone. Amiodarone and its metabolite desethyl amiodaron induce alterations in thyroid hormone metabolism in the thyroid gland, peripheral tissues, and probably also in the pituitary gland. These actions result in elevations of serum T4 and rT3 concentrations, transient increases in TSH concentrations, and decreases in T3 concentrations. Both hypothyroidism and hyperthyroidism are prone to occur in patients receiving amiodarone. Amiodarone-induced hypothyroidism (AIH) results from the inability of the thyroid to escape from the Wolff-Chaikoff effect and is readily managed by either discontinuation of amiodarone or thyroid hormone replacement. Amiodarone-induced thyrotoxicosis (AIT) may arise from either iodine-induced excessive thyroid hormone synthesis (type I, usually with underlying thyroid abnormality), or destructive thyroiditis with release of preformed hormones (type II, commonly with apparently normal thyroid glands). Therefore, monitoring of thyroid function should be performed in all amiodarone-treated patients to facilitate early diagnosis and treatment of amiodarone-induced thyroid dysfunction. Key words: Amiodarone, thyroid function, side effect, management, monitoring.     Abstrak: Amiodaron adalah obat antiaritmia yang cukup efektif dalam menangani beberapa keadaaan aritmia mulai dari supraventrikuler takikardia sampai takikardia ventrikuler yang mengancam kehidupan. Namun penggunaan obat ini ternyata menimbulkan efek samping pada organ lain yang dapat menimbulkan perburukan keadaan pasien. Sehingga, dalam penggunaan amiodaron, klinisi juga harus menimbang keuntungan dan kerugian yang ditimbulkan oleh obat ini. Salah satu organ yang dipengaruhi oleh amiodaron adalah kelenjar tiroid. Amiodaron dan metabolitnya desetil amiodaron memengaruhi hormon tiroid pada kelenjar tiroid, jaringan perifer, dan mungkin pada pituitari. Aksi amiodaron ini menyebabkan peningkatan T4, rT3 dan TSH, namun menurunkan kadar T3. Hipotiroidisme dan tirotoksikosis dapat terjadi pada pasien yang diberi amiodaron. Amiodarone-induced hypothyroidism (AIH) terjadi karena ketidakmampuan tiroid melepaskan diri dari efek Wolff Chaikof, dan dapat ditangani dengan pemberian  hormon substitusi T4 atau penghentian amiodaron. Amiodarone-induced thyrotoxicosis (AIT) terjadi karena sintesis hormon tiroid yang berlebihan yang diinduksi oleh iodium (tipe I, biasanya sudah mempunyai kelainan tiroid sebelumnya) atau karena tiroiditis destruktif yang disertai pelepasan hormon tiroid yang telah terbentuk (tipe II, biasanya dengan kelenjar yang normal). Pemantauan fungsi tiroid seharusnya dilakukan pada semua pasien yang diberi amiodaron untuk memfasilitasi diagnosis dan terapi yang dini terjadinya  disfungsi tiroid yang diinduksi amiodaron. Kata Kunci: Amiodaron, fungsi tiroid, efek samping, penanganan, pemantauan.

scholarly journals Diagnosis and Management of Central Congenital Hypothyroidism

2021 ◽  
Vol 12 ◽  
Author(s):  
Peter Lauffer ◽  
Nitash Zwaveling-Soonawala ◽  
Jolanda C. Naafs ◽  
Anita Boelen ◽  
A. S. Paul van Trotsenburg
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Congenital Hypothyroidism ◽  
Neonatal Period ◽  
Neurodevelopmental Outcome ◽  
Pituitary Hormone ◽  
Feeding Problems ◽  
Severe Condition ◽  
Diagnosis And Management ◽  
Prolonged Jaundice

Central congenital hypothyroidism (CH) is defined as thyroid hormone (TH) deficiency at birth due to insufficient stimulation by the pituitary of the thyroid gland. The incidence of central CH is currently estimated at around 1:13,000. Central CH may occur in isolation, but in the majority of cases (60%) it is part of combined pituitary hormone deficiencies (CPHD). In recent years several novel genetic causes of isolated central CH have been discovered (IGSF1, TBL1X, IRS4), and up to 90% of isolated central CH cases can be genetically explained. For CPHD the etiology usually remains unknown, although pituitary stalk interruption syndrome does seem to be the most common anatomic pituitary malformation associated with CPHD. Recent studies have shown that central CH is a more severe condition than previously thought, and that early detection and treatment leads to good neurodevelopmental outcome. However, in the neonatal period the clinical diagnosis is often missed despite hospital admission because of feeding problems, hypoglycemia and prolonged jaundice. This review provides an update on the etiology and prognosis of central CH, and a practical approach to diagnosis and management of this intriguing condition.

Iodide Metabolism and Effects

2020 ◽  
pp. 25-33
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Thyroid Hormones ◽  
Dietary Supplement ◽  
Thyroid Function ◽  
Thyroid Stimulating Hormone ◽  
Hormone Synthesis ◽  
Serum Tsh ◽  
Tsh Stimulation ◽  
Sensitive Marker

Iodine (I2) is essential in the synthesis of thyroid hormones T4 and T3 and functioning of the thyroid gland. Both T3 and T4 are metabolically active, but T3 is four times more potent than T4. Our body contains 20-30 mg of I2, which is mainly stored in the thyroid gland. Iodine is naturally present in some foods, added to others, and available as a dietary supplement. Serum thyroid stimulating hormone (TSH) level is a sensitive marker of thyroid function. Serum TSH is increased in hypothyroidism as in Hashimoto's thyroiditis. In addition to regulation of thyroid function, TSH promotes thyroid growth. If thyroid hormone synthesis is chronically impaired, TSH stimulation eventually may lead to the development of a goiter. This chapter explores the iodide metabolism and effects of Hashimoto's disease.

Congenital Hypothyroidism

2017 ◽  
Author(s):  
Mary Lee Gregory
Keyword(s):  
Thyroid Hormone ◽  
Congenital Hypothyroidism ◽  
Hormone Treatment ◽  
Thyroid Stimulating Hormone ◽  
Congenital Defects ◽  
Central Hypothyroidism ◽  
Severe Intellectual Disability ◽  
Iodine Supplementation ◽  
Thyroid Hormone Biosynthesis ◽  
Hormone Biosynthesis

Congenital hypothyroidism (CH) results from the effects of insufficient thyroid hormone on the developing fetus and infant, and is characterized by severe intellectual disability and growth inhibition. CH can result from maternal iodine deficiency, which can be abolished by appropriate dietary iodine supplementation. Alternately, CH may be caused by congenital defects of the thyroid gland and thyroid hormone biosynthesis abnormalities (primary congenital hypothyroidism), or by “central hypothyroidism,” in which the brain produces insufficient thyroid stimulating hormone. Treatment of these latter etiologies requires administration of thyroid hormone.

scholarly journals Central Hypothyroidism Due to a TRHR Mutation Causing Impaired Ligand Affinity and Transactivation of Gq

2017 ◽  
Vol 102 (7) ◽  
pp. 2433-2442 ◽  
Author(s):  
Marta García ◽  
Jesús González de Buitrago ◽  
Mireia Jiménez-Rosés ◽  
Leonardo Pardo ◽  
Patricia M. Hinkle ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Molecular Mechanisms ◽  
Pituitary Hormones ◽  
Thyroid Stimulating Hormone ◽  
Consanguineous Family ◽  
Intracellular Loop ◽  
Central Hypothyroidism ◽  
Hormone Synthesis ◽  
Half Maximal Effective Concentration

Abstract Context: Central congenital hypothyroidism (CCH) is an underdiagnosed disorder characterized by deficient production and bioactivity of thyroid-stimulating hormone (TSH) leading to low thyroid hormone synthesis. Thyrotropin-releasing hormone (TRH) receptor (TRHR) defects are rare recessive disorders usually associated with incidentally identified CCH and short stature in childhood. Objectives: Clinical and genetic characterization of a consanguineous family of Roma origin with central hypothyroidism and identification of underlying molecular mechanisms. Design: All family members were phenotyped with thyroid hormone profiles, pituitary magnetic resonance imaging, TRH tests, and dynamic tests for other pituitary hormones. Candidate TRH, TRHR, TSHB, and IGSF1 genes were screened for mutations. A mutant TRHR was characterized in vitro and by molecular modeling. Results: A homozygous missense mutation in TRHR (c.392T > C; p.I131T) was identified in an 8-year-old boy with moderate hypothyroidism (TSH: 2.61 mIU/L, Normal: 0.27 to 4.2; free thyroxine: 9.52 pmol/L, Normal: 10.9 to 25.7) who was overweight (body mass index: 20.4 kg/m2, p91) but had normal stature (122 cm; –0.58 standard deviation). His mother, two brothers, and grandmother were heterozygous for the mutation with isolated hyperthyrotropinemia (TSH: 4.3 to 8 mIU/L). The I131T mutation, in TRHR intracellular loop 2, decreases TRH affinity and increases the half-maximal effective concentration for signaling. Modeling of TRHR-Gq complexes predicts that the mutation disrupts the interaction between receptor and a hydrophobic pocket formed by Gq. Conclusions: A unique missense TRHR defect identified in a consanguineous family is associated with central hypothyroidism in homozygotes and hyperthyrotropinemia in heterozygotes, suggesting compensatory elevation of TSH with reduced biopotency. The I131T mutation decreases TRH binding and TRHR-Gq coupling and signaling.

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