scholarly journals Extrathyroidal thyroid hormone synthesis?

2011 ◽  
Vol 210 (1) ◽  
pp. 3-4 ◽  
Author(s):  
Marian Ludgate
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Thyroid Hormones ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis

A paper published in this issue of the Journal of Endocrinology has revisited the hypothesis that thyroid hormones may be generated by tissues outside the thyroid gland in higher organisms including mammals. This commentary appraises the strengths and weaknesses of the study, the alternative explanations for the findings and possible future measures to investigate further. The concept of extrathyroidal thyroxine and triiodothyronine synthesis has previously been proposed; by assuming that Nagao et al. and earlier authors are correct, the plausibility and possible mechanisms underlying the hypothesis are discussed.

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.

scholarly journals Endogenous thyroid hormones modulate pituitary somatotroph differentiation during chicken embryonic development

2004 ◽  
Vol 180 (1) ◽  
pp. 45-53 ◽  
Author(s):  
L Liu ◽  
TE Porter
Keyword(s):  
Thyroid Hormone ◽  
Embryonic Development ◽  
Thyroid Hormones ◽  
Synthesis Inhibitor ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis ◽  
Growth Hormone Cell ◽  
Thyroid Hormone Levels

Growth hormone cell differentiation normally occurs between day 14 and day 16 of chicken embryonic development. We reported previously that corticosterone (CORT) could induce somatotroph differentiation in vitro and in vivo and that thyroid hormones could act in combination with CORT to further augment the abundance of somatotrophs in vitro. The objective of the present study was to test our hypothesis that endogenous thyroid hormones regulate the abundance of somatotrophs during chicken embryonic development. Plasma samples were collected on embryonic day (e) 9-14. We found that plasma CORT and thyroid hormone levels increased progressively in mid-embryogenesis to e 13 or e 14, immediately before normal somatotroph differentiation. Administration of thyroxine (T4) and triiodothyronine (T3) into the albumen of fertile eggs on e 11 increased somatotroph proportions prematurely on e 13 in the developing chick embryos in vivo. Furthermore, administration of methimazole, the thyroid hormone synthesis inhibitor, on e 9 inhibited somatotroph differentiation in vivo, as assessed on e 14; this suppression was completely reversed by T3 replacement on e 11. Since we reported that T3 alone was ineffective in vitro, we interpret these findings to indicate that the effects of treatments in vivo were due to interactions with endogenous glucocorticoids. These results indicate that treatment with exogenous thyroid hormones can modulate somatotroph abundance and that endogenous thyroid hormone synthesis likely contributes to normal somatotroph differentiation.

scholarly journals Production of Immunoreactive Thyroglobulin C-Terminal Fragments during Thyroid Hormone Synthesis

Endocrinology ◽  
2000 ◽  
Vol 141 (7) ◽  
pp. 2518-2525 ◽  
Author(s):  
Christine Duthoit ◽  
Valérie Estienne ◽  
Frédéric Delom ◽  
Josée-Martine Durand-Gorde ◽  
Bernard Mallet ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Monoclonal Antibodies ◽  
Free Radicals ◽  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Fenton Reaction ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis ◽  
Generating System ◽  
Mediated Oxidation

Here, we studied the fragmentation of the prothyroid hormone, thyroglobulin (Tg), which occurs during thyroid hormone synthesis, a process which involves iodide, thyroperoxidase, and the H2O2-generating system, consisting of glucose and glucose oxidase. Various peptides were found to be immunoreactive to autoantibodies to Tg from patients and monoclonal antibodies directed against the immunodominant region of Tg. The smallest peptide (40 kDa) bore thyroid hormones and was identified at the C-terminal end of the Tg molecule, which shows homologies with acetylcholinesterase. Similar peptides were obtained by performing metal-mediated oxidation of Tg via a Fenton reaction. It was concluded that the oxidative stress induced during hormone synthesis generates free radicals, which, in turn, cleave Tg into immunoreactive peptides.

Research Paper Effects of 13-HPODE on Expression of Genes Involved in Thyroid Hormone Synthesis, Iodide Uptake and Formation of Hydrogen Peroxide in Porcine Thyrocytes

2006 ◽  
Vol 76 (6) ◽  
pp. 398-406 ◽  
Author(s):  
Luci ◽  
Bettzieche ◽  
Eder
Keyword(s):  
Hydrogen Peroxide ◽  
Linoleic Acid ◽  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Thyroid Peroxidase ◽  
Iodide Uptake ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis ◽  
Expression Of Genes ◽  
Production Of Hydrogen

It has been shown that dietary oxidized fats influence thyroid function in rats and pigs. Mechanisms underlying this phenomenon are unknown. This study was performed to investigate whether 13-hydroperoxy-9,11-octadecadienic acid (13-HPODE), a primary oxidation product of linoleic acid, affects expression of genes involved in thyroid hormone synthesis and formation of hydrogen peroxide in primary porcine thyrocytes. Thyrocytes were treated with 13-HPODE in concentrations between 20 and 100 μM. Cells treated with vehicle alone ("control cells") or with equivalent concentrations of linoleic acid were considered as controls. Treatment of cells with 13-HPODE did not affect cell viability but increased the activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase (p < 0.05) compared to control cells or cells treated with linoleic acid. Relative mRNA concentrations of genes involved in thyroid hormone synthesis like sodium iodide symporter, thyrotropin receptor, and thyroid peroxidase, as well as iodide uptake, did not differ between cells treated with 13-HPODE and control cells or cells treated with linoleic acid. Treatment of cells with 13-HPODE, however, reduced the relative mRNA concentrations of dual oxidase-2 and the formation of hydrogen peroxide compared to control cells or cells treated with linoleic acid (p < 0.05). Because the production of hydrogen peroxide is rate-limiting for the synthesis of thyroid hormones, it is suggested that 13-HPODE could have an impact on the formation of thyroid hormones in the thyroid 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 Bioinorganic Chemistry in Thyroid Gland: Effect of Antithyroid Drugs on Peroxidase-Catalyzed Oxidation and Iodination Reactions

2006 ◽  
Vol 2006 ◽  
pp. 1-9 ◽  
Author(s):  
Gouriprasanna Roy ◽  
G. Mugesh
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Bioinorganic Chemistry ◽  
Antithyroid Drugs ◽  
Thyroid Peroxidase ◽  
Current Interest ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis ◽  
Interesting Compound ◽  
Catalyzed Oxidation

Propylthiouracil (PTU) and methimazole (MMI) are the most commonly used antithyroid drugs. The available data suggest that these drugs may block the thyroid hormone synthesis by inhibiting the thyroid peroxidase (TPO) or diverting oxidized iodides away from thyroglobulin. It is also known that PTU inhibits the selenocysteine-containing enzyme ID-1 by reacting with the selenenyl iodide intermediate (E-SeI). In view of the current interest in antithyroid drugs, we have recently carried out biomimetic studies to understand the mechanism by which the antithyroid drugs inhibit the thyroid hormone synthesis and found that the replacement of sulfur with selenium in MMI leads to an interesting compound that may reversibly block the thyroid hormone synthesis. Our recent results on the inhibition of lactoperoxidase (LPO)-catalyzed oxidation and iodination reactions by antithyroid drugs are described.

THE INFLUENCE OF THE PLASMA INORGANIC IODINE CONCENTRATION ON THYROID FUNCTION IN DEHALOGENASE DEFICIENCY

1967 ◽  
Vol 55 (2) ◽  
pp. 361-368 ◽  
Author(s):  
R. McG. Harden ◽  
W. D. Alexander ◽  
S. Papadopoulos ◽  
M. T. Harrison ◽  
S. Macfarlane
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Function ◽  
Iodine Concentration ◽  
Rapid Rise ◽  
Normal Range ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis ◽  
Iodine Metabolism ◽  
Inorganic Iodine ◽  
Circulating Levels

ABSTRACT Iodine metabolism and thyroid function were studied in a patient with hypothyroidism and goitre due to dehalogenase deficiency. Initially the plasma inorganic iodine (PII) level was within the normal range but circulating levels of hormone were low and the thyroid clearance and absolute uptake of iodine (AIU) by the thyroid were high. Administration of iodide supplements resulted in a rapid rise in the plasma thyroxine concentration and restoration of the euthyroid state. Thyroid hormone synthesis appeared to proceed normally when the PII exceeded 1.0 μg/100 ml. This was achieved by increasing the intake of iodide by 612 μg per day. At PII levels around 10 μg/100 ml there was evidence of increased levels of circulating thyroid hormone.

Thyroid hormone synthesis during hypothermia in rats

1963 ◽  
Vol 19 (2) ◽  
pp. 103-104 ◽  
Author(s):  
Vera Dolgova ◽  
N. Serafimow ◽  
G. Sestakov
Keyword(s):  
Thyroid Hormone ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis
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