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.

H9c2 cardiomyoblasts produce thyroid hormone

2008 ◽  
Vol 294 (5) ◽  
pp. C1227-C1233 ◽  
Author(s):  
Christof Meischl ◽  
Henk P. Buermans ◽  
Thierry Hazes ◽  
Marian J. Zuidwijk ◽  
René J. P. Musters ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Gland ◽  
Thyroid Stimulating Hormone ◽  
Thyroid Peroxidase ◽  
Sodium Iodide Symporter ◽  
Hormone Synthesis ◽  
Cardiovascular Hemodynamics ◽  
Wide Range ◽  
Vitro Model

Thyroid hormone acts on a wide range of tissues. In the cardiovascular system, thyroid hormone is an important regulator of cardiac function and cardiovascular hemodynamics. Although some early reports in the literature suggested an unknown extrathyroidal source of thyroid hormone, it is currently thought to be produced exclusively in the thyroid gland, a highly specialized organ with the sole function of generating, storing, and secreting thyroid hormone. Whereas most of the proteins necessary for thyroid hormone synthesis are thought to be expressed exclusively in the thyroid gland, we now have found evidence that all of these proteins, i.e., thyroglobulin, DUOX1, DUOX2, the sodium-iodide symporter, pendrin, thyroid peroxidase, and thyroid-stimulating hormone receptor, are also expressed in cardiomyocytes. Furthermore, we found thyroglobulin to be transiently upregulated in an in vitro model of ischemia. When performing these experiments in the presence of 125I, we found that 125I was integrated into thyroglobulin and that under ischemia-like conditions the radioactive signal in thyroglobulin was reduced. Concomitantly we observed an increase of intracellularly produced, 125I-labeled thyroid hormone. In conclusion, our findings demonstrate for the first time that cardiomyocytes produce thyroid hormone in a manner adapted to the cell's environment.

scholarly journals Desethylamiodarone antagonizes the effect of thyroid hormone at the molecular level

2001 ◽  
pp. 59-64 ◽  
Author(s):  
F Bogazzi ◽  
L Bartalena ◽  
S Brogioni ◽  
A Burelli ◽  
F Raggi ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Molecular Mechanisms ◽  
Thyroid Hormone Receptor ◽  
Molecular Level ◽  
Inhibitory Effect ◽  
Mobility Shift ◽  
Down Regulation ◽  
Nih3t3 Cells ◽  
Peripheral Tissues

OBJECTIVE: To evaluate the molecular mechanisms of the inhibitory effects of amiodarone and its active metabolite, desethylamiodarone (DEA) on thyroid hormone action. MATERIALS AND METHODS: The reporter construct ME-TRE-TK-CAT or TSHbeta-TRE-TK-CAT, containing the nucleotide sequence of the thyroid hormone response element (TRE) of either malic enzyme (ME) or TSHbeta genes, thymidine kinase (TK) and chloramphenicol acetyltransferase (CAT) was transiently transfected with RSV-TRbeta into NIH3T3 cells. Gel mobility shift assay (EMSA) was performed using labelled synthetic oligonucleotides containing the ME-TRE and in vitro translated thyroid hormone receptor (TR)beta. RESULTS: Addition of 1 micromol/l T4 or T3 to the culture medium increased the basal level of ME-TRE-TK-CAT by 4.5- and 12.5-fold respectively. Amiodarone or DEA (1 micromol/l) increased CAT activity by 1.4- and 3.4-fold respectively. Combination of DEA with T4 or T3 increased CAT activity by 9.4- and 18.9-fold respectively. These data suggested that DEA, but not amiodarone, had a synergistic effect with thyroid hormone on ME-TRE, rather than the postulated inhibitory action; we supposed that this was due to overexpression of the transfected TR into the cells. When the amount of RSV-TRbeta was reduced until it was present in a limited amount, allowing competition between thyroid hormone and the drug, addition of 1 micromol/l DEA decreased the T3-dependent expression of the reporter gene by 50%. The inhibitory effect of DEA was partially due to a reduced binding of TR to ME-TRE, as assessed by EMSA. DEA activated the TR-dependent down-regulation by the negative TSH-TRE, although at low level (35% of the down-regulation produced by T3), whereas amiodarone was ineffective. Addition of 1 micromol/l DEA to T3-containing medium reduced the T3-TR-mediated down-regulation of TSH-TRE to 55%. CONCLUSIONS: Our results demonstrate that DEA, but not amiodarone, exerts a direct, although weak, effect on genes that are regulated by thyroid hormone. High concentrations of DEA antagonize the action of T3 at the molecular level, interacting with TR and reducing its binding to TREs. This effect may contribute to the hypothyroid-like effect observed in peripheral tissues of patients receiving amiodarone treatment.

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 Acrylamide does not induce tumorigenesis or major defects in mice in vivo

2008 ◽  
Vol 198 (2) ◽  
pp. 301-307 ◽  
Author(s):  
Ling Jin ◽  
Vanessa Chico-Galdo ◽  
Claude Massart ◽  
Christine Gervy ◽  
Viviane De Maertelaere ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Chronic Administration ◽  
Serum Levels ◽  
Human Thyroid ◽  
Thyroid Cell ◽  
Thyroid Cells ◽  
Hormone Synthesis ◽  
Rat Thyroid

Chronic administration of acrylamide has been shown to induce thyroid tumors in rat. In vitro acrylamide also causes DNA damage, as demonstrated by the comet assay, in various types of cells including human thyroid cells and lymphocytes, as well as rat thyroid cell lines. In this work, mice were administered acrylamide in their drinking water in doses comparable with those used in rats, i.e., around 3–4 mg/kg per day for mice treated 2, 6, and 8 months. Some of the mice were also treated with thyroxine (T4) to depress the activity of the thyroid. Others were treated with methimazole that inhibits thyroid hormone synthesis and consequently secretion and thus induces TSH secretion and thyroid activation. These moderate treatments were shown to have their known effect on the thyroid (e.g. thyroid hormone and thyrotropin serum levels, thyroid gland morphology…). Besides, T4 induced an important polydipsia and degenerative hypertrophy of adrenal medulla. Acrylamide exerted various discrete effects and at high doses caused peripheral neuropathy, as demonstrated by hind-leg paralysis. However, it did not induce thyroid tumorigenesis. These results show that the thyroid tumorigenic effects of acrylamide are not observed in another rodent species, the mouse, and suggest the necessity of an epidemiological study in human to conclude on a public health policy.

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.

Screening for New Markers to Assess Thyroid Hormone Action by OMICs Analysis of Human Samples

2020 ◽  
Vol 128 (06/07) ◽  
pp. 479-487 ◽  
Author(s):  
Nele Friedrich ◽  
Maik Pietzner ◽  
Beatrice Engelmann ◽  
Georg Homuth ◽  
Dagmar Führer ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Function ◽  
Clinical Symptoms ◽  
Pituitary Tumors ◽  
Population Based ◽  
Thyroid Stimulating Hormone ◽  
Central Hypothyroidism ◽  
Free Thyroid Hormones ◽  
Molecular Alterations ◽  
Novel Biomarkers

ABSTRACTDetermination of the levels of thyroid-stimulating hormone (TSH) and free thyroid hormones (fTHs) is crucial for assessing thyroid function. However, as a result of inter-individual genetic variability and different environmental factors individual set points exist for TSH and fTHs and display considerable variation. Furthermore, under specific pathophysiological conditions like central hypothyroidism, TSH secreting pituitary tumors, or thyroid hormone resistance the established markers TSH and fTH fail to reliably predict thyroid function and adequate supply of TH to peripheral organs. Even in case of overt hyper- and hypothyroidism circulating fTH concentrations do not correlate with clinical symptoms. Therefore, there is a clear need for novel, more specific biomarkers to diagnose and monitor thyroid function. OMICs screening approaches allow parallel profiling of hundreds to thousands of molecules and thus comprehensive monitoring of molecular alterations in tissues and body fluids that might be associated with changes in thyroid function. These techniques thus constitute promising tools for the identification of urgently needed novel biomarkers. This mini review summarizes the findings of OMICs studies in thyroid research with a particular focus on population-based and patient studies as well as interventional approaches investigating the effects of thyroid hormone administration.

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.

STUDIES OF THYROID HORMONE SYNTHESIS IN EXPERIMENTAL AUTOIMMUNE THYROIDITIS

1962 ◽  
Vol 40 (2) ◽  
pp. 297-306 ◽  
Author(s):  
W. Hung ◽  
R. W. Chandler ◽  
M. A. Kyle ◽  
R. M. Blizzard
Keyword(s):  
Thyroid Hormone ◽  
Accumulation Rate ◽  
Potassium Thiocyanate ◽  
Thyroid Stimulating Hormone ◽  
Accumulation Rates ◽  
Experimental Autoimmune Thyroiditis ◽  
Thyroid Cells ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis ◽  
Thyroid Glands

ABSTRACT Thyroid hormone synthesis in rabbits with experimentally induced thyroiditis is compared with hormone synthesis in normal rabbits and in immunized rabbits receiving thyroid stimulating hormone. The immunized rabbits showed decreased thyroidal accumulation rates for 131I. T. S. H. administration produced an increase in the accumulation rate of immunized animals, but this increase was smaller than that obtained in normal rabbits stimulated with T. S. H. None of the rabbits' thyroids discharged iodide with the administration of potassium thiocyanate. Twenty-four and 48 hours after 131I was administered, chromatography was performed on digested extracts of the thyroid glands. In the digested extracts of thyroids removed from normal rabbits the mono:diiodotyrosine ratio was greater than 1.0 whereas the extracts of thyroids removed from immunized rabbits and normal rabbits stimulated with T. S. H. consistently had a ratio of less than 1.0. Thyroxine was not always present in the thyroids of normal rabbits but was consistently found in the thyroids of the immunized and T. S. H. treated animals. These findings suggest that the remaining thyroid cells in the glands of immunized rabbits are operating under increased T. S. H. stimulation. The experimental thyroiditis of immunized rabbits was similar to Hashimoto's thyroiditis in respect to histological alteration and the presence of anti-thyroid antibodies. 131I accumulation rates, response to potassium thiocyanate, and chromatography studies revealed no correlation between the two groups.

Effects of a selenium deficient diet on thyroid function of normal and perchlorate treated rats

1988 ◽  
Vol 118 (4) ◽  
pp. 495-502 ◽  
Author(s):  
J. Golstein ◽  
B. Corvilain ◽  
F. Lamy ◽  
D. Paquer ◽  
J. E. Dumont
Keyword(s):  
Thyroid Hormone ◽  
Tap Water ◽  
Selenium Deficiency ◽  
Thyroid Peroxidase ◽  
Deficient Diet ◽  
Adult Rats ◽  
Pregnant Rats ◽  
Hormone Synthesis ◽  
Thyroid Hormone Synthesis

Abstract. Pregnant rats were submitted to a selenium-deficient diet immediately after mating; it was continued for 4 weeks after delivery. The pups were sacrificed at 3 and 4 weeks of age. Perchlorate, an antithyroid agent inhibiting iodide trapping in the thyroid, was administered via the drinking water to half of the rats. Rats submitted to a normal laboratory diet and to the experimental diet supplemented with selenium were used as controls. The effects of selenium deficiency were an increase in the number of growth abnormalities, growth retardation, and decreased seleno-dependent glutathione peroxidase (GSH-Px) activity in plasma and in various organs. These effects were relieved by selenium supplementation in the diet. Perchlorate treatment induced the classic picture of primary hypothyroidism. Selenium deficiency increased thyroid hormone levels in perchlorate-treated rats and in controls drinking tap water. In the latter group, it also decreased TSH plasma concentration and thyroid weight. These effects were partially reversed by Se supplementation. In vitro experiments, performed on adult rats, revealed increased radioiodide uptake and organification in glands from the rats submitted to the selenium-free diet. Plasma T3 half-life was similar in control and Se-deficient rats. These data suggest a higher efficiency of thyroid hormone synthesis in the thyroids of selenium-deficient rats, despite a lower thyroid stimulation as evaluated by serum TSH. They are compatible with the hypothesis that decreased selenium supply, leading to a decreased GSH-Px in the thyroid, increases hydrogen peroxide steady state level and thus thyroid peroxidase activity and thyroid hormone synthesis.

scholarly journals Molecular regulation of follicle-stimulating hormone synthesis, secretion and action

2018 ◽  
Vol 60 (3) ◽  
pp. R131-R155 ◽  
Author(s):  
Nandana Das ◽  
T Rajendra Kumar
Keyword(s):  
Molecular Mechanisms ◽  
Follicle Stimulating Hormone ◽  
Thyroid Stimulating Hormone ◽  
Α Subunit ◽  
Physiological Regulation ◽  
Hormone Synthesis ◽  
The Common ◽  
Blocking Antibodies ◽  
Recombinant Human Fsh ◽  
Stimulating Hormone

Follicle-stimulating hormone (FSH) plays fundamental roles in male and female fertility. FSH is a heterodimeric glycoprotein expressed by gonadotrophs in the anterior pituitary. The hormone-specific FSHβ-subunit is non-covalently associated with the common α-subunit that is also present in the luteinizing hormone (LH), another gonadotrophic hormone secreted by gonadotrophs and thyroid-stimulating hormone (TSH) secreted by thyrotrophs. Several decades of research led to the purification, structural characterization and physiological regulation of FSH in a variety of species including humans. With the advent of molecular tools, availability of immortalized gonadotroph cell lines and genetically modified mouse models, our knowledge on molecular mechanisms of FSH regulation has tremendously expanded. Several key players that regulate FSH synthesis, sorting, secretion and action in gonads and extragonadal tissues have been identified in a physiological setting. Novel post-transcriptional and post-translational regulatory mechanisms have also been identified that provide additional layers of regulation mediating FSH homeostasis. Recombinant human FSH analogs hold promise for a variety of clinical applications, whereas blocking antibodies against FSH may prove efficacious for preventing age-dependent bone loss and adiposity. It is anticipated that several exciting new discoveries uncovering all aspects of FSH biology will soon be forthcoming.

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