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Kihara M, Amino N, Hirokawa M, Matsuzuka F, Miyauchi A. Unusual finding on ultrasonography of follicular thyroid carcinoma including poorly differentiated thyroid carcinoma. Thyroid 2008; 18:1021-2. [PMID: 18788925 DOI: 10.1089/thy.2008.0060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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102
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Lizcano F, Salvador J. EFFECTS OF DIFFERENT TREATMENTS FOR HYPERTHYROIDISM ON THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS. Clin Exp Pharmacol Physiol 2008; 35:1085-90. [PMID: 18505442 DOI: 10.1111/j.1440-1681.2008.04966.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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103
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Bansal R, Zoeller RT. Polychlorinated biphenyls (Aroclor 1254) do not uniformly produce agonist actions on thyroid hormone responses in the developing rat brain. Endocrinology 2008; 149:4001-8. [PMID: 18420739 PMCID: PMC2488245 DOI: 10.1210/en.2007-1774] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone (TH) is essential for normal brain development, and polychlorinated biphenyls (PCBs) are known to interfere with TH action in the developing brain. Thus, it is possible that the observed neurotoxic effects of PCB exposure in experimental animals and humans are mediated in part by their ability to interfere with TH signaling. PCBs may interfere with TH signaling by reducing circulating levels of TH, acting as TH receptor analogs, or both. If PCBs act primarily by reducing serum TH levels, then their effects should mimic those of low TH. In contrast, if PCBs act primarily as TH agonists in the developing brain, then they should mimic the effect of T(4) in hypothyroid animals. We used a two-factor design to test these predictions. Both hypothyroidism (Htx) and/or PCB treatment reduced serum free and total T(4) on postnatal d 15. However, only Htx increased pituitary TSHbeta expression. RC3/neurogranin expression was decreased by Htx and increased by PCB treatment. In contrast, Purkinje cell protein-2 expression was reduced in hypothyroid animals and restored by PCB treatment. Finally, PCB treatment partially ameliorated the effect of Htx on the thickness of the external granule layer of the cerebellum. These studies demonstrate clearly that PCB exposure does not mimic the effect of low TH on several important TH-sensitive measures in the developing brain. However, neither did PCBs mimic T(4) in hypothyroid animals on all end points measured. Thus, PCBs exert a complex action on TH signaling in the developing brain.
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Panda S, Kar A. Evaluation of the antithyroid, antioxidative and antihyperglycemic activity of scopoletin from Aegle marmelos leaves in hyperthyroid rats. Phytother Res 2008; 20:1103-5. [PMID: 17078113 DOI: 10.1002/ptr.2014] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Scopoletin (7-hydroxy-6-methoxy coumarin) was isolated from the leaves of Aegle marmelos and evaluated for its potential to regulate hyperthyroidism, lipid peroxidation and hyperglycemia in levo-thyroxine-induced hyperthyroid rats. Scopoletin (1.00 mg/kg, p.o.) administered daily for 7 days to levo-thyroxine-treated animals decreased the levels of serum thyroid hormones and glucose as well as hepatic glucose-6-phosphatase activity, demonstrating its potential to regulate hyperthyroidism and hyperglycemia. Scopoletin also inhibited hepatic lipid peroxidation and increased the activity of antioxidants, superoxide dismutase and catalase. Compared with the standard antithyroid drug, propylthiouracil, scopoletin exhibited a superior therapeutic activity, since unlike propylthiouracil, it also inhibited hepatic lipid peroxidation. These findings indicate that scopoletin has the potential to inhibit thyroid function and hyperglycemia without hepatotoxicity.
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Rathi MS, Miles JN, Jennings PE. Weight gain during the treatment of thyrotoxicosis using conventional thyrostatic treatment. J Endocrinol Invest 2008; 31:505-8. [PMID: 18591881 DOI: 10.1007/bf03346398] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVE Patients often lose considerable weight prior to the diagnosis of thyrotoxicosis. Regaining weight with treatment of thyrotoxicosis until hormone levels normalise is expected. This study was aimed to determine whether patients continued to put on weight once they were euthyroid. STUDY DESIGN AND METHOD The records of 60 consecutive euthyroid patients were studied. All patients were rendered euthyroid on thyrostatic medication alone. Patients on a block and replacement regime, those who developed transient hypothyroidism on treatment or other diagnoses causing weight gain were excluded. RESULTS The mean age of study group was 46.13 yr (21-73). Male:female ratio was 5:55. 36 (60%) patients had diagnosis of Graves' disease. On initial presentation weight was 67.75 kg (SEM 2.1) with body mass index (BMI) of 25.8. Patients took 6.7 months (mean) to become euthyroid. Mean weight when euthyroid was 71.61 kg (range 46-125). Even after becoming euthyroid, patient continued to gain weight at 3, 6, and 9 months and mean weight gain was 2.04 kg (SD 18.14) at 3 months (p=0.003). This weight gain was not related to patients' age, gender, BMI, duration or dose of treatment required to achieve euthyroidism. Diagnosis of Graves' disease and non-smoking status independently predicted weight gain. CONCLUSION We have demonstrated that patients with thyrotoxicosis continue to gain weight for at least 6 months even after becoming euthyroid. Patients with Graves' disease were more likely to gain weight compared to others. Smokers gained least weight. Preventing this weight gain warrants further investigation.
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Gereben B, Zeöld A, Dentice M, Salvatore D, Bianco AC. Activation and inactivation of thyroid hormone by deiodinases: local action with general consequences. Cell Mol Life Sci 2008; 65:570-90. [PMID: 17989921 PMCID: PMC11131710 DOI: 10.1007/s00018-007-7396-0] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The thyroid hormone plays a fundamental role in the development, growth, and metabolic homeostasis in all vertebrates by affecting the expression of different sets of genes. A group of thioredoxin fold-containing selenoproteins known as deiodinases control thyroid hormone action by activating or inactivating the precursor molecule thyroxine that is secreted by the thyroid gland. These pathways ensure regulation of the availability of the biologically active molecule T3, which occurs in a time-and tissue-specific fashion. In addition, because cells and plasma are in equilibrium and deiodination affects central thyroid hormone regulation, these local deiodinase-mediated events can also affect systemic thyroid hormone economy, such as in the case of non-thyroidal illness. Heightened interest in the field has been generated following the discovery that the deiodinases can be a component in both the Sonic hedgehog signaling pathway and the TGR-5 signaling cascade, a G-protein-coupled receptor for bile acids. These new mechanisms involved in deiodinase regulation indicate that local thyroid hormone activation and inactivation play a much broader role than previously thought.
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Kaneko M, Okada R, Yamamoto K, Nakamura M, Mosconi G, Polzonetti-Magni AM, Kikuyama S. Bisphenol A acts differently from and independently of thyroid hormone in suppressing thyrotropin release from the bullfrog pituitary. Gen Comp Endocrinol 2008; 155:574-80. [PMID: 17959175 DOI: 10.1016/j.ygcen.2007.09.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2007] [Revised: 07/15/2007] [Accepted: 09/03/2007] [Indexed: 11/21/2022]
Abstract
The objective of this investigation was to ascertain whether bisphenol A (BPA), which has a structural resemblance to thyroid hormone (TH), acts as a TH agonist or antagonist in terms of affecting the release of thyrotropin (TSH). To this end, we exposed adult bullfrog (Rana catesbeiana) pituitary cells to BPA and/or TH in the presence or absence of corticotropin-releasing factor (CRF), which is known to have a potent TSH-releasing activity in amphibians. BPA (10(-9)-10(-4)M) did not affect the basal release of TSH. However, it suppressed CRF-inducible TSH release at 10(-4)M, but not at 10(-5)M. Triiodothyronine (T(3)) at 10(-7)M and l-thyroxine (T(4)) at 10(-6)M also suppressed the CRF-inducible release of TSH. The combination of T(3) (10(-7)M) or T(4) (10(-6)M) with BPA (10(-4)M) had an additive effect in suppressing TSH release. A comparison of the suppressive effects of BPA and T(3) on the release of TSH following the addition of actinomycin D or cycloheximide to the culture medium revealed that both of the latter compounds blocked T(3)-inducible but not BPA-inducible suppression of TSH release. The results indicate that the mechanism of action of BPA is different from that of T(3) in that T(3) action involves RNA and protein synthesis, whereas BPA action does not involve either of these processes. Furthermore, BPA was found to suppress the thyrotropin-releasing hormone-inducible release of both prolactin (PRL) and TSH. Our results suggest that BPA acts not only as a blocker of TSH secretagogues but also as a blocker of a PRL secretagogue at the pituitary level. Estradiol affected neither the release of TSH nor the release of PRL in the presence or absence of their secretagogues, suggesting that the suppression of the release of TSH and PRL caused by BPA may not be derived from its estrogenic activity.
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Lucignani G. Long-term risks in hyperthyroid patients treated with radioiodine: is there anything new? Eur J Nucl Med Mol Imaging 2008; 34:1504-9. [PMID: 17665195 DOI: 10.1007/s00259-007-0509-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Du FY, Zhan P. [Time-dependent effects of pentabrominatefl diphenyl ethers on thyroid hormones and histological structure of thyroids in rats]. SICHUAN DA XUE XUE BAO. YI XUE BAN = JOURNAL OF SICHUAN UNIVERSITY. MEDICAL SCIENCE EDITION 2008; 39:98-100. [PMID: 18390211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
OBJECTIVE To study the time-dependent effects of pentabrominated diphenyl ethers on thyroid hormones and the histological structure of thyroids in rats. METHODS One hundred healthy 4-week-old SD rats were randomly divided into 10 groups. The rats in the experimental groups were orally administered with pentabrominated diphenyl ethers (BDE-99) at a dose of 60 mg/kg for 10, 15, 20, 30 and 40 days respectively, while the rats in the control groups received equal volumes of corn oil for the same periods of time. Serum FT4, FT3 and TSH were measured by radioimmunoassay. Sections of thyroids were dyed with hematoxylin-eosin (HE) to detect pathological alterations in thyroid tissues. RESULTS Decreased serum FT4 and FT3 and increased TSR were detected in the BDE-99 treated rats at DiS and D20. No significant differences of serum hormones were found between the experimental and control groups at D10, D30 and D40. The thyroid follicle epithelium of the BDE-99 treated rats proliferated into multiple-layer structure at DiS. At D20, proliferative plaque formed in local areas. Solid buds and follicles secondary to the solid buds were detected at D30 and D40. CONCLUSION BDE-99 leads to structural changes of thyroids, reduces serum FT4 and FT3 and increases TSR. The time-dependent effects are evident in a damage and compensate pattern.
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Giuliani C, Noguchi Y, Harii N, Napolitano G, Tatone D, Bucci I, Piantelli M, Monaco F, Kohn LD. The flavonoid quercetin regulates growth and gene expression in rat FRTL-5 thyroid cells. Endocrinology 2008; 149:84-92. [PMID: 17962351 DOI: 10.1210/en.2007-0618] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Quercetin is the most consumed flavonoid present in fruits and vegetables. There has been increased interest in the possible health benefits of quercetin and other flavonoids. Because it is reported that these compounds have some antithyroid properties, we were interested whether, and by what mechanism, quercetin might regulate thyroid cell growth and function. In this report we show that quercetin inhibits thyroid cell growth in association with inhibition of insulin-modulated phosphatidylinositol 3-kinase-Akt kinase activity. Furthermore, quercetin decreases TSH-modulated RNA levels of the thyroid-restricted gene sodium/iodide symporter (NIS). We associated down-regulation of NIS RNA levels with inhibition of iodide uptake at comparable quercetin concentrations and could show that the inhibitory effect of quercetin on NIS RNA levels and iodide uptake is reproduced by inhibitors of the phospholipase-A(2)/lipoxygenase pathway. The specific inhibitor of protein kinase A, H89, only partially inhibited TSH-increased NIS expression and did not reproduce the quercetin effect. The quercetin studies thus reveal that the phospholipase-A(2)/lipoxygenase pathway appears to play an important role in TSH regulation of NIS gene expression, whereas quercetin inhibition of growth appears to involve an effect on insulin/IGF-I-Akt signaling. The data raise the possibility that quercetin may be a novel disruptor of thyroid function, which has potential effects on, or use in, the therapy of thyroid diseases.
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Chen WJ, Ho WJ, Chang GJ, Chen ST, Pang JHS, Chou SH, Tsay PK, Kuo CT. Propylthiouracil, independent of its antithyroid effect, produces endothelium-dependent vasodilatation through induction of nitric oxide bioactivity. Atherosclerosis 2008; 196:383-390. [PMID: 17178124 DOI: 10.1016/j.atherosclerosis.2006.11.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 07/14/2006] [Accepted: 11/12/2006] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Propylthiouracil (PTU), independent of its antithyroid effect, is recently found to have a potent antiatherosclerotic effect. The aim of this study is to investigate whether PTU has a beneficial effect on endothelial function. METHODS AND RESULTS Ninety patients with a history of hyperthyroidism receiving either PTU (n=45) or methimazole (MMI) (n=45) during the euthyroid status were enrolled in this study. Brachial artery endothelium-dependent (flow-mediated dilatation [FMD]) and endothelium-independent (nitroglycerin-mediated dilatation) responses were assessed by high-resolution ultrasound image. Data for these two groups were compared with those of 41 healthy control subjects. The FMD values were significantly increased in patients maintained on PTU versus those in the MMI and control groups (9.3+/-4.4%, 3.4+/-2.5%, and 3.6+/-3.4%, respectively; P<0.01). Nitroglycerin-mediated dilatation had no significant difference between the PTU, MMI, and control groups (17.4+/-7.5%, 15.9+/-6.1%, and 17.5+/-6.8%, respectively; P=0.455). On multivariate analysis, no significant relationship was found between the FMD and thyroid hormone index levels. To further elucidate whether PTU has a direct effect on endothelial function, the effect of PTU on isolated segments of Sprague-Dawley rat aorta was studied. Vasodilatation induced by PTU was endothelium-dependent and could be blocked by pretreatment with nitric oxide (NO) inhibitors. PTU also increased NO formation in aortic segments. CONCLUSIONS This study demonstrated that PTU produced endothelium-dependent vasodilatation through thyroid-independent and NO-mediated mechanisms that may contribute to its beneficial effect on atherosclerosis.
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Panda S, Kar A. Amelioration of L-thyroxine-induced hyperthyroidism by coumarin (1,2-benzopyrone) in female rats. Clin Exp Pharmacol Physiol 2007; 34:1217-9. [PMID: 17880380 DOI: 10.1111/j.1440-1681.2007.04701.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
1. The efficacy of coumarin (1,2-benzopyrone) was examined for the regulation of hyperthyroidism in female rats. 2. Coumarin was administered (10 mg/kg per day for 15 days) to l-thyroxine (L-T(4))-induced hyperthyroid as well as to euthyroid rats and changes in serum concentrations of thyroid hormones and in associated parameters, such as serum cholesterol, activity of hepatic 5'-monodeiodinase (5'DI) and glucose-6-phosphatase (G-6-Pase), glycogen content, bodyweight and daily food consumption, were analysed. Simultaneously, changes in hepatic lipid peroxidation (LPO), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) were also investigated. 3. Although L-T(4) administration increased serum levels of thyroid hormones, the activity of hepatic 5'DI, G-6-Pase and LPO and daily food consumption, it decreased the level of serum cholesterol, hepatic glycogen content and the activities of anti-oxidant enzymes, such as SOD, CAT and GSH. 4. However, simultaneous administration of coumarin for 15 days to a group of hyperthyroid animals reversed most of the aforementioned changes, indicating its potential to ameliorate hyperthyroidism. Moreover, the drug did not increase, but rather decreased, hepatic LPO, suggesting its safe nature. 5. The present findings reveal a positive role for coumarin in the regulation of hyperthyroidism without any hepatotoxicity. It also appears that the test compound inhibits thyroid function at both a glandular level and at the level of peripheral conversion of T(4) to tri-iodothyronine.
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Li H, Richard K, McKinnon B, Mortimer RH. Effect of Iodide on Human Choriogonadotropin, Sodium-Iodide Symporter Expression, and Iodide Uptake in BeWo Choriocarcinoma Cells. J Clin Endocrinol Metab 2007; 92:4046-51. [PMID: 17726079 DOI: 10.1210/jc.2006-2358] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Active placental transport of maternal iodide by the thyroidal sodium iodide symporter (NIS) provides an essential substrate for fetal thyroid hormone synthesis. NIS is expressed in trophoblast and is regulated by human choriogonadotropin (hCG). In thyroid, iodide down-regulates expression of several genes including NIS. Placentas of iodine-deficient rats demonstrate up-regulation of NIS mRNA, suggesting a role for iodide in regulating placental NIS. OBJECTIVES AND METHODS The objectives were to examine effects of iodide on expression of NIS and hCG in BeWo choriocarcinoma cells. Gene expression was studied by quantitative real-time PCR. Effects on NIS protein expression were assessed by Western blotting. Functional activity of NIS was measured by (125)I uptake. Expression of hCG protein was assessed by immunoassay of secreted hormone. RESULTS Iodide inhibited NIS mRNA and membrane protein expression as well as (125)I uptake, which were paralleled by decreased betahCG mRNA expression and protein secretion. Iodide had no effects on pendrin expression. Addition of hCG increased NIS mRNA expression. This effect was partially inhibited by addition of iodide. The inhibitory effects of iodide on NIS mRNA expression were abolished by propylthiouracil and dithiothreitol. CONCLUSIONS We conclude that expression of placental NIS is modulated by maternal iodide. This may occur through modulation of hCG effects on NIS and hCG gene expression.
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Crescioli C, Cosmi L, Borgogni E, Santarlasci V, Gelmini S, Sottili M, Sarchielli E, Mazzinghi B, Francalanci M, Pezzatini A, Perigli G, Vannelli GB, Annunziato F, Serio M. Methimazole inhibits CXC chemokine ligand 10 secretion in human thyrocytes. J Endocrinol 2007; 195:145-55. [PMID: 17911406 DOI: 10.1677/joe-07-0240] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
CXC chemokine ligand 10 (CXCL10) plays a pivotal role in the self-perpetuation of the inflammatory processes in patients with autoimmune thyroid disease. Treatment with methimazole (MMI) reduces serum CXCL10 in patients with Graves' disease. In isolated human thyrocytes, tumor necrosis factor (TNF)alpha demonstrates a potent synergistic effect on interferon (IFN)gamma-induced CXCL10 secretion. We investigated the mechanism underlying the synergism between IFNgamma and TNFalpha and the effect of MMI on CXCL10 secretion in human thyrocytes. A peroxisome proliferator-activated receptor gamma agonist, rosiglitazone (RGZ), a known inhibitor of T helper 1 (Th1)-mediated responses, was also studied for comparison. Experiments were carried out in human thyrocytes isolated from internodular parenchyma of thyroid tissues derived from patients who had undergone surgery for multinodular goiter. ELISA was used to measure CXCL10 levels in culture supernatant. Flow cytometry was used to assess IFNgamma membrane receptor expression. Specific mRNA analysis was performed by Taqman real-time PCR. Immunofluorescence was performed to detect nuclear translocation of nuclear factor-kappaB (NF-kappaB). In human thyrocytes, the synergistic effect of TNFalpha with IFNgamma on CXCL10 secretion is due to the upregulation of IFNgamma receptor expression. MMI decreased cytokine-induced CXCL10 secretion by reducing TNFalpha-induced upregulation of the IFNgamma receptor. RGZ decreased the cytokine-induced CXCL10 secretion by impairing NF-kappaB translocation, without affecting IFNgamma receptor. MMI and RGZ targeted thyrocytes with the same pharmacological potency, likely acting throughout different mechanisms. Targeting T helper 1-mediated autoimmune thyroid disease with drugs that impair different intracellular pathways could be a novel pharmacological tool.
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115
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Nygaard B. Hyperthyroidism. Am Fam Physician 2007; 76:1014-1016. [PMID: 17956073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
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Varney AA, Schlenker EH. Thyroid status affects 5-HT2A receptor modulation of breathing before, during, and following exposure of hamsters to acute intermittent hypoxia. Am J Physiol Regul Integr Comp Physiol 2007; 293:R2070-80. [PMID: 17855493 DOI: 10.1152/ajpregu.00495.2007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The BIO 14.6 hamster (dystrophic), animal model of limb girdle muscular dystrophy, exhibits low plasma triiodothyronine levels, muscle weakness, and decreased breathing. After exposure to acute intermittent bouts of hypoxia, dystrophic hamsters depress ventilation relative to baseline resulting in ventilatory long-term depression (LTD). Control hamsters may increase ventilation relative to baseline resulting in ventilatory long-term facilitation (LTF). Serotonin (5-HT) receptors, especially the 5-HT(2A) subtype, are involved in the development of LTF. The purpose of this study was to evaluate the role of 5-HT(2A) receptors in ventilatory and metabolic responses before, during, and following intermittent hypoxia in eleven euthyroid, nine dystrophic, and eleven propylthiouracil (PTU)-induced hypothyroid male hamsters. Animals received subcutaneous injections of vehicle or 0.5 mg/kg MDL (5-HT(2A) receptor antagonist). Plethysmography was used to evaluate ventilatory responses of the three groups to air, five bouts of 5 min of 10% oxygen, each interspersed with 5 min of air, followed by 60 min of exposure to air. CO(2) production was measured using the flow-through method. Vehicle-treated dystrophic and PTU-treated hamsters exhibited LTD. MDL decreased body temperature in all groups. After MDL treatment, the euthyroid group exhibited LTD. MDL treatment in the dystrophic, but not in the PTU-treated hamsters, maintained tidal volume, but did not reverse LTD. CO(2) production was increased in the euthyroid group with MDL treatment. Thus, 5-HT(2A) receptors affect body temperature, ventilation, and metabolism in hamsters. The differential responses noted in this study may be in part dependent on thyroid hormone status.
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Kundu S, Roy S, De J, Biswas A, Pramanik M, Ray AK. Maintenance of homeostasis for thyroid hormone in the adult rat brain: possible involvement of a nuclear-mediated phenomenon. Neuroendocrinology 2007; 86:94-103. [PMID: 17703090 DOI: 10.1159/000107580] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 06/08/2007] [Indexed: 12/11/2022]
Abstract
During adult-onset peripheral hypothyroidism, the brain maintains normal levels of thyroid hormone for some time through a mechanism of 'central homeostasis'. Although onset, duration, and termination of such a homeostatic phenomenon have been recently evaluated in rat models, the mechanism behind remains unknown. During our investigation to understand the mechanism further, we injected the protein synthesis blockers actinomycin D and cycloheximide along with propylthiouracil to adult male rats during the days of onset (day 2) and termination (day 20) of the homeostatic mechanism. We evaluated synaptosomal T(3) level and neuronal Na(+)-K(+)-ATPase and acetylcholinesterase activities along with deiodinase II activity and cyclic adenosine monophosphate level in the cerebral cortex. The results indicated prevalence of unchanged or lower levels of synaptosomal T(3) on the 2nd and on the 20th day, respectively. Such a condition has been parallely supported by reflections in cerebrocortical deiodinase II activity and cyclic adenosine monophosphate levels. The activities of cerebrocortical synaptosomal Na(+)-K(+)-ATPase and acetylcholinesterase, which are the two important physiological parameters for neuronal function, have been found to be supportive of the involvement of a neuronal protein-mediated factor in the 'on' and 'off' reactions in central homeostasis during peripheral hypothyroidism. The results of our study indicate that the expression of 'central thyroid hormone homeostasis' is a genomic nuclear-mediated mechanism.
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Fini JB, Le Mevel S, Turque N, Palmier K, Zalko D, Cravedi JP, Demeneix BA. An in vivo multiwell-based fluorescent screen for monitoring vertebrate thyroid hormone disruption. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:5908-14. [PMID: 17874805 DOI: 10.1021/es0704129] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
There is a pressing need for high throughput methods to assess potential effects of endocrine disrupting chemicals (EDCs). released into the environment. Currently our ability to identify effects in vitro exceeds that for in vivo monitoring. However, only in vivo analysis provides the full spectrum of physiological impacts exerted by a given chemical. With the aim of finding a physiological system compatible with automatic plate reading we tested the capacity of early embryonic stage Xenopus laevis tadpoles to monitor thyroid hormone (TH) disruption. Fluorescent transgenic X. laevis embryos bearing a TH/bZIP-eGFP construct, placed in 96 well plates, were used for a physiological-based screen for potential TH signaling disruptors. Using stage NF-45 embryos (time of thyroid gland formation) allowed rapid detection of chemical interference with both peripheral TR signaling and production of endogenous TH. Nanomolar concentrations of TH receptor agonists could be detected within 72 h. Moreover, when testing against a 5nM T3 challenge, the effects of inhibitors of TH production were revealed, including inhibitors of TH synthesis, (methimazole: 1 mM or sodium perchlorate: 3.56 microM), as well as antagonists acting at the receptor level (NH3: 2 microM) and a deiodinase inhibitor (iopanoic acid: 10 microM). Finally, we show that the thyroid disrupting activities of BPA (10 microM) and TBBPA (1 microM) can also be detected in this rapid screening protocol. Finally, this noninvasive technology using an automatic reading system shows low variability (around 5%) and permits detection of subtle changes in signaling by EDCs that either inhibit or activate TH signaling in vivo.
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Liu H, Gramatica P. QSAR study of selective ligands for the thyroid hormone receptor β. Bioorg Med Chem 2007; 15:5251-61. [PMID: 17524652 DOI: 10.1016/j.bmc.2007.05.016] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Accepted: 05/04/2007] [Indexed: 12/17/2022]
Abstract
In this paper, an accurate and reliable QSAR model of 87 selective ligands for the thyroid hormone receptor beta 1 (TRbeta1) was developed, based on theoretical molecular descriptors to predict the binding affinity of compounds with receptor. The structural characteristics of compounds were described wholly by a large amount of molecular structural descriptors calculated by DRAGON. Six most relevant structural descriptors to the studied activity were selected as the inputs of QSAR model by a robust optimization algorithm Genetic Algorithm. The built model was fully assessed by various validation methods, including internal and external validation, Y-randomization test, chemical applicability domain, and all the validations indicate that the QSAR model we proposed is robust and satisfactory. Thus, the built QSAR model can be used to fast and accurately predict the binding affinity of compounds (in the defined applicability domain) to TRbeta1. At the same time, the model proposed could also identify and provide some insight into what structural features are related to the biological activity of these compounds and provide some instruction for further designing the new selective ligands for TRbeta1 with high activity.
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Dong H, Yauk CL, Williams A, Lee A, Douglas GR, Wade MG. Hepatic gene expression changes in hypothyroid juvenile mice: characterization of a novel negative thyroid-responsive element. Endocrinology 2007; 148:3932-40. [PMID: 17463053 DOI: 10.1210/en.2007-0452] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The molecular mechanisms involved in the response of developing mice to disruptions in maternal thyroid hormone (TH) homeostasis are poorly characterized. We used DNA microarrays to examine a broad spectrum of genes from the livers of mice rendered hypothyroid by treating pregnant mice from gestational d 13 to postnatal d 15 with 6-propyl-2-thiouracil in drinking water. Twenty-four individuals (one male and one female pup from six litters of control or 6-propyl-2-thiouracil treatment groups, respectively) were profiled using Agilent oligonucleotide microarrays. MAANOVA identified 96 differentially expressed genes (false discovery rate adjusted P < 0.1 and fold change > 2 in at least one gender). Of these, 72 genes encode proteins of known function, 15 of which had previously been identified as regulated by TH. Pathway analysis revealed these genes are involved in metabolism, development, cell proliferation, apoptosis, and signal transduction. An immediate-early response gene, Nr4a1 (nuclear receptor subfamily 4, group A, member 1), was up-regulated by 3-fold in hypothyroid juvenile mouse liver; treatment of HepG2 cells with T(3) resulted in down-regulation of Nr4a1. A potential thyroid response element -1218 to -1188 bp upstream of the promoter region of Nr4a1 was identified and demonstrated to bind TH receptor (TR)-alpha and TRbeta. Point mutation or deletion of the sequence containing the potential Nr4a1-thyroid response element in transient gene expression studies resulted in both higher basal expression and loss of T(3) regulatory capacity, suggesting that this site is responsible for the negative regulation of gene expression by TR and TH.
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Tsujio M, Watahiki Y, Yoshioka K, Mutoh K. Morphology of Thyroid Follicular Cells of Methimazole-treated Rats. Anat Histol Embryol 2007; 36:290-4. [PMID: 17617107 DOI: 10.1111/j.1439-0264.2007.00764.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thyroids of rats treated with methimazole (MMI) were analysed histologically, immunohistochemically and electron microscopically. Thyroids of MMI-treated rats displayed greater hypertrophy and were heavier than those of control rats. Thyroids of MMI-treated rats were composed of variant or small follicles and contained more columnar cells than those of control rats. Strong staining of thyroid granules by azocarmine G was evident in the apical regions of follicular cells from MMI-treated rats. Anti-thyroglobulin positivity was detected in the apical regions of follicular epithelial cells, especially those of MMI-treated rats. After application of a post-embedding method to detect thyroglobulin, colloidal gold particles were often observed in apical vesicles of MMI-treated rats. Our study suggests that apical vesicles may serve as markers of hyperthyroidism. When the functional state of the thyroid gland is known from histological analysis, use of the Azan stain could provide useful additional information.
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Elias AN, Barr RJ. Enhanced apoptosis in psoriatic plaques after treatment with propylthiouracil. Eur J Dermatol 2007; 17:353-4. [PMID: 17540660 DOI: 10.1684/ejd.2007.0229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
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Bittencourt CS, Azzolini AECS, Ferreira DA, Assis-Pandochi AI. Antibody responses in hyperthyroid rats. Int Immunopharmacol 2007; 7:989-93. [PMID: 17499202 DOI: 10.1016/j.intimp.2007.02.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 02/12/2007] [Accepted: 02/16/2007] [Indexed: 11/26/2022]
Abstract
This study evaluated antibody production against sheep red blood cells (SRBC) in hyperthyroid rats during treatment with triiodothyronine (T(3)). The immune response was evaluated by measuring plaque forming cells (PFC) in the spleen and by enzyme-linked immunosorbent assay (ELISA) in serum of male Wistar rats (180+/-10 g) treated with 25 mug/day of triiodotironine (T(3)) during 7-12 days and immunized with SRBC at the 8th day of treatment. The results showed that anti-SRBC antibody production was significantly decreased in animals treated for 12 days when compared to normal rats immunized with the same antigen, as evaluated by the two assays. These results show that in this experimental model hyperthyroidism decreases antibody response. We previously observed the opposite effect, that is, an increase in this response in hypothyroid rats resulting from the treatment with propylthyouracil, a blocker of thyroid hormone biosynthesis. It is suggested that antibody production is affected by thyroid hormone levels.
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Morgado I, Santos CRA, Jacinto R, Power DM. Regulation of transthyretin by thyroid hormones in fish. Gen Comp Endocrinol 2007; 152:189-97. [PMID: 17289043 DOI: 10.1016/j.ygcen.2006.12.017] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 11/30/2006] [Accepted: 12/26/2006] [Indexed: 10/23/2022]
Abstract
Transthyretin (TTR) is a thyroid hormone-binding protein (THBP) which in its tetrameric form transports thyroid hormones (THs), thyroxine (T(4)) and triiodothyronine (T(3)) in the blood of vertebrates. The principal site of production of TTR is the liver but in the sea bream TTR mRNA is also present in the heart, intestine and brain. The regulation of TTR is unstudied in fish and the normal circulating level of this THBP is unknown. The aim of the present study was to establish factors which regulate TTR production in fish. As a first step a number of tools were generated; sea bream recombinant TTR (sbrTTR) and specific sbrTTR antisera which were used to establish an ELISA (enzyme-linked immunosorbent assay) for measuring TTR plasma levels. Subsequently, an experiment was conducted to determine the influence of THs on TTR production. Circulating physiological levels of TTR in sea bream determined by ELISA are approximately 3.8microgml(-1). Administration of T(3) and T(4) to sea bream significantly increased (p<0.001 and p<0.005, respectively) the concentration of circulating TTR ( approximately or = 11.5microgml(-1)) in relation to control fish, but did not change gene transcription in the liver. Methimazol (MMI) an antithyroid agent, failed to significantly reduce circulating THs below control levels but significantly increased (p<0.005) plasma TTR levels (approximately or = 10.8microgml(-1)) and decreased (p<0.05) transcription in the liver. Future studies will aim to elucidate in more detail these regulatory pathways.
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Abstract
Thyroid hormones (THs) have important effects on cellular development, growth, and metabolism. They bind to thyroid hormone receptors (TRs), TRalpha and TRbeta, which belong to the nuclear hormone receptor superfamily. These receptors also bind to enhancer elements in the promoters of target genes, and can regulate both positive and negative transcription. Recent emerging evidence has characterized some of the molecular mechanisms by which THs regulate transcription as co-repressors, and co-activators have been identified and their effects on histone acetylation examined. THs also have rapid effects that do not require transcription. These can occur via TRs or other cellular proteins, and typically occur outside the nucleus. It appears that THs regulate multiple cellular functions using a diverse array of receptors and signaling systems. TR isoform- or pathway-specific drugs might provide the therapeutic benefits of TH action such as decreasing obesity or lowering cholesterol levels without some of the side effects of hyperthyroidism.
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