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Hashida Y, Mino Y, Okuno K, Uemasu H, Sakata S, Fujimoto M, Namba N. Thyroid hormone may predict treatment failure in Kawasaki disease. Pediatr Int 2024; 66:e15723. [PMID: 38326932 DOI: 10.1111/ped.15723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 11/03/2023] [Accepted: 11/08/2023] [Indexed: 02/09/2024]
Abstract
BACKGROUND In systemic inflammatory conditions, inflammatory cytokines can cause low thyroid hormone levels. There are no reports discussing the relation between thyroid hormone levels and response to treatment for Kawasaki disease. METHODS We investigated 67 patients who underwent treatment in the acute phase of Kawasaki disease. We divided patients into two groups based on their response to initial intravenous immunoglobulin (IVIG) treatment: the responder group (n = 40), and the non-responder group (n = 27). The serum levels of the thyroid hormones free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) were compared before and after treatment in all patients, and between responder and non-responder groups. RESULTS The FT3, FT4, and TSH levels were low before the initial treatment and increased significantly after treatment (p < 0.05). The FT3, FT4, and TSH levels before treatment were significantly lower in the non-responder group than in the responder group (p < 0.05). Logistic regression analysis suggested that the addition of pre-treatment FT4 values to Gunma score was useful in predicting treatment failure. CONCLUSIONS Thyroid hormone and TSH levels were lower in the non-responder group than in the responder group in the initial IVIG treatment for Kawasaki disease. This study suggests that Kawasaki disease in the acute phase is associated with low thyroid hormone levels and TSH. It is possible that these hormone levels predict response to the initial IVIG.
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Affiliation(s)
- Yuichiro Hashida
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
- Department of Pediatrics, Tottori Prefectural Kousei Hospital, Kurayoshi, Japan
| | - Yoichi Mino
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
| | - Keisuke Okuno
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
| | - Hitoshi Uemasu
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
| | - Shinji Sakata
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
| | - Masanobu Fujimoto
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
| | - Noriyuki Namba
- Division of Pediatrics and Perinatology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago, Japan
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Hepatic Energy Metabolism under the Local Control of the Thyroid Hormone System. Int J Mol Sci 2023; 24:ijms24054861. [PMID: 36902289 PMCID: PMC10002997 DOI: 10.3390/ijms24054861] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 02/24/2023] [Accepted: 02/25/2023] [Indexed: 03/06/2023] Open
Abstract
The energy homeostasis of the organism is orchestrated by a complex interplay of energy substrate shuttling, breakdown, storage, and distribution. Many of these processes are interconnected via the liver. Thyroid hormones (TH) are well known to provide signals for the regulation of energy homeostasis through direct gene regulation via their nuclear receptors acting as transcription factors. In this comprehensive review, we summarize the effects of nutritional intervention like fasting and diets on the TH system. In parallel, we detail direct effects of TH in liver metabolic pathways with regards to glucose, lipid, and cholesterol metabolism. This overview on hepatic effects of TH provides the basis for understanding the complex regulatory network and its translational potential with regards to currently discussed treatment options of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) involving TH mimetics.
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Jurado-Flores M, Warda F, Mooradian A. Pathophysiology and Clinical Features of Neuropsychiatric Manifestations of Thyroid Disease. J Endocr Soc 2022; 6:bvab194. [PMID: 35059548 PMCID: PMC8765786 DOI: 10.1210/jendso/bvab194] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Indexed: 01/25/2023] Open
Abstract
Thyroid hormones (TH) have a cardinal role in the development of the central nervous system during embryogenesis and early infancy. However, the TH-responsive genes in the developing brain cease to respond to TH in adulthood. Nevertheless, thyroid dysfunction in adults is commonly associated with a host of cognitive and psychiatric problems. Cognitive decline, dysphoria, and depression are common manifestations of overt hypothyroidism while hyperthyroidism can cause agitation, acute psychosis, and apathy, especially in older people. Whereas levothyroxine treatment can reverse dementia in the setting of hypothyroidism, the effect of levothyroxine on depressive symptoms in subjects with subclinical hypothyroidism is controversial. The use of supraphysiologic doses of TH to treat depression refractory to antidepressant remains a viable therapeutic tool with the caveat that excessive doses of thyroid hormone to treat depression may have potentially damaging effects on other organ systems. The present communication describes the pathophysiology of neuropsychiatric manifestations of thyroid disease, including changes in neurotransmission, alterations in neuronal or glial cell gene expression, blood-brain barrier dysfunction, increased risk of cerebrovascular disease, and occasionally cerebral inflammatory disease in the context of autoimmune thyroid disease. Elucidating the molecular mechanisms of TH effect on cerebral tissue will help identify novel therapeutic targets for managing people with neuropsychiatric disorders.
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Affiliation(s)
- Marilu Jurado-Flores
- Division of Endocrinology, Department of Medicine, University of Florida College of Medicine, Jacksonville, FL 32209, USA
| | - Firas Warda
- Division of Endocrinology, Department of Medicine, University of Florida College of Medicine, Jacksonville, FL 32209, USA
| | - Arshag Mooradian
- Division of Endocrinology, Department of Medicine, University of Florida College of Medicine, Jacksonville, FL 32209, USA
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4
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Kuś A, Kjaergaard AD, Marouli E, Fabiola Del Greco M, Sterenborg RB, Chaker L, Peeters RP, Bednarczuk T, Åsvold BO, Burgess S, Deloukas P, Teumer A, Ellervik C, Medici M. Thyroid Function and Mood Disorders: A Mendelian Randomization Study. Thyroid 2021; 31:1171-1181. [PMID: 33899528 PMCID: PMC7612998 DOI: 10.1089/thy.2020.0884] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Background: Observational studies suggest that even minor variations in thyroid function are associated with the risk of mood disorders, including major depressive disorder (MDD) and bipolar disorder (BD). However, it is unknown whether these associations are causal or not. We used a Mendelian randomization (MR) approach to investigate causal effects of minor variations in thyrotropin (TSH) and free thyroxine (fT4) levels on MDD and BD risk. Materials and Methods: We performed two-sample MR analyses using data from the largest publicly available genome-wide association studies on normal-range TSH (n = 54,288) and fT4 (n = 49,269) levels, MDD (170,756 cases, 329,443 controls) and BD (20,352 cases, 31,358 controls). Secondary MR analyses investigated the effects of TSH and fT4 levels on specific MDD and BD subtypes. Reverse MR was also performed to assess the effects of MDD and BD on TSH and fT4 levels. Results: There were no associations between genetically predicted TSH and fT4 levels and MDD risk, nor MDD subtypes and minor depressive symptoms. A one standard deviation increase in fT4 levels was nominally associated with an 11% decrease in the overall BD risk (odds ratio [OR] = 0.89, 95% confidence interval [CI] = 0.80-0.98, p = 0.022) and a 13% decrease in the BD type 1 risk (OR = 0.87, CI = 0.75-1.00, p = 0.047). In the reverse direction, genetic predisposition to MDD and BD was not associated with TSH nor fT4 levels. Conclusions: Variations in normal-range TSH and fT4 levels have no effects on the risk of MDD and its subtypes, and neither on minor depressive symptoms. This indicates that depressive symptoms should not be attributed to minor variations in thyroid function. Borderline associations with BD and BD type 1 risks suggest that further clinical studies should investigate the effect of thyroid hormone treatment in BD.
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Affiliation(s)
- Aleksander Kuś
- Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus Medical Center, Dr. Molewaterplein 40, 3015 CE Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
- Department of Internal Medicine and Endocrinology, Medical University of Warsaw, Banacha 1a, 02-097 Warsaw, Poland
| | - Alisa D. Kjaergaard
- Steno Diabetes Center Aarhus, Aarhus University Hospital, Hedeager 3, 8000 Aarhus, Denmark
| | - Eirini Marouli
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ London, UK
- Centre for Genomic Health, Life Sciences, Queen Mary University of London, EC1M 6BQ London, UK
| | - M. Fabiola Del Greco
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lubeck, Via Galvani 31, 39100 Bolzano, Italy
| | - Rosalie B.T.M. Sterenborg
- Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus Medical Center, Dr. Molewaterplein 40, 3015 CE Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
- Department of Internal Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, The Netherlands
| | - Layal Chaker
- Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus Medical Center, Dr. Molewaterplein 40, 3015 CE Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
| | - Robin P. Peeters
- Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus Medical Center, Dr. Molewaterplein 40, 3015 CE Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
| | - Tomasz Bednarczuk
- Department of Internal Medicine and Endocrinology, Medical University of Warsaw, Banacha 1a, 02-097 Warsaw, Poland
| | - Bjørn O. Åsvold
- K.G. Jebsen Center for Genetic Epidemiology, NTNU, Norwegian University of Science and Technology, Post box 8905, 7491 Trondheim, Norway
- Department of Endocrinology, St. Olavs Hospital, Trondheim University Hospital, Prinsesse Kristinas gate 3, 7030 Trondheim, Norway
| | - Stephen Burgess
- MRC Biostatistics Unit, Cambridge Institute of Public Health, University of Cambridge, Forvie Site, Robinson Way, Cambridge, CB2 0SR, UK
- Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, 2 Worts Causeway, Cambridge CB1 8RN, UK
| | - Panos Deloukas
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ London, UK
- Centre for Genomic Health, Life Sciences, Queen Mary University of London, EC1M 6BQ London, UK
- Princess Al-Jawhara Al-Brahim Centre of Excellence in Research of Hereditary Disorders (PACER-HD), King Abdulaziz University, Jeddah, Saudi Arabia
| | - Alexander Teumer
- Institute for Community Medicine, University Medicine Greifswald, W.-Rathenau-Str. 48, 17475 Greifswald, Germany
- DZHK (German Center for Cardiovascular Research), partner site Greifswald, Fleischmannstr. 8, 17475 Greifswald, Germany
| | - Christina Ellervik
- Department of Laboratory Medicine, Boston Children's Hospital, 300 Longwood Avenue, Boston, 02115 MA, USA
- Harvard Medical School, 25 Shattuck St, Boston, MA 02115, USA
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Nørre Alle 41, 2200 Copenhagen, Denmark
| | - Marco Medici
- Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus Medical Center, Dr. Molewaterplein 40, 3015 CE Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
- Department of Internal Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, The Netherlands
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Abstract
PURPOSE OF REVIEW This review summarizes recent literature on nonthyroidal illness syndrome (NTI) and outcome of pediatric critical illness, to provide insight in pathophysiology and therapeutic implications. RECENT FINDINGS NTI is typically characterized by lowered triiodothyronine levels without compensatory TSH rise. Although NTI severity is associated with poor outcome of pediatric critical illness, it remains unclear whether this association reflects an adaptive protective response or contributes to poor outcome. Recently, two metabolic interventions that improved outcome also altered NTI in critically ill children. These studies shed new light on the topic, as the results suggested that the peripheral NTI component, with inactivation of thyroid hormone, may represent a beneficial adaptation, whereas the central component, with suppressed TSH-driven thyroid hormone secretion, may be maladaptive. There is currently insufficient evidence for treatment of NTI in children. However, the recent findings raised the hypothesis that reactivation of the central NTI component could offer benefit, which should be tested in RCTs. SUMMARY NTI in critically ill children can be modified by metabolic interventions. The peripheral, but not the central, component of NTI may be a beneficial adaptive response. These findings open perspectives for the development of novel strategies to improve outcome of critical illness in children.
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Affiliation(s)
- An Jacobs
- Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, KU Leuven University Hospital, Leuven, Belgium
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6
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Siroen MPC, van Bokhorst-de van der Schueren MAE, Richir MC, Sauerwein HP, Leemans CR, Quak JJ, van Leeuwen PAM. The Prognostic Value of Severe Malnutrition in the Development of Nonthyroidal Illness in Head and Neck Cancer Patients. JPEN J Parenter Enteral Nutr 2017; 30:415-20. [PMID: 16931610 DOI: 10.1177/0148607106030005415] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Thyroid hormone metabolism is modulated by starvation and overfeeding but also by dietary composition. Unfortunately, little is known about the effect of malnutrition on disease-induced nonthyroidal illness (NTI). In this study, we investigated whether the degree of NTI after surgery differed between severely malnourished and well-fed patients with head and neck cancer. METHODS Plasma levels of the thyroid hormones 3',5-triiodothyronine (T(3)), reverse T(3) (rT(3)), free T(4) (FT(4)), and thyrotropin (TSH) were measured on the first day before the operation and on the first, fourth, and seventh day after the operation in 16 malnourished patients who were admitted for intentional curative surgery of T1-T4 carcinomas of the head and neck. Six well-fed head and neck cancer patients eligible for surgical treatment served as a control group. RESULTS In the malnourished group, rT(3) showed a significant increase, whereas T(3) and FT(4) decreased significantly due to the operation. TSH showed no significant change. During the postoperative course, it took 7 days until rT(3) and 4 days until T(3) and FT(4) were restored to their preoperative value. In contrast, well-fed patients did not develop NTI. CONCLUSIONS This study shows that peri- and postoperative rT(3), T(3), and FT(4) levels change significantly in malnourished patients compared with well-fed patients. Therefore, it can be concluded that nutrition status of patients undergoing major head and neck surgery should be optimized in order to prevent the development of NTI.
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Affiliation(s)
- M P C Siroen
- Department of Surgery, VU University Medical Center, Amsterdam, The Netherlands
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7
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Kelly T. A hypothesis on the mechanism of action of high-dose thyroid in refractory mood disorders. Med Hypotheses 2016; 97:16-21. [PMID: 27876122 DOI: 10.1016/j.mehy.2016.09.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 09/24/2016] [Accepted: 09/27/2016] [Indexed: 12/21/2022]
Abstract
Multiple lines of evidence suggest the hypothesis that high dose thyroid therapy corrects for cellular hypothyroidism found in bipolar disorders. Evidence indicates that bipolar disorders are associated with mitochondrial dysfunction which results in low cellular adenosine 5'-triphosphate (ATP) levels. Transport of thyroid hormones into cells is energy intensive and dependent on ATP except in the pituitary gland. Inadequate ATP levels makes it difficult to get thyroid hormone into cells leading to cellular hypothyroidism. This creates a condition where the blood and pituitary levels of thyroid hormone are normal but low in other tissues. High dose thyroid therapy produces a gradient that is sufficient for thyroid hormone to diffuse into cells correcting cellular hypothyroidism. If this hypothesis is correct there are number of implications. The two most important are: On average patients suffering from a bipolar disorder die 10-20years earlier than the general population. The medical sequelae associated with bipolar disorders cause far more deaths than suicide. If high dose thyroid corrects for cellular hypothyroidism it could well decrease the medical morbidity and mortality associated with bipolar disorders that are the result of cellular hypothyroidism. Thus high dose thyroid would be a first treatment that decreases the considerable medical morbidity and mortality associated with the bipolar disorders. This would stand in stark contrast to most psychiatric medications that can that increase morbidity and mortality. It would also reinforce the safety of HDT. The second implication is thyroid hormone blood levels in patients suffering from a bipolar disorder do not accurately reflect the true thyroid status.
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Affiliation(s)
- Tammas Kelly
- George Washington University, GWU MFA Department of Psychiatry and Behavioral Sciences, 2120 L St NW, Suite 600, Washington DC 20037, United States; The Depression & Bipolar Clinic of Colorado, 400 East Horsetooth Road, Suite 300, Fort Collins, Colorado 80525, United States.
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8
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Abstract
BACKGROUND Critically ill patients typically present with low or low-normal plasma thyroxine, low plasma triiodothyronine (T3), increased plasma reverse T3 (rT3) concentrations, in the absence of a rise in thyrotropin (TSH). This constellation is referred to as nonthyroidal illness syndrome (NTI). Although it is long known that the severity of NTI is associated with risk of poor outcomes of critical illness, the causality in this association has not been well investigated. SUMMARY In this narrative review, the different faces of NTI during critical illness are highlighted. Acute alterations are dominated by changes in thyroid hormone binding, peripheral thyroid hormone uptake, and alterations in the expression and activity of the type-1 and type-3 deiodinases. It was recently shown that at least part of these acute changes are brought about by concomitant macronutrient restriction, and this part appears adaptive and beneficial. However, the face of the NTI in the prolonged phase of critical illness is different, when patients are fully fed but continue to depend on intensive medical care. In that prolonged phase of illness, hypothalamic thyrotropin releasing hormone (TRH) expression is suppressed and explains reduced TSH secretion and whereby reduced thyroidal hormone release. During prolonged critical illness, and in the presence of adequate nutrition, several tissue responses could be interpreted as compensatory to low thyroid hormone availability, such as increased expression of monocarboxylate transporters, upregulation of type-2 deiodinase activity, and increased sensitivity at the receptor level. Infusing hypothalamic releasing factors in these prolonged critically ill patients can reactivate the thyroid axis and induce an anabolic response. CONCLUSIONS It is clear that the name "NTI" during critical illness refers to a syndrome with different faces. Tolerating the early "fasting response" to critical illness and its concomitant changes in thyroid hormone parameters appears to be wise and beneficial. This thus applies to the NTI present in the majority of the patients treated in intensive care units. However, the NTI that occurs in prolonged critically ill patients appears different with regard to both its causes and consequences. Future studies should specifically target this selected population of prolonged critically ill patients, and, after excluding iatrogic drug interferences, investigate the effect on outcome of treatment with hypothalamic releasing factors in adequately powered randomized controlled trials.
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Affiliation(s)
- Greet Van den Berghe
- Clinical Division and Laboratory of Intensive Care Medicine , Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
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9
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Abstract
Thyroid hormones are extremely important for metabolism, development, and growth during the lifetime. The hypothalamo-pituitary-thyroid axis is precisely regulated for these purposes. Much of our knowledge of this hormonal axis is derived from experiments in animals and mutations in man. This review examines the hypothalamo-pituitary-thyroid axis particularly in relation to the regulated 24-hour serum TSH concentration profiles in physiological and pathophysiological conditions, including obesity, primary hypothyroidism, pituitary diseases, psychiatric disorders, and selected neurological diseases. Diurnal TSH rhythms can be analyzed with novel and precise techniques, eg, operator-independent deconvolution and approximate entropy. These approaches provide indirect insight in the regulatory components in pathophysiological conditions.
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Affiliation(s)
- Ferdinand Roelfsema
- Leiden University Medical Center, Department of Endocrinology and Metabolic Diseases, PO Box 9600, 2300 RC Leiden, The Netherlands.
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10
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Abstract
BACKGROUND Musculoskeletal complaints are common in patients with thyroid dysfunction. Both thyrotoxic and hypothyroid myopathy have been well described, and there are distinct presentations, laboratory findings, and clinical outcomes between the two groups. Myopathy has also been reported in hyperthyroid patients only after beginning treatment, suggesting that relative hypothyroidism may also contribute to musculoskeletal disease. A confounding factor in these cases was that these patients were on antithyroid drugs that may also have direct effects on the muscle, irrespective of the rate of decline in thyroid hormone levels. SUMMARY We report a patient with Graves' disease who developed myalgias with elevated creatine kinase levels after total thyroidectomy. Addition of triiodothyronine quickly resolved her symptoms and creatine kinase levels, whereas discontinuation of triiodothyronine, despite having normal to elevated total thyroxine levels, led to a relapse. CONCLUSION Myositis after correction of thyrotoxicosis may constitute a syndrome that should be assessed for in hyperthyroid patients complaining of myalgias after starting treatment.
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Affiliation(s)
- Duha Shaheen
- Division of Endocrinology, Diabetes, and Metabolism, Tufts Medical Center , Boston, Massachusetts, USA
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11
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Hennemann G, Krenning EP. The kinetics of thyroid hormone transporters and their role in non-thyroidal illness and starvation. Best Pract Res Clin Endocrinol Metab 2007; 21:323-38. [PMID: 17574011 DOI: 10.1016/j.beem.2007.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kinetic tracer studies show that thyroid hormones are transported into target tissues by stereospecific, high-affinity, low-capacity transporters, both in animals and humans. The K(d) of binding to the transporter varies within the nanomolar range. The different thyroid hormones (T(4), T(3), and rT(3)) are transported via different transporters, except in the pituitary, where they share the same transporter. The molecular mass of the transport proteins varies between 52 and 65kDa. The transport mechanisms are dependent on the energy charge of the cell and -- often -- the sodium gradient over the plasma membrane. A relationship exists with the transport systems of the aromatic amino acids. In non-thyroidal illness and starvation T(4) transport into T(3)-producing tissues is decreased, resulting in a low plasma T(3) concentration, by some considered to be an energy saving mechanism in situations of stress.
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12
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Peeters RP, Debaveye Y, Fliers E, Visser TJ. Changes within the thyroid axis during critical illness. Crit Care Clin 2006; 22:41-55, vi. [PMID: 16399019 DOI: 10.1016/j.ccc.2005.08.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Pronounced alterations in plasma thyroid stimulating hormone and thyroid hormone levels occur during critical illness without any evidence for thyroid disease. Plasma T3 decreases and plasma rT3 increases within a few hours after the onset of disease, and the magnitude of these changes is related to the severity and the duration of the disease. This article reviews the mechanisms behind the observed changes, and focuses on the regulation of thyroid hormone deiodination and transport, as well as the potential positive or negative effects for both the acute and the chronic phase of critical illness.
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Affiliation(s)
- Robin P Peeters
- Department of Internal Medicine, Room Ee 502, Erasmus University Medical Center, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands.
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Decuypere E, Van As P, Van der Geyten S, Darras VM. Thyroid hormone availability and activity in avian species: a review. Domest Anim Endocrinol 2005; 29:63-77. [PMID: 15890488 DOI: 10.1016/j.domaniend.2005.02.028] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Revised: 02/24/2005] [Accepted: 02/24/2005] [Indexed: 12/31/2022]
Abstract
The intracellular thyroid hormone (TH) availability is influenced by different metabolic pathways. Some of the changes in intracellular TH availability can be linked to changes in local deiodination and sulfation capacities. The secretion of the chicken thyroid consists predominantly of thyroxine (T4). TH receptors (TRs) preferentially bind 3,5,3'-triiodothyronine (T3). Therefore, the metabolism of T4 secreted by the thyroid gland in peripheral tissues, resulting in the production and degradation of receptor-active T3, plays a major role in thyroid function. Food restriction in growing chickens increases hepatic type III deiodinase (D3) levels but decreases growth hormone (GH)-dependent variables such as plasma insulin-like growth factor-I (IGF-I) and T3 concentrations. Refeeding restores hepatic D3 and plasma T3 to control levels within a few hours. It can be concluded that the tissue and time dependent regulation of the balance between TH activating and inactivating enzymes plays an essential role in the control of local T3 availability and hence in TH activity. Two separate genes encode multiple TR isoforms, i.e. TRalpha and TRbeta. These TRs consist of a DNA-binding domain, a ligand-binding domain, a hinge region and an amino-terminal (A/B) domain. TRs mediate their effects on transcription by binding as homodimers or heterodimers to the TH response elements (TREs). Also, unliganded TRs can bind to TREs and may so modulate transcription of target genes.
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Affiliation(s)
- E Decuypere
- Laboratory for Physiology and Immunology of Domestic Animals, Department of Animal Production, Katholieke Universiteit Leuven, Kasteelpark Arenberg 30, B-3001 Leuven, Belgium.
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15
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Mishra MK, Wilson FE, Scanlan TS, Chiellini G. Thyroid hormone-dependent seasonality in American tree sparrows (Spizella arborea): effects of GC-1, a thyroid receptor beta-selective agonist, and of iopanoic acid, a deiodinase inhibitor. J Comp Physiol B 2004; 174:471-9. [PMID: 15235810 DOI: 10.1007/s00360-004-0433-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2004] [Indexed: 10/26/2022]
Abstract
To explore the role of TH in the control of seasonality [i.e., photoperiodic testicular growth, photorefractoriness, and postnuptial (prebasic) molt] in American tree sparrows (Spizella arborea), we performed experiments in which THX males were simultaneously photostimulated and given TH replacement therapy. In the first experiment, equimolar concentrations (1X = 1.3 nmol) of T4, T3, or GC-1, an iodine-free TRbeta agonist, were administered s.c. daily during the first 21 days of photostimulation. Two additional THX groups received GC-1 at 0.1X or 10X, and THX and THI control groups received vehicle. In the second experiment, T4 or T3, alone or in combination with the deiodinase inhibitor IOP, was injected i.m. twice daily during the first 14 days of photostimulation. In both experiments, end points were testis length and molt score. In the first experiment, THI birds given vehicle and THX birds given T4 replacement therapy exhibited all three components of seasonality. THX birds given T3 or GC-1 (1X or 10X) showed a subdued photoperiodic testicular response, but they did not become photorefractory or initiate molt. THX birds that received 0.1X GC-1 or vehicle exhibited none of the components of seasonality. These data are consistent with the hypothesis that photoperiodic testicular growth, a vernal component of seasonality, is a TRbeta-mediated response and suggest that T4 may activate TRbeta more efficiently than does T3 or GC-1. By contrast, the failure both of T3 and of GC-1, but not of T4, to program photostimulated THX males for photorefractoriness and postnuptial molt suggests that autumnal components of seasonality may be TRalpha-mediated responses solely to T4. In the second experiment, IOP administered alone had no significant impact on seasonality. THX birds that received T4 with or without IOP showed all components of seasonality, whereas birds that received T3 with or without IOP showed only photoperiodic testicular growth. These results challenge the widely held view that T4 is merely a prohormone for T3 and support the emerging view that T4 has intrinsic hormonal activity. Because IOP augmented the photoperiodic testicular response in T3-treated THX birds, T3 may act either independently or co-dependently with T4 in programming vernal seasonal events.
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Affiliation(s)
- M K Mishra
- Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
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16
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Meston N, Davies RJO, Mullins R, Jenkinson C, Wass JAH, Stradling JR. Endocrine effects of nasal continuous positive airway pressure in male patients with obstructive sleep apnoea. J Intern Med 2003; 254:447-54. [PMID: 14535966 DOI: 10.1046/j.1365-2796.2003.01212.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Obstructive sleep apnoea (OSA) is a relatively common condition producing disabling somnolence and profound physiological responses to hypoxaemic episodes during sleep, including significant oscillations in blood pressure. This study aimed to provide controlled data on the interaction between OSA and endocrine axes to establish whether overrepresentation of pathology such as hypertension and hypogonadism in OSA subjects might have an endocrine basis. DESIGN, SETTING AND SUBJECTS Parallel randomized sham placebo controlled 1-month trial of nasal continuous positive airway pressure (nCPAP) in 101 male subjects with OSA presenting to a respiratory sleep clinic. METHODS Analysis of gonadotrophins, testosterone, sex hormone binding protein (SHBG), prolactin, cortisol, thyroid stimulating hormone (TSH), free thyroxine (free T4), insulin-like growth factor-1 (IGF-1), renin and aldosterone were performed at baseline and after 1 month's active or placebo nCPAP intervention. Quality of life questionnaire scoring was also recorded over the same time period. RESULTS Testosterone and SHBG showed significant negative correlations with baseline OSA severity. Active treatment of OSA produced SHBG elevation and TSH reduction (P< or =0.03). Both groups showed an increase in aldosterone (P<0.001) and IGF-1 (P< or =0.03), associated with a large improvement in subjective quality of life scoring. CONCLUSIONS These findings demonstrate significant changes in endocrine axes not previously reported in a placebo-controlled trial. OSA is a recognized reversible cause of testosterone reduction; SHBG suppression correlating to baseline OSA severity supports a diagnosis of secondary hypogonadism. Significant rises in aldosterone and IGF-1 on treatment coincide with increased physical activity and an improved quality of life score.
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Affiliation(s)
- N Meston
- Department of Clinical Laboratory Sciences, University of Oxford, John Radcliffe Hospital, Oxford, UK.
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17
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Peeters RP, Friesema ECH, Docter R, Hennemann G, Visser TJ. Effects of thyroid state on the expression of hepatic thyroid hormone transporters in rats. Am J Physiol Endocrinol Metab 2002; 283:E1232-8. [PMID: 12388169 DOI: 10.1152/ajpendo.00214.2002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Liver uptake of thyroxine (T4) is mediated by transporters and is rate limiting for hepatic 3,3',5-triiodothyronine (T3) production. We investigated whether hepatic mRNA for T4 transporters is regulated by thyroid state using Xenopus laevis oocytes as an expression system. Because X. laevis oocytes show high endogenous uptake of T4, T4 sulfamate (T4NS) was used as an alternative ligand for the hepatic T4 transporters. Oocytes were injected with 23 ng liver mRNA from euthyroid, hypothyroid, or hyperthyroid rats, and after 3-4 days uptake was determined by incubation of injected and uninjected oocytes for 1 h at 25 degrees C or for 4 h at 18 degrees C with 10 nM [125I]T4NS. Expression of type I deiodinase (D1), which is regulated by thyroid state, was studied in the oocytes as an internal control. Uptake of T4NS showed similar approximately fourfold increases after injection of liver mRNA from euthyroid, hypothyroid, or hyperthyroid rats. A similar lack of effect of thyroid state was observed using reverse T3 as ligand. In contrast, D1 activity induced by liver mRNA from hyperthyroid and hypothyroid rats in the oocytes was 2.4-fold higher and 2.7-fold lower, respectively, compared with euthyroid rats. Studies have shown that uptake of iodothyronines in rat liver is mediated in part by several organic anion transporters, such as the Na+/taurocholate-cotransporting polypeptide (rNTCP) and the Na-independent organic anion-transporting polypeptide (rOATP1). Therefore, the effects of thyroid state on rNTCP, rOATP1, and D1 mRNA levels in rat liver were also determined. Northern analysis showed no differences in rNTCP or rOATP1 mRNA levels between hyperthyroid and hypothyroid rats, whereas D1 mRNA levels varied widely as expected. These results suggest little effect of thyroid state on the levels of mRNA coding for T4 transporters in rat liver, including rNTCP and rOATP1. However, they do not exclude regulation of hepatic T4 transporters by thyroid hormone at the translational and posttranslational level.
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Affiliation(s)
- Robin P Peeters
- Departments of Internal Medicine and Nuclear Medicine, Erasmus University Medical Center, 3000 DR Rotterdam, The Netherlands
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Schmidt JM, Ostermayr B. Does a homeopathic ultramolecular dilution of Thyroidinum 30cH affect the rate of body weight reduction in fasting patients? A randomised placebo-controlled double-blind clinical trial. HOMEOPATHY 2002; 91:197-206. [PMID: 12422922 DOI: 10.1054/homp.2002.0049] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE To test whether an ultramolecular dilution of homeopathic Thyroidinum has an effect over placebo on weight reduction of fasting patients in so-called 'fasting crisis'. DESIGN Randomised, placebo-controlled, double-blind, parallel group, monocentre study. SETTING/LOCATION Hospital for internal and complementary medicine in Munich, Germany. SUBJECTS Two hundred and eight fasting patients encountering a stagnation or increase of weight after a weight reduction of at least 100 g/day in the preceding 3 days. INTERVENTION One oral dose of Thyroidinum 30cH (preparation of thyroid gland) or placebo. OUTCOME MEASURES Main outcome measure was reduction of body weight 2 days after treatment. Secondary outcome measures were weight reduction on days 1 and 3, 15 complaints on days 1-3, and 34 laboratory findings on days 1-2 after treatment. RESULTS Weight reduction on the second day after medication in the Thyroidinum group was less than in the placebo group (mean difference 92 g, 95% confidence interval 7-176 g, P=0.034). Adjustment for baseline differences in body weight and rate of weight reduction before medication, however, weakened the result to a non-significant level (P=0.094). There were no differences between groups in the secondary outcome measures. CONCLUSIONS Patients receiving Thyroidinum had less weight reduction on day 2 after treatment than those receiving placebo. Yet, since no significant differences were found in other outcomes and since adjustment for baseline differences rendered the difference for the main outcome measure non-significant, this result must be interpreted with caution. Post hoc evaluation of the data, however, suggests that by predefining the primary outcome measure in a different way, an augmented reduction of weight on day 1 after treatment with Thyroidinum may be demonstrated. Both results would be compatible with homeopathic doctrine (primary and secondary effect) as well as with findings from animal research.
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Affiliation(s)
- J M Schmidt
- Krankenhaus für Naturheilweisen, Munich, Germany.
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Reyns GE, Janssens KA, Buyse J, Kühn ER, Darras VM. Changes in thyroid hormone levels in chicken liver during fasting and refeeding. Comp Biochem Physiol B Biochem Mol Biol 2002; 132:239-45. [PMID: 11997225 DOI: 10.1016/s1096-4959(01)00528-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In chickens, fasting results in increased plasma thyroxine (T(4)) levels and decreased plasma 3,5,3'-triiodothyronine (T(3)) levels. Refeeding, in turn, restores normal plasma T(3) and T(4) levels. The liver is an important tissue for the regulation of circulating thyroid hormone levels. Previous studies demonstrated that the increase in hepatic type III deiodinase in fasted chickens plays a role in the decrease of plasma T(3). Another factor that could be important is the level of T(4) and T(3) uptake by the liver. In mammals, caloric restriction is known to diminish transport of T(4) and T(3) into tissues. The present study examines whether this is also the case in chicken. Four-week-old chickens were subjected to a 24-h starvation period followed by refeeding. Blood and liver samples were collected at the start of refeeding and at different times of refeeding. Thyroid hormone levels were measured directly in plasma and in tissues following extraction. The results demonstrate that intrahepatic T(4) levels are increased and T(3) levels are decreased in fasted compared to ad libitum fed chickens. The parallel changes in plasma and hepatic T(3) and T(4) content demonstrate that T(4) availability in liver tissue is not diminished during fasting, suggesting that in chicken thyroid hormone uptake by the liver is not affected by nutritional status.
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Affiliation(s)
- G E Reyns
- Department of Biology, KU Leuven, Zoological Institute, Laboratory of Comparative Endocrinology, Leuven, Belgium.
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Hennemann G, Docter R, Friesema EC, de Jong M, Krenning EP, Visser TJ. Plasma membrane transport of thyroid hormones and its role in thyroid hormone metabolism and bioavailability. Endocr Rev 2001; 22:451-76. [PMID: 11493579 DOI: 10.1210/edrv.22.4.0435] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Although it was originally believed that thyroid hormones enter target cells by passive diffusion, it is now clear that cellular uptake is effected by carrier-mediated processes. Two stereospecific binding sites for each T4 and T3 have been detected in cell membranes and on intact cells from humans and other species. The apparent Michaelis-Menten values of the high-affinity, low-capacity binding sites for T4 and T3 are in the nanomolar range, whereas the apparent Michaelis- Menten values of the low-affinity, high-capacity binding sites are usually in the lower micromolar range. Cellular uptake of T4 and T3 by the high-affinity sites is energy, temperature, and often Na+ dependent and represents the translocation of thyroid hormone over the plasma membrane. Uptake by the low-affinity sites is not dependent on energy, temperature, and Na+ and represents binding of thyroid hormone to proteins associated with the plasma membrane. In rat erythrocytes and hepatocytes, T3 plasma membrane carriers have been tentatively identified as proteins with apparent molecular masses of 52 and 55 kDa. In different cells, such as rat erythrocytes, pituitary cells, astrocytes, and mouse neuroblastoma cells, uptake of T4 and T3 appears to be mediated largely by system L or T amino acid transporters. Efflux of T3 from different cell types is saturable, but saturable efflux of T4 has not yet been demonstrated. Saturable uptake of T4 and T3 in the brain occurs both via the blood-brain barrier and the choroid plexus-cerebrospinal fluid barrier. Thyroid hormone uptake in the intact rat and human liver is ATP dependent and rate limiting for subsequent iodothyronine metabolism. In starvation and nonthyroidal illness in man, T4 uptake in the liver is decreased, resulting in lowered plasma T3 production. Inhibition of liver T4 uptake in these conditions is explained by liver ATP depletion and increased concentrations of circulating inhibitors, such as 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, indoxyl sulfate, nonesterified fatty acids, and bilirubin. Recently, several organic anion transporters and L type amino acid transporters have been shown to facilitate plasma membrane transport of thyroid hormone. Future research should be directed to elucidate which of these and possible other transporters are of physiological significance, and how they are regulated at the molecular level.
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Affiliation(s)
- G Hennemann
- Department of Nuclear Medicine, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands.
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Abstract
Tissue-specific activation and inactivation of ligands of nuclear receptors which belong to the steroid retinoid-thyroid hormone superfamily of transcription factors represents an important principle of development- and tissue-specific local modulation of hormone action. Recently, several enzyme families have been identified which act as 'guardians of the gate' of ligand-activated transcription modulation. Three monodeiodinase isoenzymes which are involved in activation the 'prohormone' L-thyroxine (T4), the main secretory product of the thyroid gland, have been identified, characterized, and cloned. Both, type I and type II 5'-deiodinase generate the thyromimetically active hormone 3,3',5-triiodothyronine (T3) by reductive deiodination of the phenolic ring of T4. Inactivation of T4 and its product T3 occurs by deiodination of iodothyronines at the tyrosyl ring. This reaction is catalyzed both the type III 5-deiodinase and also by the type I enzyme, which has a broader substrate specificity. The three deiodinases appear to constitute a newly discovered family of selenocysteine-containing proteins and the presence of selenocysteine in the protein is critical for enzyme activity. Whereas the selenoenzyme characteristics of the type I and type III deiodinases are definitively established some controversy still exists for the type II 5'-deiodinase in mammals. The mRNA probably encoding the type II 5'-deiodinase subunit is markedly longer than those of the two other deiodinases and its selenocysteine-insertion element is located more than 5 kB downstream of the UGA-codon in the 3'-untranslated region. The three deiodinase isoenzymes show a distinct development- and tissue-specific pattern of expression, operate at individual optimal substrate levels, are differently regulated and modulated by hormones, cytokines, signaling pathways, natural factors, and pharmaceuticals. Whereas circulating T3 mainly originates from hepatic production via the type I 5'-deiodinase, the local cellular thyroid hormone concentration in various tissues including the central nervous system is controlled by complex para-, auto-, and intracrine interactions of all three deiodinases. Local thyroid hormone availability is further modulated by conjugation reactions of the phenolic 4'-OH-group of iodothyronines, which also inactivate the thyroid hormones.
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Affiliation(s)
- J Köhrle
- Abteilung für Molekulare Innere Medizin und Klinische Forschergruppe der Medizinischen Poliklinik der Universität Würzburg, Germany.
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Escobar-Morreale HF, Obregón MJ, Escobar del Rey F, Morreale de Escobar G. Tissue-specific patterns of changes in 3,5,3'-triiodo-L-thyronine concentrations in thyroidectomized rats infused with increasing doses of the hormone. Which are the regulatory mechanisms? Biochimie 1999; 81:453-62. [PMID: 10403175 DOI: 10.1016/s0300-9084(99)80095-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We have measured 3,5,3'triiodothyronine (T3) in 12 tissues from thyroidectomized (Tx) rats infused with increasing doses of T3, and related them to their corresponding plasma levels. Young adult Wistar rats were surgically Tx. After 4 weeks, the animals were infused with placebo or T3 (0.25, 0.50, 0.75, 1.00 or 2.00 microg/100 g body weight/day). Placebo-infused intact rats served as euthyroid controls. Plasma and samples of cerebral cortex, cerebellum, brown adipose tissue (BAT), pituitary, liver, heart, lung, kidney, spleen, skeletal muscle, ovary and adrenal were obtained after 12-13 days of infusion. We determined plasma T3 and thyrotropin (TSH), and tissue T3 and thyroxine (T4), the latter being virtually undetectable. Results were compared with the relationships between tissue and plasma T3 in Tx rats on T4 infusions. Most tissues presented changes which paralleled those in plasma T3, irrespective of its source (infusion of T3, or generation from infused T4). However, at similar plasma T3 concentrations, cerebral cortex, cerebellum and BAT (containing type II 5' iodothyronine deiodinase (DII) activity), reached much lower T3 levels in the T3-infused Tx rats, than in Tx rats on T4, and required elevated plasma T3 levels for normal tissue T3. In these tissues, and in the pituitary, T3 concentrations were always lower than expected from plasma T3 levels. On the contrary, the lung and ovary of the T3-infused Tx rats contained more T3 than expected from plasma T3. Unexpectedly, both the ovary and adrenal attained higher tissue T3 concentrations in Tx rats on T3 than on T4 at comparable plasma T3 levels. In conclusion, the patterns of changes of the concentrations of T3 as a function of increasing plasma T3 are not only tissue-specific when T4 is provided, but also when circulating T3 is the only source of this iodothyronine. Further studies are needed to identify the mechanisms involved in the regulation of tissue T3 concentrations.
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Affiliation(s)
- H F Escobar-Morreale
- Molecular Endocrinology Unit, Instituto de Investigaciones Biomédicas, CSIC & UAM, Madrid, Spain
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Reinhardt W, Mann K. [Non-thyroid illness" or changed thyroid hormone parameter syndrome with non-thyroid illnesses]. MEDIZINISCHE KLINIK (MUNICH, GERMANY : 1983) 1998; 93:662-8. [PMID: 9872043 DOI: 10.1007/bf03044878] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The multiple effects of systemic illness on thyroid economy are commonly referred to "non-thyroidal illness" (NTI) or "sick euthyroid syndrome". The various aspects of this common syndrome are summarized in this article. STUDIES Results of the relevant studies published during the past 25 years were evaluated. The influence of the underlying illness and of drug administration was especially emphasized. RESULTS The most common abnormalities in NTI are 1. the "low-T3 syndrome" due to a decreased T3 generation from T4 by a reduced activity of 5'-deiodinase (a selenoprotein); 2. the "low-T3 low-T4 state", which is associated with a poor prognosis. The low T4-levels are related to a binding inhibitor that displaces T4 from its binding proteins. However, there exists some controversy regarding the character of this binding inhibitor. 3. The high-T4 state is often found in acute psychiatric and liver diseases. The nutritional status of the patients and drugs known to influence thyroid hormone parameters have to be considered when patients with NTI are evaluated. Some difficulties may arise, when there is evidence of coexisting thyroid disease. Here aside from further biochemical evaluation such as thyroid antibodies, thyroid ultrasound and a thyroid scan have to be performed. CONCLUSION NTI is associated with various alterations in thyroid hormone parameters when no intrinsic thyroid hormone disease exists. The severity of NTI reflects clinical outcome and clinical amelioration is associated with normalization of thyroid hormone parameters. There is no need for specific therapeutic intervention such as the administration of thyroid hormones in patients with the various forms of the NTI-syndrome.
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Affiliation(s)
- W Reinhardt
- Abteilung für Endokrinologie, Zentrum für Innere Medizin, Universitätsklinikum Essen.
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24
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Abstract
INTRODUCTION Patients with nonthyroidal disease frequently exhibit abnormal thyroid function tests; this is referred to as euthyroid sick syndrome. The clinical significance of this syndrome is unknown: abnormal endocrine reaction with reduced triiodothyronine (T3) at the tissue level, or adaptation to stress protecting the body against exaggerated catabolism. CURRENT KNOWLEDGE AND KEY POINTS Recent advances in the underlying mechanisms concern the role of deiodinase and of the transport of thyroid hormone in tissues. Various factors acting on deiodinase or on transport system, such as medications and nutritional factors, have been implicated. Considerable interest has raised concerning the role of cytokines. Some cytokines may act at every level of the thyrotropic axis, but their real action in vivo remains unclear. Nutritional factors have a great impact on thyroid hormone metabolism, but the mechanism of the decrease in T3 induced by starvation is not identified. The role of the decrease in type I hepatic deiodinase has been recently challenged. FUTURE PROSPECTS AND PROJECTS Despite its complexity, euthyroid sick syndrome is a model for the study of thyroid hormone metabolism regulation. Characterisation of the thyroid hormone transport proteins will lead to significant advances in the understanding of the syndrome.
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Affiliation(s)
- B Goichot
- Service de médecine interne, hôpital de Hautepierre, Strasbourg, France
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