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Iwen KA, Schröder E, Brabant G. Thyroid hormones and the metabolic syndrome. Eur Thyroid J 2013; 2:83-92. [PMID: 24783045 PMCID: PMC3821514 DOI: 10.1159/000351249] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 04/11/2013] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Clustering of various metabolic parameters including abdominal obesity, hyperglycaemia, low high-density lipoprotein cholesterol, elevated triglycerides and hypertension have been used worldwide as metabolic syndrome to predict cardiometabolic risk. Thyroid dysfunction impacts on various levels of these components. OBJECTIVES The purpose of the present review is to summarize available data on thyroid hormone-dependent action on components of the metabolic syndrome. METHODS A PubMed search for any combination of hyperthyroidism, thyrotoxicosis or hypothyroidism and metabolic syndrome, blood pressure, hypertension, hyperlipidaemia, cholesterol, high-density lipoprotein cholesterol, glucose, diabetes mellitus, body weight or visceral fat was performed. We included papers and reviews published between 2000 and today but accepted also frequently cited papers before 2000. RESULTS There is convincing evidence for a major impact of thyroid function on all components of the metabolic syndrome, reflecting profound alterations of energy homeostasis at many levels. CONCLUSION Even though the interactions shown in animal models and man are complex, it is evident that insulin sensitivity is highest and adverse thyroid effects on the metabolic system are lowest in euthyroid conditions.
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Affiliation(s)
- K. Alexander Iwen
- Medizinische Klinik I, Experimentelle und Klinische Endokrinologie, Universität zu Lübeck, Lübeck, Germany
| | - Erich Schröder
- Medizinische Klinik I, Experimentelle und Klinische Endokrinologie, Universität zu Lübeck, Lübeck, Germany
| | - Georg Brabant
- Medizinische Klinik I, Experimentelle und Klinische Endokrinologie, Universität zu Lübeck, Lübeck, Germany
- Department of Endocrinology, The Christie Manchester Academic Health Science Centre, Manchester, UK
- *Georg Brabant, Medizinische Klinik I, Experimentelle und Klinische Endokrinologie, Universität zu Lübeck, Ratzeburger Allee 160, DE-23538 Lübeck (Germany), E-Mail
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Oguz A, Tuzun D, Ozdemir D, Baci Y, Ersoy R, Avsar AF, Cakir B. Prevalance of gestational diabetes mellitus in patients with gestational transient thyrotoxicosis. Gynecol Endocrinol 2013; 29:336-9. [PMID: 23327556 DOI: 10.3109/09513590.2012.752451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE To investigate prevalence of gestational diabetes mellitus (GDM) in patients with gestational transient thyroxicosis (GTT). METHODS Fifty two patients with GTT and 100 age matched healthy pregnant women were included. Fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), LDL-cholesterol, HDL-cholesterol, triglyceride, thyrotrophin (TSH) and thyroid hormones were measured at thyrotoxic state in GTT patients and at 6-12th weeks of pregnancy in control group. Oral glucose tolerance test (OGTT) with 100 g glucose was performed and laboratory parameters were re-evaluated at 24-28th weeks of pregnancy in all subjects. RESULTS Mean age of patients with GTT was 28.46 ± 5.45 and control group was 27.78 ± 3.75(p = 0.085). Patients with GTT had significantly higher HbA1c, LDL-cholesterol and HDL-cholesterol at 6-12th weeks of pregnancy (p < 0.01, p < 0.01 and p = 0.034, respectively). TSH was negatively correlated with HbA1c and LDL-cholesterol in thyrotoxic state in GTT patients (r = -0.393, p < 0.001 and r = -0.293, p < 0.001, respectively). OGTT showed GDM in 7 (13.5%) GTT patients and 4 (4%) healthy pregnants (p = 0.047). HbA1c, LDL-cholesterol and HDL-cholesterol were higher in GTT patients compared to healthy pregnants also at 24-28th weeks of pregnancy (p < 0.001, p < 0.001 and p = 0.024). CONCLUSION Although GTT is known to be a transient state that can resolve spontaneously, it might have negative effect on carbohydrate metabolism like other causes of hyperthyroidism.
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Affiliation(s)
- Ayten Oguz
- Department of Endocrinology and Metabolism, Ataturk Education and Research Hospital, Yıldırım Beyazit University, Ankara, Turkey
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Balbach L, Wallaschofski H, Völzke H, Nauck M, Dörr M, Haring R. Serum prolactin concentrations as risk factor of metabolic syndrome or type 2 diabetes? BMC Endocr Disord 2013; 13:12. [PMID: 23517652 PMCID: PMC3614874 DOI: 10.1186/1472-6823-13-12] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 03/15/2013] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND To investigate potential associations of serum prolactin concentration (PRL) with metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM), previously observed in small and selected study samples, in a large population-based cohort. METHODS Data from 3,993 individuals (2,027 women) aged 20-79 years from the population-based Study of Health of Pomerania (SHIP) were used to analyse cross-sectional and longitudinal associations of PRL with MetS and T2DM risk in age- and multivariable-adjusted Poisson regression models. PRL were log-transformed and modelled as continuous (per standard deviation (SD) increase) and categorical predictor (sex-specific quartiles) variable, separately for men and woman. RESULTS Cross-sectional analyses showed an inverse association between low PRL concentrations and prevalent T2DM risk in men and women after multivariable-adjustment (men: Q1 vs. Q4: relative risk (RR), 1.55; 95% confidence interval (CI), 1.13 - 2.14; women: Q1 vs. Q4: RR, 1.70; 95% CI, 1.10 - 2.62). Likewise, higher PRL concentrations were associated with significantly lower T2DM risk (RR per SD increase in log-PRL: 0.83; 95% CI, 0.72 - 0.95 in men, and 0.84; 95% CI, 0.71 - 0.98 in women, respectively). An inverse association between PRL and MetS risk was not retained after multivariable adjustment. Longitudinal analyses yielded no association of PRL with incident MetS or T2DM. CONCLUSION The present study is the first large population-based study reporting a cross-sectional inverse association between PRL and prevalent T2DM in both genders. But the absent longitudinal associations do not support a causal role of PRL as a risk factor of incident MetS or T2DM.
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Affiliation(s)
- Lisa Balbach
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, Greifswald, 17475, Germany
| | - Henri Wallaschofski
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, Greifswald, 17475, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
| | - Henry Völzke
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
- Institute for Community Medicine, University Medicine Greifswald, Walther-Rathenau-Straße 48, Greifswald, 17475, Germany
| | - Matthias Nauck
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, Greifswald, 17475, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
| | - Marcus Dörr
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
- Department of Cardiology, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, Greifswald, 17475, Germany
| | - Robin Haring
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, Greifswald, 17475, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
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Schmid SM, Hallschmid M, Jauch-Chara K, Kück MC, Lehnert H, Schultes B. Partial sleep restriction modulates secretory activity of thyrotropic axis in healthy men. J Sleep Res 2013; 22:166-9. [PMID: 23495953 DOI: 10.1111/jsr.12004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 09/24/2012] [Indexed: 01/09/2023]
Abstract
Sleep and endocrine function are known to be closely related, but studies on the effect of moderate sleep loss on endocrine axes are still sparse. We examined the influence of partial sleep restriction for 2 days on the secretory activity of the thyrotropic axis. Fifteen healthy, normal-weight men were tested in a balanced, cross-over study. Serum concentrations of thyrotrophin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) were monitored at 1-h intervals during a 15-h daytime period (08:00-23:00 h) following two nights of restricted sleep (bedtime 02:45-07:00 h) and two nights of regular sleep (bedtime 22:45-07:00 h), respectively. Serum concentrations of fT3 (P < 0.026) and fT4 (P = 0.089) were higher after sleep restriction than regular sleep, with a subsequent blunting of TSH concentrations in the evening hours of the sleep restriction condition (P = 0.008). These results indicate profound alterations in the secretory activity of the thyrotropic axis after 2 days of sleep restriction to ~4 h, suggesting that acute partial sleep loss impacts endocrine homeostasis, with potential consequences for health and wellbeing.
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Affiliation(s)
- Sebastian M Schmid
- Department of Internal Medicine I, University of Luebeck, Luebeck, Germany.
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Wang C. The Relationship between Type 2 Diabetes Mellitus and Related Thyroid Diseases. J Diabetes Res 2013; 2013:390534. [PMID: 23671867 PMCID: PMC3647563 DOI: 10.1155/2013/390534] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 03/15/2013] [Indexed: 12/12/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) has an intersecting underlying pathology with thyroid dysfunction. The literature is punctuated with evidence indicating a contribution of abnormalities of thyroid hormones to type 2 DM. The most probable mechanism leading to T2DM in thyroid dysfunction could be attributed to perturbed genetic expression of a constellation of genes along with physiological aberrations leading to impaired glucose utilization and disposal in muscles, overproduction of hepatic glucose output, and enhanced absorption of splanchnic glucose. These factors contribute to insulin resistance. Insulin resistance is also associated with thyroid dysfunction. Hyper- and hypothyroidism have been associated with insulin resistance which has been reported to be the major cause of impaired glucose metabolism in T2DM. The state-of-art evidence suggests a pivotal role of insulin resistance in underlining the relation between T2DM and thyroid dysfunction. A plethora of preclinical, molecular, and clinical studies have evidenced an undeniable role of thyroid malfunctioning as a comorbid disorder of T2DM. It has been investigated that specifically designed thyroid hormone analogues can be looked upon as the potential therapeutic strategies to alleviate diabetes, obesity, and atherosclerosis. These molecules are in final stages of preclinical and clinical evaluation and may pave the way to unveil a distinct class of drugs to treat metabolic disorders.
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Affiliation(s)
- Chaoxun Wang
- Department of Endocrinology, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Huinan Town, Pudong, Shanghai 201399, China
- *Chaoxun Wang:
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56
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Moura Neto A, Parisi MCR, Tambascia MA, Alegre SM, Pavin EJ, Zantut-Wittmann DE. The influence of body mass index and low-grade systemic inflammation on thyroid hormone abnormalities in patients with type 2 diabetes. Endocr J 2013; 60:877-84. [PMID: 23558976 DOI: 10.1507/endocrj.ej13-0030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Previous reports highlight the role of systemic inflammation in the genesis of non-thyroidal illness syndrome and type 2 diabetes mellitus (T2DM). Our objective was to assess whether body mass index and the low-grade systemic inflammation would be associated with changes in thyroid hormone metabolism in patients with type 2 diabetes. This was a cross-sectional study of 104 subjects; 52 patients with type 2 diabetes and 52 in a control group, paired by age, gender and body mass index. We measured total (T) and free (F) thyroxine (T4) and triiodothyronine (T3), reverse T3 (rT3), the ratios FT3/rT3, FT3/FT4 and FT4/rT3, clinical parameters (age, gender, diabetes duration and complications, body mass index, waist circumference, hypertension, HbA1c), and high sensitivity C-reactive protein. Patients with DM presented lower levels of TT4 (p=0.006), TT3 (p<0.001) and FT3 (p<0.001) and higher of FT4 (p<0.001), waist circumference (p=0.047) and C-reactive protein (p<0.001). Body mass index was inversely correlated with FT4 (p=0.036) and TT3 (p=0.008). C-reactive protein was positively correlated with rT3 (p=0.001) and inversely with FT4/rT3 (p<0.001) and FT3/rT3 (p=0.014). Body mass index was an independent predictor for FT4 (B=-0.011, p=0.029) and TT3 levels (B=-1.118, p=0.003). Inflammation predicted the FT4/rT3 ratio (B=-0.190, p<0.001). C-reactive protein (B=0.235, p<0.001) and body mass index (B=-0.008, p=0.047) were independent predictors for rT3. In conclusion, type 2 diabetes was associated with a low T3 state. Body mass index and the low-grade systemic inflammation are related to the non-thyroidal illness syndrome in these patients, possibly by altering the activity of peripheral deiodinases.
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Affiliation(s)
- Arnaldo Moura Neto
- Endocrinology Division, Clinical Medicine Department, Faculty of Medical Sciences, University of Campinas, Campinas, Brazil
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57
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Gebauer J, Schuster S, de Figueiredo LF, Kaleta C. Detecting and investigating substrate cycles in a genome-scale human metabolic network. FEBS J 2012; 279:3192-202. [PMID: 22776428 DOI: 10.1111/j.1742-4658.2012.08700.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Substrate cycles, also known as futile cycles, are cyclic metabolic routes that dissipate energy by hydrolysing cofactors such as ATP. They were first described to occur in the muscles of bumblebees and brown adipose tissue in the 1970s. A popular example is the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate and back. In the present study, we analyze a large number of substrate cycles in human metabolism that consume ATP and discuss their statistics. For this purpose, we use two recently published methods (i.e. EFMEvolver and the K-shortest EFM method) to calculate samples of 100,000 and 15,000 substrate cycles, respectively. We find an unexpectedly high number of substrate cycles in human metabolism, with up to 100 reactions per cycle, utilizing reactions from up to six different compartments. An analysis of tissue-specific models of liver and brain metabolism shows that there is selective pressure that acts against the uncontrolled dissipation of energy by avoiding the coexpression of enzymes belonging to the same substrate cycle. This selective force is particularly strong against futile cycles that have a high flux as a result of thermodynamic principles.
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Affiliation(s)
- Juliane Gebauer
- Department of Bioinformatics, School of Biology and Pharmaceutics and JenAge Research Core, Friedrich Schiller University of Jena, Germany
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58
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Ribeiro LFP, Teixeira IP, Aparecido da Silva G, Dalia RA, Júnior MC, Bertolini NO, Rostom de Mello MA, Luciano E. Effects of swimming training on tissue glycogen content in experimental thyrotoxic rats. Can J Physiol Pharmacol 2012; 90:587-93. [DOI: 10.1139/y2012-044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Thyrotoxicosis, a condition in which there is an excessive amount of circulating thyroid hormones, leads to reduced glycogen content in different tissues. In this study we analyzed the effects of aerobic swimming training on liver, heart, and skeletal muscle glycogen content in experimentally induced thyrotoxicosis. Wistar male rats were divided into euthyroid sedentary (ES, n = 12), euthyroid trained (ET, n = 11), thyrotoxic sedentary (TS, n = 12), and thyrotoxic trained (TT, n = 10) groups. Thyrotoxic groups received daily i.p. doses of T4 (sodium levothyroxine, 25 µg/100 g body mass) through the experimental period, and trained groups swam for 1 h at 80% of the aerobic–anaerobic transition intensity, 5 days/week for 4 weeks. Heart and liver glycogen stores were ∼30% lower in T4 treated compared with nontreated groups, but were not changed by training status. On the other hand, glycogen content in mixed fiber type gastrocnemius of TT was 1.5- to 2.3-fold greater than those in other groups, whereas no significant differences were found for the slow soleus muscle. Increased gastrocnemius but not soleus, liver, or heart glycogen indicates that in mild long-term thyrotoxicosis chronic swimming affects glycogen stores in a tissue-specific manner.
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Affiliation(s)
- Luiz Fernando Paulino Ribeiro
- Departamento de Ciências da Saúde, Universidade Estadual de Santa Cruz, Ilhéus-Itabuna, Bahia 45662-900, Brazil
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Inaian Pignatti Teixeira
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Glaucio Aparecido da Silva
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Rodrigo Augusto Dalia
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Marcelo Costa Júnior
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Natalia Oliveira Bertolini
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Maria Alice Rostom de Mello
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
| | - Eliete Luciano
- Departamento de Educação Física, Instituto de Biociências, Universidade Estadual Paulista, Avenida 24A, No. 1515, Bela Vista, Rio Claro, São Paulo 13506-900, Brazil
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Amory JK, Hirsch IB. Hyperthyroidism from autoimmune thyroiditis in a man with type 1 diabetes mellitus: a case report. J Med Case Rep 2011; 5:277. [PMID: 21722403 PMCID: PMC3141718 DOI: 10.1186/1752-1947-5-277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Accepted: 07/03/2011] [Indexed: 11/17/2022] Open
Abstract
Introduction The presentation, diagnosis, clinical course and treatment of a man with hyperthyroidism secondary to autoimmune thyroiditis in the setting of type 1 diabetes mellitus has not previously been described. Case presentation A 32-year-old European-American man with an eight-year history of type 1 diabetes mellitus presented with an unintentional 22-pound weight loss but an otherwise normal physical examination. Laboratory studies revealed a suppressed thyroid-stimulating hormone concentration and an elevated thyroxine level, which are consistent with hyperthyroidism. His anti-thyroid peroxidase antibodies were positive, and his thyroid-stimulating immunoglobulin test was negative. Uptake of radioactive iodine by scanning was 0.5% at 24 hours. The patient was diagnosed with autoimmune thyroiditis. Six weeks following his initial presentation he became clinically and biochemically hypothyroid and was treated with thyroxine. Conclusion This report demonstrates that autoimmune thyroiditis presenting as hyperthyroidism can occur in a man with type 1 diabetes mellitus. Autoimmune thyroiditis may be an isolated manifestation of autoimmunity or may be part of an autoimmune polyglandular syndrome. Among patients with type 1 diabetes mellitus who present with hyperthyroidism, Graves' disease and other forms of hyperthyroidism need to be excluded as autoimmune thyroiditis can progress quickly to hypothyroidism, requiring thyroid hormone replacement therapy.
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Affiliation(s)
- John K Amory
- Division of General Internal Medicine, Department of Medicine, University of Washington School of Medicine, 1959 NE Pacific Street, Seattle, WA 98195, USA.
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60
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Abstract
Thyroid disease and type 1 but also type 2 diabetes mellitus (DM) are strongly associated, and this has important clinical implications for insulin sensitivity and treatment requirements. The pathophysiological basis of this association has only recently been better elucidated. It rests on a complex interaction of common signalling pathways and, in the case of type 1 diabetes and autoimmune thyroid disease, on a linked genetic susceptibility. The pathophysiological mechanisms underlying this linked regulation are increasingly being unravelled. They are exemplified in the regulation of 5' adenosine monophosphate-activated protein kinase (AMPK), a central target not only for the modulation of insulin sensitivity but also for the feedback of thyroid hormones on appetite and energy expenditure. The present review will discuss these concepts and their consequences for the clinical care of patients with DM and thyroid disorders. Moreover, it makes reference to the added effect of metformin in suppressing TSH.
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Affiliation(s)
- Leonidas H Duntas
- Endocrine Unit, Evgenidion Hospital, University of Athens Medical School, Athens, GreeceService d' Endocrinologie-Diabète-Maladies Métaboliques, Centre Hospitalier, Lyon-Sud, FranceDepartment of Endocrinology, The Christie, Manchester Academic Health Science Centre, Manchester, UK
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Atherton HJ, Dodd MS, Heather LC, Schroeder MA, Griffin JL, Radda GK, Clarke K, Tyler DJ. Role of pyruvate dehydrogenase inhibition in the development of hypertrophy in the hyperthyroid rat heart: a combined magnetic resonance imaging and hyperpolarized magnetic resonance spectroscopy study. Circulation 2011; 123:2552-61. [PMID: 21606392 DOI: 10.1161/circulationaha.110.011387] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND Hyperthyroidism increases heart rate, contractility, cardiac output, and metabolic rate. It is also accompanied by alterations in the regulation of cardiac substrate use. Specifically, hyperthyroidism increases the ex vivo activity of pyruvate dehydrogenase kinase, thereby inhibiting glucose oxidation via pyruvate dehydrogenase. Cardiac hypertrophy is another effect of hyperthyroidism, with an increase in the abundance of mitochondria. Although the hypertrophy is initially beneficial, it can eventually lead to heart failure. The aim of this study was to use hyperpolarized magnetic resonance spectroscopy to investigate the rate and regulation of in vivo pyruvate dehydrogenase flux in the hyperthyroid heart and to establish whether modulation of flux through pyruvate dehydrogenase would alter cardiac hypertrophy. METHODS AND RESULTS Hyperthyroidism was induced in 18 male Wistar rats with 7 daily intraperitoneal injections of freshly prepared triiodothyronine (0.2 mg x kg(-1) x d(-1)). In vivo pyruvate dehydrogenase flux, assessed with hyperpolarized magnetic resonance spectroscopy, was reduced by 59% in hyperthyroid animals (0.0022 ± 0.0002 versus 0.0055 ± 0.0005 second(-1); P=0.0003), and this reduction was completely reversed by both short- and long-term delivery of dichloroacetic acid, a pyruvate dehydrogenase kinase inhibitor. Hyperpolarized [2-(13)C]pyruvate was also used to evaluate Krebs cycle metabolism and demonstrated a unique marker of anaplerosis, the level of which was significantly increased in the hyperthyroid heart. Cine magnetic resonance imaging showed that long-term dichloroacetic acid treatment significantly reduced the hypertrophy observed in hyperthyroid animals (100 ± 20 versus 200 ± 30 mg; P=0.04) despite no change in the increase observed in cardiac output. CONCLUSIONS This work has demonstrated that inhibition of glucose oxidation in the hyperthyroid heart in vivo is mediated by pyruvate dehydrogenase kinase. Relieving this inhibition can increase the metabolic flexibility of the hyperthyroid heart and reduce the level of hypertrophy that develops while maintaining the increased cardiac output required to meet the higher systemic metabolic demand.
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Affiliation(s)
- Helen J Atherton
- Department of Biochemistry, Sanger Bldg, University of Cambridge, Tennis Court Rd, Cambridge CB2 1GA, UK.
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Wintergerst KA, Rogers ES, Foster MB. Hyperthyroidism presenting with hyperglycemia in an adolescent female. J Pediatr Endocrinol Metab 2011; 24:385-7. [PMID: 21823542 DOI: 10.1515/jpem.2011.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A 15-year-old female presented to a pediatric emergency department with glycosuria, ketonuria, and hyperglycemia and was admitted with a presumed diagnosis of diabetes mellitus. The patient required no insulin therapy and only minor dietary modification to maintain euglycemia. Clinical examination and laboratory findings revealed a primary diagnosis of Graves' hyperthyroidism with associated impaired glucose tolerance. Here, we review the mechanisms of thyrotoxicosis resulting in impaired glucose metabolism.
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Affiliation(s)
- Kupper A Wintergerst
- Division of Endocrinology, Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA.
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