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Fitzgerald SP, Falhammar H. Redefinition of Successful Treatment of Patients With Hypothyroidism. Is TSH the Best Biomarker of Euthyroidism? Front Endocrinol (Lausanne) 2022; 13:920854. [PMID: 35784560 PMCID: PMC9243528 DOI: 10.3389/fendo.2022.920854] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 05/10/2022] [Indexed: 12/14/2022] Open
Abstract
In recent years evidence has accumulated supporting a revised view of the nature of euthyroidism and the biomarkers of thyroid function. Within the normal range, variations in thyroid hormone levels are associated with variations in clinical parameters and outcomes. There are therefore no readily identified individually specific optimum levels of thyroid hormones for any individual. Levels around the middle of the normal population range may best reflect euthyroidism. These levels may have evolutionary advantages on the basis that adverse outcomes often increase with divergence from such levels, and physiological processes tend to minimise such inter-individual and intra-individual divergence. In populations of predominantly untreated individuals, levels of thyroid hormones and in particular levels of free thyroxine (FT4) correlate more often with clinical parameters than do levels of thyrotropin (TSH). Levels of thyroid hormones may therefore be regarded as the best available biomarkers of euthyroidism and dysthyroidism. It follows that 'subclinical hypothyroidism' (normal FT4/raised TSH levels), rather than being an accurate marker of peripheral tissue hypothyroidism is more a marker of decreased thyroid reserve and prognosis. The recent evidence suggests that treatment of hypothyroxinemia, regardless of the TSH level, and monitoring therapy using FT4 and/or triiodothyronine levels, depending on the replacement regime, may result in more successful treatment of hypothyroidism than relying on thyrotropin levels for patient selection and subsequent treatment monitoring. The equivalents of mid-range levels of thyroid hormones (especially FT4), adjusted by individual comorbidity concerns, may be rational general replacement targets. These implications of the new evidence may create opportunities for novel trials of thyroid replacement therapy.
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Affiliation(s)
- Stephen P. Fitzgerald
- The Departments of General Medicine and Endocrinology, The Royal Adelaide Hospital, Adelaide, SA, Australia
- School of Medicine, The University of Adelaide, Adelaide, SA, Australia
| | - Henrik Falhammar
- Department of Endocrinology, Karolinska University Hospital, Stockholm, Sweden
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
- Menzies School of Health Research and Royal Darwin Hospital, Tiwi, NT, Australia
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Samson F, He W, Sripathi SR, Patrick AT, Madu J, Chung H, Frost MC, Jee D, Gutsaeva DR, Jahng WJ. Dual Switch Mechanism of Erythropoietin as an Antiapoptotic and Pro-Angiogenic Determinant in the Retina. ACS OMEGA 2020; 5:21113-21126. [PMID: 32875248 PMCID: PMC7450639 DOI: 10.1021/acsomega.0c02763] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 07/28/2020] [Indexed: 05/07/2023]
Abstract
Constant or intense light degenerates the retina and retinal pigment epithelial cells. Light generates reactive oxygen species and nitric oxide leading to initial reactions of retinal degeneration. Apoptosis is the primary mechanism of abnormal death of photoreceptors, retinal ganglion cells, or retinal pigment epithelium (RPE) in degenerative retinal diseases, including diabetic retinopathy and age-related macular degeneration. The current study evaluated the function of erythropoietin (EPO) on angiogenesis and apoptosis in the retina and RPE under oxidative stress. We determined the pro-angiogenic and antiapoptotic mechanism of EPO under stress conditions using a conditional EPO knockdown model using siRNA, EPO addition, proteomics, immunocytochemistry, and bioinformatic analysis. Our studies verified that EPO protected retinal cells from light-, hypoxia-, hyperoxia-, and hydrogen peroxide-induced apoptosis through caspase inhibition, whereas up-regulated angiogenic reactions through vascular endothelial growth factor (VEGF) and angiotensin pathway. We demonstrated that the EPO expression in the retina and subsequent serine/threonine/tyrosine kinase phosphorylations might be linked to oxidative stress response tightly to determining angiogenesis and apoptosis. Neuroprotective roles of EPO may involve the balance between antiapoptotic and pro-angiogenic signaling molecules, including BCL-xL, c-FOS, caspase-3, nitric oxide, angiotensin, and VEGF receptor. Our data indicate a new therapeutic application of EPO toward retinal degeneration based on the dual roles in apoptosis and angiogenesis at the molecular level under oxidative stress.
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Affiliation(s)
| | - Weilue He
- Department
of Biomedical Engineering, Michigan Technological
University, Houghton 49931, United States
| | - Srinivas R. Sripathi
- Department
of Ophthalmology, Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Ambrose Teru Patrick
- Department
of Petroleum Chemistry, American University
of Nigeria, Yola 640101, Nigeria
| | - Joshua Madu
- Department
of Petroleum Chemistry, American University
of Nigeria, Yola 640101, Nigeria
| | - Hyewon Chung
- Department
of Ophthalmology, School of Medicine, Konkuk
University, Seoul 05030, Korea
| | - Megan C. Frost
- Department
of Biomedical Engineering, Michigan Technological
University, Houghton 49931, United States
| | - Donghyun Jee
- Division
of Vitreous and Retina, Department of Ophthalmology, St. Vincent’s
Hospital, College of Medicine, The Catholic
University of Korea, Suwon 16247, Korea
| | - Diana R. Gutsaeva
- Department
of Ophthalmology, Augusta University, Augusta, Georgia 30912, United States
| | - Wan Jin Jahng
- Department
of Petroleum Chemistry, American University
of Nigeria, Yola 640101, Nigeria
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Fitzgerald SP, Grote Beverborg N, Beguin Y, Artunc F, Falhammar H, Bean NG. Population data provide evidence against the presence of a set point for hemoglobin levels or tissue oxygen delivery. Physiol Rep 2019; 7:e14153. [PMID: 31243891 PMCID: PMC6594924 DOI: 10.14814/phy2.14153] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/25/2019] [Accepted: 05/27/2019] [Indexed: 01/25/2023] Open
Abstract
Hemoglobin levels are believed to be regulated as per a set point model of regulation. This model of regulation, by which specific levels of a parameter are targeted and defended by physiological systems, implies a particular population correlation between the parameter and its controlling hormone. Empirical population correlations of other parameters and their controlling hormones, have denied the presence of such set point-based regulation. To assess if hemoglobin is regulated according to a set point model we performed a systematic search of PubMed/MEDLINE and Web of Science identifying relevant reports published up to November 2018. Population hemoglobin/erythropoietin level correlations were retrieved, and these empirically derived correlations were compared with the positive correlation implied by a set point model of regulation. Authors of papers containing potentially suitable data were contacted with requests for further analyses, and a meta-analysis was performed. Twelve correlations between hemoglobin and erythropoietin levels from eleven papers were analyzed. None of these correlations were significantly positive, three, restricted to the normal range of hemoglobin, were significantly negative. All but one of the other correlations showed a negative trend. New analyses of previously published data sets resulted in similar findings. In particular a new analysis of large data sets of males (n = 2417) and females (n = 2592) with normal range hemoglobin levels, revealed significantly negative correlations. A meta-analysis of our results indicated that the data overall are not consistent with a positive relationship between hemoglobin and erythropoietin (P < 0.0001). Population data indicate that individuals do not have set point levels of hemoglobin.
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Affiliation(s)
- Stephen P. Fitzgerald
- Departments of General Medicine and EndocrinologyRoyal Adelaide HospitalAdelaideSouth AustraliaAustralia
| | - Niels Grote Beverborg
- Department of Cell and Molecular BiologyKarolinska InstitutetStockholmSweden
- Department of Medicine‐CardiologyKarolinska InstitutetStockholmSweden
- Department of CardiologyUniversity Medical Center Groningen and Rijksuniversiteit GroningenGroningenThe Netherlands
| | - Yves Beguin
- Department of HaematologyCHU de Liège and University of LiègeLiègeBelgium
| | - Ferruh Artunc
- Department of Internal MedicineDivision of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical ChemistryUniversity Hospital TübingenTübingenGermany
| | - Henrik Falhammar
- Department of Endocrinology, Metabolism and DiabetesKarolinska University HospitalStockholmSweden
- Department of Molecular Medicine and SurgeryKarolinska InstitutetStockholmSweden
- Menzies School of Health Research and Royal Darwin HospitalTiwiNorthern TerritoryAustralia
| | - Nigel G. Bean
- School of Mathematical Sciences and ARC Centre of Excellence for Mathematical and Statistical FrontiersUniversity of AdelaideAdelaideSouth AustraliaAustralia
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