Transthyretin as a Thyroid Hormone Carrier: Function Revisited
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Joana Almeida Palha
Abstract
Thyroid hormones are essential for normal mammalian development and for normal metabolism. Thyroxine (T4) is the principal product synthesized by the thyroid follicles, and triiodothyronine (T3), the biologically active hormone, derives mainly from tissue T4 deiodination. More than 99% of the circulating hormone is bound to plasma proteins, mainly to thyroxine-binding globulin, transthyretin and albumin in man, and to transthyretin and albumin in rodents. The role of plasma proteins in the transport of hormones to target tissues has, for a long time, been controversial. The liver and the choroid plexus are the major sites of transthyretin synthesis, tissues from which transthyretin is secreted into the blood and the cerebrospinal fluid, respectively. Transthyretin has been proposed to mediate thyroid hormone transfer into the tissues, particularly into the brain across the choroid-plexus-cerebrospinal fluid barrier. Studies in a transthyretinnull mice strain have shown conclusively that transthyretin is not indespensable for thyroid hormones' entry into the brain and other tissues, nor for the maintenance of an euthyroid status. An euthyroid status is also observed in man totally deprived of thyroxine-binding globulin and in rats without albumin. Taken together, these results exclude dependence of thyroid hormone homeostasis on any major plasma carrier per se. This evidence agrees with the free hormone hypothesis which states that the biologically significant fraction, that is taken up by the tissues, is the free circulating hormone.
Copyright © 2002 by Walter de Gruyter GmbH & Co. KG
Articles in the same Issue
- Author Index
- Subject Index
- Contents
- Historical Aspects and Perspectives in Transthyretin Research
- Transthyretin from Discovery to Now
- The Evolution of Transthyretin Synthesis in Vertebrate Liver, in Primitive Eukaryotes and in Bacteria
- The Evolution of Transthyretin Synthesis in the Choroid Plexus
- Hepatic Synthesis, Maturation and Complex Formation between Retinol-Binding Protein and Transthyretin
- Synthesis and Structural Analysis of the N-Terminal Domain of the Thyroid Hormone-Binding Protein Transthyretin
- Three-Dimensional Structure of the Transthyretin-Retinol-Binding Protein Complex
- Mechanisms of Molecular Recognition: Crystal Structure Analysis of Human and Rat Transthyretin Inhibitor Complexes
- Transthyretin in Fish: State of the Art
- The Effects of Endocrine-Disrupting Chemicals on Thyroid Hormone Binding to Xenopus laevis Transthyretin and Thyroid Hormone Receptor
- Clinical Picture and Outcome of Transthyretin-Related Familial Amyloid Polyneuropathy (FAP) in Japanese Patients
- Laboratory Assessment of Transthyretin Amyloidosis
- Amyloid: Morphology and Toxicity
- Historical Overview of Analytical Methods for the Measurement of Transthyretin
- Nutritional Regulation of Visceral Markers in Rat Liver and Cultured Hepatoma Cells
- Significance of Transthyretin in Protein Metabolism
- Transthyretin as a Thyroid Hormone Carrier: Function Revisited
- The Molar Ratio of Retinol-Binding Protein to Transthyretin in the Assessment of Vitamin A Status in Adults. Proposal of a Cut-off Point
- Observations with Regard to the National Kidney Foundation K/DOQI Clinical Practice Guidelines Concerning Serum Transthyretin in Chronic Renal Failure
- Metabolism and Clinical Interest of Serum Transthyretin (Prealbumin) in Dialysis Patients
- Protein Status in Pancreatitis – Transthyretin Is a Sensitive Biomarker of Malnutrition in Acute and Chronic Pancreatitis
- Assessment of Nutritional Status in Organ Transplant: Is Transthyretin a Reliable Indicator?
- Body Composition and Nutritional Parameters in HIV and AIDS Patients
- C-Reactive Protein to Transthyretin Ratio for the Early Diagnosis and Follow-up of Postoperative Infection
- The Prognostic Value of Nutritional and Inflammatory Indices in Critically Ill Patients with Acute Respiratory Failure
- Transthyretin: Its Response to Malnutrition and Stress Injury. Clinical Usefulness and Economic Implications
- Transthyretin Measurement as a Screening Tool for Protein Calorie Malnutrition in Emergency Hospital Admissions
- Outcomes of Continuous Process Improvement of a Nutritional Care Program Incorporating TTR Measurement
- The Role of Visceral Protein Markers in Protein Calorie Malnutrition
- Acknowledgement
- Meetings
Articles in the same Issue
- Author Index
- Subject Index
- Contents
- Historical Aspects and Perspectives in Transthyretin Research
- Transthyretin from Discovery to Now
- The Evolution of Transthyretin Synthesis in Vertebrate Liver, in Primitive Eukaryotes and in Bacteria
- The Evolution of Transthyretin Synthesis in the Choroid Plexus
- Hepatic Synthesis, Maturation and Complex Formation between Retinol-Binding Protein and Transthyretin
- Synthesis and Structural Analysis of the N-Terminal Domain of the Thyroid Hormone-Binding Protein Transthyretin
- Three-Dimensional Structure of the Transthyretin-Retinol-Binding Protein Complex
- Mechanisms of Molecular Recognition: Crystal Structure Analysis of Human and Rat Transthyretin Inhibitor Complexes
- Transthyretin in Fish: State of the Art
- The Effects of Endocrine-Disrupting Chemicals on Thyroid Hormone Binding to Xenopus laevis Transthyretin and Thyroid Hormone Receptor
- Clinical Picture and Outcome of Transthyretin-Related Familial Amyloid Polyneuropathy (FAP) in Japanese Patients
- Laboratory Assessment of Transthyretin Amyloidosis
- Amyloid: Morphology and Toxicity
- Historical Overview of Analytical Methods for the Measurement of Transthyretin
- Nutritional Regulation of Visceral Markers in Rat Liver and Cultured Hepatoma Cells
- Significance of Transthyretin in Protein Metabolism
- Transthyretin as a Thyroid Hormone Carrier: Function Revisited
- The Molar Ratio of Retinol-Binding Protein to Transthyretin in the Assessment of Vitamin A Status in Adults. Proposal of a Cut-off Point
- Observations with Regard to the National Kidney Foundation K/DOQI Clinical Practice Guidelines Concerning Serum Transthyretin in Chronic Renal Failure
- Metabolism and Clinical Interest of Serum Transthyretin (Prealbumin) in Dialysis Patients
- Protein Status in Pancreatitis – Transthyretin Is a Sensitive Biomarker of Malnutrition in Acute and Chronic Pancreatitis
- Assessment of Nutritional Status in Organ Transplant: Is Transthyretin a Reliable Indicator?
- Body Composition and Nutritional Parameters in HIV and AIDS Patients
- C-Reactive Protein to Transthyretin Ratio for the Early Diagnosis and Follow-up of Postoperative Infection
- The Prognostic Value of Nutritional and Inflammatory Indices in Critically Ill Patients with Acute Respiratory Failure
- Transthyretin: Its Response to Malnutrition and Stress Injury. Clinical Usefulness and Economic Implications
- Transthyretin Measurement as a Screening Tool for Protein Calorie Malnutrition in Emergency Hospital Admissions
- Outcomes of Continuous Process Improvement of a Nutritional Care Program Incorporating TTR Measurement
- The Role of Visceral Protein Markers in Protein Calorie Malnutrition
- Acknowledgement
- Meetings
