Go to JCI Insight
  • About
  • Editors
  • Consulting Editors
  • For authors
  • Publication ethics
  • Alerts
  • Advertising
  • Job board
  • Subscribe
  • Contact
  • Current issue
  • Past issues
  • By specialty
    • COVID-19
    • Cardiology
    • Gastroenterology
    • Immunology
    • Metabolism
    • Nephrology
    • Neuroscience
    • Oncology
    • Pulmonology
    • Vascular biology
    • All ...
  • Videos
    • Conversations with Giants in Medicine
    • Author's Takes
  • Reviews
    • View all reviews ...
    • New Therapeutic Targets in Cardiovascular Diseases (Upcoming)
    • Immunometabolism (Jan 2022)
    • Circadian Rhythm (Oct 2021)
    • Gut-Brain Axis (Jul 2021)
    • Tumor Microenvironment (Mar 2021)
    • 100th Anniversary of Insulin's Discovery (Jan 2021)
    • Hypoxia-inducible factors in disease pathophysiology and therapeutics (Oct 2020)
    • View all review series ...
  • Viewpoint
  • Collections
    • In-Press Preview
    • Commentaries
    • Concise Communication
    • Editorials
    • Viewpoint
    • Top read articles
  • Clinical Medicine
  • JCI This Month
    • Current issue
    • Past issues

  • Current issue
  • Past issues
  • Specialties
  • Reviews
  • Review series
  • Conversations with Giants in Medicine
  • Author's Takes
  • In-Press Preview
  • Commentaries
  • Concise Communication
  • Editorials
  • Viewpoint
  • Top read articles
  • About
  • Editors
  • Consulting Editors
  • For authors
  • Publication ethics
  • Alerts
  • Advertising
  • Job board
  • Subscribe
  • Contact
Top
  • View PDF
  • Download citation information
  • Send a comment
  • Share this article
  • Terms of use
  • Standard abbreviations
  • Need help? Email the journal
  • Top
  • Abstract
  • Version history
  • Article usage
  • Citations to this article

Advertisement

Research Article Free access | 10.1172/JCI107265

Effects of Replacement Doses of Sodium-L-Thyroxine on the Peripheral Metabolism of Thyroxine and Triiodothyronine in Man

Lewis E. Braverman, Apostolos Vagenakis, Patricia Downs, Angela E. Foster, Kenneth Sterling, and Sidney H. Ingbar

St. Elizabeth's Hospital, Boston 02135

Department of Medicine, Tufts Medical School, Boston 02111

Thorndike Memorial Laboratory and the Harvard Medical Service, Boston 02115

Boston City Hospital, Boston 02118

Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

Protein Research Laboratory, Bronx Veterans Administration Hospital, Bronx, New York 10468

Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10027

Find articles by Braverman, L. in: JCI | PubMed | Google Scholar

St. Elizabeth's Hospital, Boston 02135

Department of Medicine, Tufts Medical School, Boston 02111

Thorndike Memorial Laboratory and the Harvard Medical Service, Boston 02115

Boston City Hospital, Boston 02118

Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

Protein Research Laboratory, Bronx Veterans Administration Hospital, Bronx, New York 10468

Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10027

Find articles by Vagenakis, A. in: JCI | PubMed | Google Scholar

St. Elizabeth's Hospital, Boston 02135

Department of Medicine, Tufts Medical School, Boston 02111

Thorndike Memorial Laboratory and the Harvard Medical Service, Boston 02115

Boston City Hospital, Boston 02118

Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

Protein Research Laboratory, Bronx Veterans Administration Hospital, Bronx, New York 10468

Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10027

Find articles by Downs, P. in: JCI | PubMed | Google Scholar

St. Elizabeth's Hospital, Boston 02135

Department of Medicine, Tufts Medical School, Boston 02111

Thorndike Memorial Laboratory and the Harvard Medical Service, Boston 02115

Boston City Hospital, Boston 02118

Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

Protein Research Laboratory, Bronx Veterans Administration Hospital, Bronx, New York 10468

Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10027

Find articles by Foster, A. in: JCI | PubMed | Google Scholar

St. Elizabeth's Hospital, Boston 02135

Department of Medicine, Tufts Medical School, Boston 02111

Thorndike Memorial Laboratory and the Harvard Medical Service, Boston 02115

Boston City Hospital, Boston 02118

Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

Protein Research Laboratory, Bronx Veterans Administration Hospital, Bronx, New York 10468

Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10027

Find articles by Sterling, K. in: JCI | PubMed | Google Scholar

St. Elizabeth's Hospital, Boston 02135

Department of Medicine, Tufts Medical School, Boston 02111

Thorndike Memorial Laboratory and the Harvard Medical Service, Boston 02115

Boston City Hospital, Boston 02118

Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115

Protein Research Laboratory, Bronx Veterans Administration Hospital, Bronx, New York 10468

Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10027

Find articles by Ingbar, S. in: JCI | PubMed | Google Scholar

Published May 1, 1973 - More info

Published in Volume 52, Issue 5 on May 1, 1973
J Clin Invest. 1973;52(5):1010–1017. https://doi.org/10.1172/JCI107265.
© 1973 The American Society for Clinical Investigation
Published May 1, 1973 - Version history
View PDF
Abstract

Studies of the effect of L-thyroxine administration (0.3 mg daily for 7-9 wk) on the peripheral metabolism of 131I-labeled triiodothyronine (T3) and 125I-labeled thyroxine (T4) and on the concentration and binding of T4 and T3 in serum were carried out in 11 euthyroid female subjects. Administration of L-thyroxine led to consistent increases in serum T3 concentration (137 vs. 197 ng/100 ml), T3 distribution space (39.3 vs. 51.7 liters), T3 clearance rate (22.9 vs. 30.6 liters/day) and absolute T3 disposal rate (30 vs. 58 μg/day), but no change in apparent fractional turnover rate (60.3 vs. 60.6%/day). The proportion and absolute concentration of free T3 also increased during L-thyroxine administration. Increases in serum total T4 concentration (7.3 vs. 12.8 μg/100 ml) and in both the proportion and absolute concentration of free thyroxine also occurred. In five of the subjects, the kinetics of peripheral T4 turnover were simultaneously determined and a consistent increase in fractional turnover rate (9.7 vs. 14.2%/day), clearance rate (0.84 vs. 1.37 liters/day), and absolute disposal rate (64.2 vs. 185.0 μg/day) occurred during L-thyroxine administration. Despite these increases in the serum concentration and daily disposal rate of both T4 and T3, the patients were not clinically thyrotoxic. However, basal metabolic rate (BMR) values were marginally elevated and, as in frank thyrotoxicosis, T4-binding capacities of thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) reduced, suggesting that subclinical thyrotoxicosis was present. Thus, the often recommended replacement dose of 0.3 mg L-thyroxine daily may be greater than that required to achieve the euthyroid state.

The studies have also provided additional evidence of the peripheral conversion of T4 to T3 in man and have permitted the calculation that approximately one-third of exogenously administered T4 underwent deiodination to form T3. To the extent that a similar fractional conversion occurs in the normal state, it can be calculated that a major fraction of the T3 in serum derives from the peripheral deiodination of T4 and that only a lesser fraction derives from direct secretion by the thyroid gland.

Browse pages

Click on an image below to see the page. View PDF of the complete article

icon of scanned page 1010
page 1010
icon of scanned page 1011
page 1011
icon of scanned page 1012
page 1012
icon of scanned page 1013
page 1013
icon of scanned page 1014
page 1014
icon of scanned page 1015
page 1015
icon of scanned page 1016
page 1016
icon of scanned page 1017
page 1017
Version history
  • Version 1 (May 1, 1973): No description

Article tools

  • View PDF
  • Download citation information
  • Send a comment
  • Share this article
  • Terms of use
  • Standard abbreviations
  • Need help? Email the journal

Metrics

  • Article usage
  • Citations to this article

Go to

  • Top
  • Abstract
  • Version history
Advertisement
Advertisement

Copyright © 2022 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)

Sign up for email alerts