An official website of the United States government

Levothroid

PubChem CID
23666112
Structure
Levothroid_small.png
Levothroid_3D_Structure.png
Molecular Formula
Synonyms
  • Levothyroxine sodium
  • L-Thyroxine sodium
  • 55-03-8
  • Euthyrox
  • Unithroid
Molecular Weight
798.85 g/mol
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Dates
  • Create:
    2008-02-05
  • Modify:
    2025-01-25
Description
Levothyroxine sodium anhydrous is the sodium salt of L-thyroxine. It is used as replacement therapy in the treatment of hypothyroidism. It contains a L-thyroxine(1-).
Levothyroxine Sodium is the sodium salt of levothyroxine, a synthetic levoisomer of thyroxine (T4) that is similar to the endogenous hormone produced by the thyroid gland. In peripheral tissues, levothyroxine is deiodinated by 5'-deiodinase to form triiodothyronine (T3). T3 enters the cell and binds to nuclear thyroid hormone receptors; the activated hormone-receptor complex in turn triggers gene expression and produces proteins required in the regulation of cellular respiration; thermogenesis; cellular growth and differentiation; and the metabolism of proteins, carbohydrates and lipids. T3 also exhibits cardiostimulatory effects.
The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (MONOIODOTYROSINE) and the coupling of iodotyrosines (DIIODOTYROSINE) in the THYROGLOBULIN. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form TRIIODOTHYRONINE which exerts a broad spectrum of stimulatory effects on cell metabolism.
See also: Levothyroxine (has active moiety).

1 Structures

1.1 2D Structure

Chemical Structure Depiction
Levothroid.png

1.2 3D Conformer

3D Conformer of Parent

2 Names and Identifiers

2.1 Computed Descriptors

2.1.1 IUPAC Name

sodium;(2S)-2-amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]propanoate
Computed by Lexichem TK 2.7.0 (PubChem release 2021.10.14)

2.1.2 InChI

InChI=1S/C15H11I4NO4.Na/c16-8-4-7(5-9(17)13(8)21)24-14-10(18)1-6(2-11(14)19)3-12(20)15(22)23;/h1-2,4-5,12,21H,3,20H2,(H,22,23);/q;+1/p-1/t12-;/m0./s1
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.3 InChIKey

YDTFRJLNMPSCFM-YDALLXLXSA-M
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.4 SMILES

C1=C(C=C(C(=C1I)OC2=CC(=C(C(=C2)I)O)I)I)C[C@@H](C(=O)[O-])N.[Na+]
Computed by OEChem 2.3.0 (PubChem release 2024.12.12)

2.2 Molecular Formula

C15H10I4NNaO4
Computed by PubChem 2.2 (PubChem release 2021.10.14)

2.3 Other Identifiers

2.3.1 CAS

55-03-8
25416-65-3

2.3.2 Deprecated CAS

50809-32-0, 67809-22-7

2.3.3 European Community (EC) Number

2.3.4 UNII

2.3.5 ChEBI ID

2.3.6 DSSTox Substance ID

2.3.7 KEGG ID

2.3.8 NCI Thesaurus Code

2.3.9 RXCUI

2.3.10 Wikidata

2.4 Synonyms

2.4.1 MeSH Entry Terms

  • 3,5,3',5'-Tetraiodothyronine
  • Berlthyrox
  • Dexnon
  • Eferox
  • Eltroxin
  • Eltroxine
  • Euthyrox
  • Eutirox
  • L Thyrox
  • L Thyroxin beta
  • L Thyroxin Henning
  • L Thyroxine
  • L Thyroxine Roche
  • L-3,5,3',5'-Tetraiodothyronine
  • L-Thyrox
  • L-Thyroxin beta
  • L-Thyroxin Henning
  • L-Thyroxine
  • L-Thyroxine Roche
  • Lévothyrox
  • Levo T
  • Levo-T
  • Levothroid
  • Levothyroid
  • Levothyroxin Deladande
  • Levothyroxin Delalande
  • Levothyroxine
  • Levothyroxine Sodium
  • Levoxine
  • Levoxyl
  • Novothyral
  • Novothyrox
  • O-(4-Hydroxy-3,5-diiodophenyl) 3,5-diiodo-L-tyrosine
  • O-(4-Hydroxy-3,5-diiodophenyl)-3,5-diiodotyrosine
  • Oroxine
  • Sodium Levothyroxine
  • Synthroid
  • Synthrox
  • T4 Thyroid Hormone
  • Thevier
  • Thyrax
  • Thyroid Hormone, T4
  • Thyroxin
  • Thyroxine
  • Tiroidine
  • Tiroxina Leo
  • Unithroid

2.4.2 Depositor-Supplied Synonyms

3 Chemical and Physical Properties

3.1 Computed Properties

Property Name
Molecular Weight
Property Value
798.85 g/mol
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Donor Count
Property Value
2
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Acceptor Count
Property Value
5
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Rotatable Bond Count
Property Value
5
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Exact Mass
Property Value
798.6686 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Monoisotopic Mass
Property Value
798.6686 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Topological Polar Surface Area
Property Value
95.6 Ų
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Heavy Atom Count
Property Value
25
Reference
Computed by PubChem
Property Name
Formal Charge
Property Value
0
Reference
Computed by PubChem
Property Name
Complexity
Property Value
426
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Isotope Atom Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Atom Stereocenter Count
Property Value
1
Reference
Computed by PubChem
Property Name
Undefined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Covalently-Bonded Unit Count
Property Value
2
Reference
Computed by PubChem
Property Name
Compound Is Canonicalized
Property Value
Yes
Reference
Computed by PubChem (release 2021.10.14)

3.2 Chemical Classes

3.2.1 Drugs

3.2.1.1 Human Drugs
Breast Feeding; Lactation; Milk, Human; Thyroid Hormones
Breast Feeding; Lactation; Thyroid Hormones
Human drug -> Prescription
Human drug -> Prescription; Discontinued
Human drug -> Prescription; Discontinued; Active ingredient (LEVOTHYROXINE SODIUM)
3.2.1.2 Animal Drugs
Active Ingredients (Levothyroxine sodium) -> FDA Greenbook

5 Chemical Vendors

6 Drug and Medication Information

6.1 Drug Classes

Breast Feeding; Lactation; Milk, Human; Thyroid Hormones
Breast Feeding; Lactation; Thyroid Hormones

6.2 FDA Approved Drugs

6.3 FDA Orange Book

6.4 FDA National Drug Code Directory

6.5 FDA Green Book

6.6 Drug Labels

Drug and label
Active ingredient and drug

6.7 Clinical Trials

6.7.1 ClinicalTrials.gov

6.7.2 EU Clinical Trials Register

7 Pharmacology and Biochemistry

7.1 FDA Pharmacological Classification

1 of 2
Non-Proprietary Name
LEVOTHYROXINE SODIUM
Pharmacological Classes
2 of 2
Non-Proprietary Name
LEVOTHYROXINE SODIUM ANHYDROUS
Pharmacological Classes

7.2 ATC Code

H - Systemic hormonal preparations, excl. sex hormones and insulins

H03 - Thyroid therapy

H03A - Thyroid preparations

H03AA - Thyroid hormones

H03AA01 - Levothyroxine sodium

8 Use and Manufacturing

8.1 Uses

Use (kg) in Switzerland (2009): >5

Use (kg; approx.) in Germany (2009): >100

Use (kg) in USA (2002): 173

Use (kg) in France (2004): 59

Consumption (g per capita) in Switzerland (2009): 0.00064

Consumption (g per capita; approx.) in Germany (2009): 0.0012

Consumption (g per capita) in the USA (2002): 0.00061

Consumption (g per capita) in France (2004): 0.00098

Excretion rate: 0.5

Calculated removal (%): 35.8

8.1.1 Use Classification

Animal Drugs -> FDA Approved Animal Drug Products (Green Book) -> Active Ingredients
Human Drugs -> FDA Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book) -> Active Ingredients

8.2 General Manufacturing Information

EPA TSCA Commercial Activity Status
L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, sodium salt (1:1): INACTIVE

9 Safety and Hazards

9.1 Hazards Identification

9.1.1 GHS Classification

1 of 2
View All
Pictogram(s)
Health Hazard
Signal
Danger
GHS Hazard Statements

H361 (94.2%): Suspected of damaging fertility or the unborn child [Warning Reproductive toxicity]

H372 (94.2%): Causes damage to organs through prolonged or repeated exposure [Danger Specific target organ toxicity, repeated exposure]

Precautionary Statement Codes

P203, P260, P264, P270, P280, P318, P319, P405, and P501

(The corresponding statement to each P-code can be found at the GHS Classification page.)

ECHA C&L Notifications Summary

Aggregated GHS information provided per 52 reports by companies from 4 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown.

9.1.2 Hazard Classes and Categories

Repr. 2 (94.2%)

STOT RE 1 (94.2%)

STOT RE 1 (75%)

STOT RE 2 (25%)

9.2 Other Safety Information

Chemical Assessment

IMAP assessments - L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, monosodium salt: Human health tier I assessment

IMAP assessments - L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, monosodium salt: Environment tier I assessment

10 Toxicity

10.1 Toxicological Information

10.1.1 Effects During Pregnancy and Lactation

◉ Summary of Use during Lactation

Levothyroxine (T4) is a normal component of human milk. Limited data on exogenous replacement doses of levothyroxine during breastfeeding indicate no adverse effects in infants. The American Thyroid Association recommends that subclinical and overt hypothyroidism should be treated with levothyroxine in lactating women seeking to breastfeed. Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers with low milk supply. Levothyroxine dosage requirement may be increased in the postpartum period compared to prepregnancy requirements in patients with Hashimoto's thyroiditis.

◉ Effects in Breastfed Infants

Effects of exogenous thyroid hormone administration to mothers on their infant have not been reported. One case of apparent mitigation of cretinism in hypothyroid infants by breastfeeding has been reported, but the amounts of thyroid hormones in milk are not optimal, and this result has been disputed. The thyroid hormone content of human milk from the mothers of very preterm infants appears not to be sufficient to affect the infants' thyroid status. The amounts of thyroid hormones in milk are apparently not sufficient to interfere with diagnosis of hypothyroidism.

In a telephone follow-up study, 5 nursing mothers reported taking levothyroxine (dosage unspecified). The mothers reported no adverse reactions in their infants.

One mother who had undergone a thyroidectomy was taking levothyroxine 100 mcg daily as well as calcium carbonate and calcitriol. Her breastfed infant was reportedly "thriving" at 3 months of age.

A woman with propionic acidemia took levothyroxine 50 mcg daily as well as biotin, carnitine, and various amino acids while exclusively breastfeeding her infant for 2 months and nonexclusively for 10 months. At that time, the infant had normal growth and development.

◉ Effects on Lactation and Breastmilk

Adequate thyroid hormone serum levels are required for normal lactation. Replacing deficient thyroid levels should improve milk production caused by hypothyroidism. Supraphysiologic doses would not be expected to further improve lactation.

◉ Summary of Use during Lactation

Thyroid is an animal-derived mixture of levothyroxine (T4) and liothyronine (T3), which are normal components of human milk. Limited data on exogenous replacement doses of levothyroxine during breastfeeding indicate no adverse effects in infants. If thyroid is required by the mother, it is not a reason to discontinue breastfeeding. The American Thyroid Association recommends that subclinical and overt hypothyroidism should be treated with levothyroxine in lactating women seeking to breastfeed. Thyroid dosage requirement may be increased in the postpartum period compared to prepregnancy requirements patients with Hashimoto's thyroiditis.

◉ Effects in Breastfed Infants

Effects of exogenous thyroid hormone administration to mothers on their infant have not been reported. One case of apparent mitigation of cretinism in hypothyroid infants by breastfeeding has been reported, but the amounts of thyroid hormones in milk are not optimal, and this result has been disputed. The thyroid hormone content of human milk from the mothers of very preterm infants appears not to be sufficient to affect the infants' thyroid status. The amounts of thyroid hormones in milk are apparently not sufficient to interfere with diagnosis of hypothyroidism.

In a telephone follow-up study, 5 nursing mothers reported taking levothyroxine (dosage unspecified). The mothers reported no adverse reactions in their infants.

One mother with who had undergone a thyroidectomy was taking levothyroxine 100 mcg daily as well as calcium carbonate and calcitriol. Her breastfed infant was reportedly "thriving" at 3 months of age.

◉ Effects on Lactation and Breastmilk

Adequate thyroid hormone serum levels are required for normal lactation. Replacing deficient thyroid levels should improve milk production caused by hypothyroidism. Supraphysiologic doses would not be expected to further improve lactation.

10.1.2 Acute Effects

11 Literature

11.1 Consolidated References

11.2 NLM Curated PubMed Citations

11.3 Springer Nature References

11.4 Chemical Co-Occurrences in Literature

11.5 Chemical-Gene Co-Occurrences in Literature

11.6 Chemical-Disease Co-Occurrences in Literature

12 Patents

12.1 Depositor-Supplied Patent Identifiers

12.2 WIPO PATENTSCOPE

12.3 FDA Orange Book Patents

12.4 Chemical Co-Occurrences in Patents

12.5 Chemical-Disease Co-Occurrences in Patents

12.6 Chemical-Gene Co-Occurrences in Patents

13 Classification

13.1 MeSH Tree

13.2 NCI Thesaurus Tree

13.3 ChEBI Ontology

13.4 KEGG: USP

13.5 KEGG: ATC

13.6 KEGG: Target-based Classification of Drugs

13.7 KEGG: Drug Groups

13.8 WHO ATC Classification System

13.9 ChemIDplus

13.10 UN GHS Classification

13.11 NORMAN Suspect List Exchange Classification

13.12 EPA DSSTox Classification

13.13 EPA TSCA and CDR Classification

13.14 FDA Drug Type and Pharmacologic Classification

13.15 EPA Substance Registry Services Tree

14 Information Sources

  1. Australian Industrial Chemicals Introduction Scheme (AICIS)
    L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, monosodium salt
    https://services.industrialchemicals.gov.au/search-assessments/
  2. ChemIDplus
    ChemIDplus Chemical Information Classification
    https://pubchem.ncbi.nlm.nih.gov/source/ChemIDplus
  3. EPA Chemicals under the TSCA
    L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, sodium salt (1:1)
    https://www.epa.gov/chemicals-under-tsca
    EPA TSCA Classification
    https://www.epa.gov/tsca-inventory
  4. EPA DSSTox
    CompTox Chemicals Dashboard Chemical Lists
    https://comptox.epa.gov/dashboard/chemical-lists/
  5. European Chemicals Agency (ECHA)
    LICENSE
    Use of the information, documents and data from the ECHA website is subject to the terms and conditions of this Legal Notice, and subject to other binding limitations provided for under applicable law, the information, documents and data made available on the ECHA website may be reproduced, distributed and/or used, totally or in part, for non-commercial purposes provided that ECHA is acknowledged as the source: "Source: European Chemicals Agency, http://echa.europa.eu/". Such acknowledgement must be included in each copy of the material. ECHA permits and encourages organisations and individuals to create links to the ECHA website under the following cumulative conditions: Links can only be made to webpages that provide a link to the Legal Notice page.
    https://echa.europa.eu/web/guest/legal-notice
    L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, monosodium salt, hydrate
    https://echa.europa.eu/substance-information/-/substanceinfo/100.211.289
    L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, monosodium salt, hydrate (EC: 685-634-1)
    https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/216340
  6. FDA Global Substance Registration System (GSRS)
    LICENSE
    Unless otherwise noted, the contents of the FDA website (www.fda.gov), both text and graphics, are not copyrighted. They are in the public domain and may be republished, reprinted and otherwise used freely by anyone without the need to obtain permission from FDA. Credit to the U.S. Food and Drug Administration as the source is appreciated but not required.
    https://www.fda.gov/about-fda/about-website/website-policies#linking
  7. ChEBI
  8. NCI Thesaurus (NCIt)
    LICENSE
    Unless otherwise indicated, all text within NCI products is free of copyright and may be reused without our permission. Credit the National Cancer Institute as the source.
    https://www.cancer.gov/policies/copyright-reuse
  9. ClinicalTrials.gov
    LICENSE
    The ClinicalTrials.gov data carry an international copyright outside the United States and its Territories or Possessions. Some ClinicalTrials.gov data may be subject to the copyright of third parties; you should consult these entities for any additional terms of use.
    https://clinicaltrials.gov/ct2/about-site/terms-conditions#Use
  10. DailyMed
  11. Drugs and Lactation Database (LactMed)
  12. Drugs@FDA
    LICENSE
    Unless otherwise noted, the contents of the FDA website (www.fda.gov), both text and graphics, are not copyrighted. They are in the public domain and may be republished, reprinted and otherwise used freely by anyone without the need to obtain permission from FDA. Credit to the U.S. Food and Drug Administration as the source is appreciated but not required.
    https://www.fda.gov/about-fda/about-website/website-policies#linking
  13. EU Clinical Trials Register
  14. FDA Approved Animal Drug Products (Green Book)
    LICENSE
    Unless otherwise noted, the contents of the FDA website (www.fda.gov), both text and graphics, are not copyrighted. They are in the public domain and may be republished, reprinted and otherwise used freely by anyone without the need to obtain permission from FDA. Credit to the U.S. Food and Drug Administration as the source is appreciated but not required.
    https://www.fda.gov/about-fda/about-website/website-policies#linking
  15. FDA Orange Book
    LICENSE
    Unless otherwise noted, the contents of the FDA website (www.fda.gov), both text and graphics, are not copyrighted. They are in the public domain and may be republished, reprinted and otherwise used freely by anyone without the need to obtain permission from FDA. Credit to the U.S. Food and Drug Administration as the source is appreciated but not required.
    https://www.fda.gov/about-fda/about-website/website-policies#linking
  16. KEGG
    LICENSE
    Academic users may freely use the KEGG website. Non-academic use of KEGG generally requires a commercial license
    https://www.kegg.jp/kegg/legal.html
    Anatomical Therapeutic Chemical (ATC) classification
    http://www.genome.jp/kegg-bin/get_htext?br08303.keg
    Target-based classification of drugs
    http://www.genome.jp/kegg-bin/get_htext?br08310.keg
  17. National Drug Code (NDC) Directory
    LICENSE
    Unless otherwise noted, the contents of the FDA website (www.fda.gov), both text and graphics, are not copyrighted. They are in the public domain and may be republished, reprinted and otherwise used freely by anyone without the need to obtain permission from FDA. Credit to the U.S. Food and Drug Administration as the source is appreciated but not required.
    https://www.fda.gov/about-fda/about-website/website-policies#linking
  18. NLM RxNorm Terminology
    LICENSE
    The RxNorm Terminology is created by the National Library of Medicine (NLM) and is in the public domain and may be republished, reprinted and otherwise used freely by anyone without the need to obtain permission from NLM. Credit to the U.S. National Library of Medicine as the source is appreciated but not required. The full RxNorm dataset requires a free license.
    https://www.nlm.nih.gov/research/umls/rxnorm/docs/termsofservice.html
    levothyroxine sodium anhydrous
    https://rxnav.nlm.nih.gov/id/rxnorm/1372638
  19. NORMAN Suspect List Exchange
    LICENSE
    Data: CC-BY 4.0; Code (hosted by ECI, LCSB): Artistic-2.0
    https://creativecommons.org/licenses/by/4.0/
    LEVOTHYROXINE SODIUM
    NORMAN Suspect List Exchange Classification
    https://www.norman-network.com/nds/SLE/
  20. Springer Nature
  21. WHO Anatomical Therapeutic Chemical (ATC) Classification
    LICENSE
    Use of all or parts of the material requires reference to the WHO Collaborating Centre for Drug Statistics Methodology. Copying and distribution for commercial purposes is not allowed. Changing or manipulating the material is not allowed.
    https://www.whocc.no/copyright_disclaimer/
  22. Wikidata
  23. Medical Subject Headings (MeSH)
    LICENSE
    Works produced by the U.S. government are not subject to copyright protection in the United States. Any such works found on National Library of Medicine (NLM) Web sites may be freely used or reproduced without permission in the U.S.
    https://www.nlm.nih.gov/copyright.html
  24. PubChem
  25. GHS Classification (UNECE)
  26. EPA Substance Registry Services
  27. PATENTSCOPE (WIPO)
CONTENTS