Thyroid function testing

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Last reviewed: 15 Sep 2025
Last updated: 02 Apr 2024

Summary

Details

  • Thyroid hormone production
  • Thyroid hormone-binding proteins
  • Indications for TFTs: general considerations
  • Known thyroid dysfunction and preconception
  • Screening for thyroid dysfunction during pregnancy
  • Screening for congenital hypothyroidism
  • TFTs
  • Low TSH - associated with a high FT4 and/or FT3
  • Low TSH - associated with a low FT4 and/or FT3
  • Low TSH - associated with a normal FT4 and/or FT3
  • High TSH - associated with a high FT4 and/or FT3
  • High TSH - associated with a low FT4 and/or FT3
  • High TSH - associated with a normal FT4 and/or FT3
  • Normal TSH - associated with a low FT4 and/or FT3
  • Drug effects
Full details

Contributors

Authors

Joel Ehrenkranz, MD

Associate Professor

Division of Chemistry and Chemical Engineering

California Institute of Technology

Pasadena

CA

Disclosures

JE declares that he has served on a writing group for the American Thyroid Association which drafted an article on thyroid function testing and was submitted for publication to the journal Thyroid.

Acknowledgements

Dr Joel Ehrenkranz would like to gratefully acknowledge Dr Mae Sheikh-Ali, Dr Harshit Shah, Dr Melanie Thomas, Dr Anna Szafran-Swietlik, Dr Sandra Mesliniene, Dr Emad Naem, and Dr Abdul-Razzak Alamir, previous contributors to this topic. HS, MT, AS-S, SM, EN, and A-RA declare that they have no competing interests. MS-A declares she is a speaker for IBSA and AbbVie. Both have brand names for levothyroxine (LT4) medication.

Peer reviewers

Ronald Merrell, MD

Professor of Surgery

Virginia Commonwealth University

Richmond

VA

Disclosures

RM declares that he has no competing interests.

Georg Hennemann, MD

Professor of Medicine and Endocrinology

Medical Center Spijkenisse

The Hague

The Netherlands

Disclosures

Not disclosed.

Simon Pearce, MD

Professor of Endocrinology

Newcastle University

Endocrine Unit

Royal Victoria Infirmary

Newcastle upon Tyne

UK

Disclosures

SP declares that he has no competing interests.

V.S. Schneider, MD

Clinical Associate Professor of Medicine

Uniformed Services University of the Health Sciences

Bethesda

MD

MA and Senior Medical Advisor

NASA Headquarters

Washington

DC

Disclosures

VSS declares that he has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid. 2016 Oct;26(10):1343-1421.Full text  Abstract

Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults co-sponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid. 2012 Dec;22(12):1200-35.Full text  Abstract

Alexander EK, Pearce EN, Brent GA, et al. 2017 guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid. 2017 Mar;27(3):315-89.Full text  Abstract

National Institute for Health and Care Excellence. Thyroid disease: assessment and management. 2023 [internet publication].Full text

Reference articles

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