Thyroid hormones thyroxine (T4) and tri-iodothyronine (T3) are produced, stored, and secreted by the thyroid gland. These hormones, particularly T3, play a major role in multiple biological and metabolic processes. They act by binding to thyroid receptors that are distributed in almost every organ. Typically, this process regulates gene transcription and the subsequent production of various proteins that are involved in development, growth, and cellular metabolism. Thyroid function tests (TFTs) are the most commonly used endocrine test. American Thyroid Association: thyroid function tests Opens in new window
- Thyroid hormone production
- Thyroid hormone-binding proteins
- Indications for TFTs: general considerations
- Known thyroid dysfunction and preconception
- Screening for thyroid dysfunction during pregnancy
- 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
Mae Sheikh-Ali, MD
Northeast Florida Endocrine & Diabetes Associates
MS-A declares that she is a speaker for Novo Nordisk, AstraZeneca, Amgen, Merck, Eli Lilly, Abbott, AbbVie, MannKind, Valeritas, and Janssen. MS-A declares that none of these are related to this topic.
Dr Mae Sheikh-Ali would like to gratefully acknowledge 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.
Ronald Merrell, MD
Professor of Surgery
Virginia Commonwealth University
RM declares that he has no competing interests.
Georg Hennemann, MD
Professor of Medicine and Endocrinology
Medical Center Spijkenisse
Simon Pearce, MD
Professor of Endocrinology
Royal Victoria Infirmary
Newcastle upon Tyne
SP declares that he has no competing interests.
V.S. Schneider, MD
Clinical Associate Professor of Medicine
Uniformed Services University of the Health Sciences
MA and Senior Medical Advisor
VSS declares that he has no competing interests.
Use of this content is subject to our disclaimer