Abstract
Free thyroid hormones (free thyroxine, FT4, and free triiodothyronine, FT3) represent a more useful index of thyroid status than total thyroid hormones, because the latter are influenced by variations of thyroid hormone-binding proteins, especially T4-binding globulin (TBG). Thus, increased serum total T4 (TT4) and, in many instances, T3 (TT3) concentrations are encountered in euthyroid subjects with TBG excess, familial dysalbuminemic hyperthyroxinemia and transthyretin-associated hyperthyroxinemia, while decreased serum TT4 and TT3 levels are associated with TBG deficiency: under these circumstances, measurement of serum FT4 and FT3 levels correctly establishes the diagnosis of euthyroidism. In cases of suspected hyperthyroidism, a diagnostic strategy can be suggested based on serum FT3 (and TSH) measurement, since FT4 may occasionally be elevated, also in euthyroid subjects, e.g., in patients under chronic amiodarone or L-T4 treatment. When hypothyroidism is suspected, the most reliable test appears to be FT4 (together with TSH), because FT3 may still be normal in patients with subclinical or mild thyroid failure. In any case, it is essential that reliable free thyroid hormone assays be used, which are devoid of methodologic...Continue Reading
Citations
Jan 1, 2001·Indian Journal of Clinical Biochemistry : IJCB·J J FlemingA S Kanagasabapathy
Apr 17, 1998·Thyroid : Official Journal of the American Thyroid Association·I J Chopra
Oct 20, 1998·Thyroid : Official Journal of the American Thyroid Association·F Brucker-Davis
Feb 15, 2013·PLoS Genetics·Eleonora PorcuSilvia Naitza
Aug 28, 2003·Clinical Chemistry and Laboratory Medicine : CCLM·Michèle d'HerbomezRèmy Sapin
Aug 31, 2011·Pakistan Journal of Biological Sciences : PJBS·Reza Mansourian Azad
Apr 4, 2008·Journal of Preventive Medicine and Public Health = Yebang Ŭihakhoe Chi·Yoon-Young JangChae-Hoon Lee
Jan 28, 2015·Hormones and Behavior·Dafu YuRongrong Mao
Dec 1, 2011·Hormone Molecular Biology and Clinical Investigation·Radovan BílekVáclav Zamrazil
Dec 17, 2014·Toxicology·Yanyan ZhaoAlan D Steinman
Jan 27, 2016·The Journal of International Medical Research·Ning YangGuang Wang
Apr 3, 1999·Toxicology and Industrial Health·P Short, T Colborn
Sep 23, 2014·Korean journal of anesthesiology·Sang Hyun LeeYoung Ri Kim
May 15, 2003·Shock·Cara M ConnollyDavid N Herndon
Aug 25, 2015·Korean journal of pediatrics·Ye Seung LeePhil Soo Oh
Apr 19, 2005·Clinical Chemistry·Scott J CameronPaul W Ladenson
Jun 1, 2013·Hormone Molecular Biology and Clinical Investigation·Radovan BílekVáclav Zamrazil
Mar 31, 2017·Connective Tissue Research·Lorena Gabriela Rocha RibeiroRogéria Serakides
Aug 19, 2020·Journal of Endocrinological Investigation·E LiM K-S Leow
Aug 29, 1998·Clinical Biochemistry·R SapinD Grucker