PMID: 2495196Apr 1, 1989Paper

Dependence of the thyroxin/thyroxin-binding globulin (TBG) ratio and the free thyroxin index on TBG concentrations

Clinical Chemistry
J C Nelson, R T Tomei

Abstract

We studied the dependence of the free thyroxin (T4) index and the ratio of T4 to thyroxin-binding globulin (TBG) on TBG concentrations, using sera from cases of congenital TBG deficiency and congenital TBG excess. Two such sera with similar concentrations of albumin, transthyretin, and free T4 were mixed to provide test samples with TBG concentrations covering the range of clinical interest without changes in the other T4-binding proteins. Total T4, free T4, TBG, triiodothyronine (T3) uptake, and the free fraction of T3 in serum were measured, and we calculated the free T4 indices, T4/TBG ratios, and the free fraction of T4. A 100-fold variation in TBG concentration was associated with a 10-fold variation in total T4, a fourfold variation in T3 uptake, and a 10-fold variation in the T4/TBG ratio. As TBG concentrations increased, the T4/TBG ratio decreased and the free T4 index increased. The free T4 index did not parallel the T4/TBG ratio, and neither the T4/TBG ratio nor the free T4 index reflected the concentrations of free T4 in serum.

Related Concepts

Trending Feeds

COVID-19

Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Blastomycosis

Blastomycosis fungal infections spread through inhaling Blastomyces dermatitidis spores. Discover the latest research on blastomycosis fungal infections here.

Nuclear Pore Complex in ALS/FTD

Alterations in nucleocytoplasmic transport, controlled by the nuclear pore complex, may be involved in the pathomechanism underlying multiple neurodegenerative diseases including Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Here is the latest research on the nuclear pore complex in ALS and FTD.

Applications of Molecular Barcoding

The concept of molecular barcoding is that each original DNA or RNA molecule is attached to a unique sequence barcode. Sequence reads having different barcodes represent different original molecules, while sequence reads having the same barcode are results of PCR duplication from one original molecule. Discover the latest research on molecular barcoding here.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.

Evolution of Pluripotency

Pluripotency refers to the ability of a cell to develop into three primary germ cell layers of the embryo. This feed focuses on the mechanisms that underlie the evolution of pluripotency. Here is the latest research.

Position Effect Variegation

Position Effect Variagation occurs when a gene is inactivated due to its positioning near heterochromatic regions within a chromosome. Discover the latest research on Position Effect Variagation here.

STING Receptor Agonists

Stimulator of IFN genes (STING) are a group of transmembrane proteins that are involved in the induction of type I interferon that is important in the innate immune response. The stimulation of STING has been an active area of research in the treatment of cancer and infectious diseases. Here is the latest research on STING receptor agonists.

Microbicide

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections. Here is the latest research on microbicides.