Plasma free cortisol fraction reflects levels of functioning corticosteroid-binding globulin

Lewis, John G., Bagley, Christopher J., Elder, Peter A., Bachmann, Anthony W. and Torpy, David J. (2005) Plasma free cortisol fraction reflects levels of functioning corticosteroid-binding globulin. Clinica Chimica Acta, 359 1-2: 189-194. doi:10.1016/j.cccn.2005.03.044


Author Lewis, John G.
Bagley, Christopher J.
Elder, Peter A.
Bachmann, Anthony W.
Torpy, David J.
Title Plasma free cortisol fraction reflects levels of functioning corticosteroid-binding globulin
Journal name Clinica Chimica Acta   Check publisher's open access policy
ISSN 0009-8981
Publication date 2005
Sub-type Article (original research)
DOI 10.1016/j.cccn.2005.03.044
Volume 359
Issue 1-2
Start page 189
End page 194
Total pages 6
Editor A. H. Wu
J. Delanghe
Place of publication Netherlands
Publisher Elsevier BV
Collection year 2005
Language eng
Subject C1
321004 Endocrinology
730105 Endocrine organs and diseases (incl. diabetes)
Formatted abstract
Background

In normal plasma free cortisol accounts for less than 6% of the total with 80–90% bound to corticosteroid-binding globulin (CBG) and the remainder associated albumin. However little is known about the distribution of free cortisol in plasma where CBG is inactivated or in congenital CBG deficiency.

Methods and results


Here we describe ligand binding experiments revealing that while free cortisol in unstressed individuals is less than 6% of total cortisol this rises markedly to 25% when CBG is totally inactivated by heat. Similar elevations of the free cortisol fraction were noted in a patient with a rare genetically determined complete lack of CBG (mean 32% on frequent circadian sampling). Following heat inactivation of CBG or in the congenital absence of CBG, there is a shift in cortisol binding from CBG to albumin. That this shift occurs is further supported by experiments adding [3H]-cortisol to physiological human serum albumin solutions, where 25% of cortisol remained in the free fraction.

Conclusion


Taken together the data provide strong evidence that when CBG is inactivated or congenitally absent then more than 25% of the total cortisol appears in the free fraction with the remainder associated with albumin. The proportion of free cortisol measured in plasma thus reflects a simple measure of functional corticosteroid-binding globulin.
Keyword Medical Laboratory Technology
Free Cortisol
Cortisol
Corticosteroid-binding Globulin
Cbg
Albumin
Plasma
Linked-immunosorbent-assay
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
2006 Higher Education Research Data Collection
School of Medicine Publications
 
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Created: Wed, 15 Aug 2007, 06:49:30 EST