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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone and Men's Health Articles
Harmonized reference ranges for Total and Free T levels
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<blockquote data-quote="madman" data-source="post: 218720" data-attributes="member: 13851"><p><em><strong>*Because of the complexities in the current methods of measuring free testosterone, several equations have been published for the calculation of free testosterone concentrations from total testosterone, SHBG, and albumin concentrations.27–31</strong> <strong>These equations can be broadly categorized into those that use the <u>law of mass action equations27,29,31 and those that are deriving empirically using regression methods</u>.30 </strong></em></p><p><em><strong></strong></em></p><p><em><strong>*The law of mass action equations, such as those published by Sodergard and colleagues,27 Vermeulen and colleagues,29 and Mazer,31 are <u>based on the assumptions of linear binding of testosterone to SHBG with a fixed association constant</u>. <u>Furthermore, these equations assume that testosterone binds to a single binding site on human serum albumin with low affinity</u></strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Recent studies using modern biophysical techniques have shown that the <u>binding of testosterone and estradiol to SHBG is a dynamic nonlinear process that involves an allosteric interaction between the 2 SHBG monomers, such that the Kd varies dynamically across the range of sex hormone and SHBG concentrations</u>28,32 (Fig. 3)</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*The estimates of free testosterone concentration using the novel <u>Ensemble Allostery Model</u> match closely the concentrations measured derived by the equilibrium dialysis method.28</strong> </em></p><p><em></em></p><p><em><strong>*<u>All algorithms are highly dependent on the accuracy and sensitivity of the total testosterone and SHBG assays</u>. Furthermore, recent studies of testosterone’s binding to human serum albumin using 2-dimensional nuclear magnetic resonance and fluorescence spectroscopy have <u>revealed the presence of multiple, allosterically coupled binding sites for testosterone on albumin</u>33 (see Fig. 3) </strong></em></p></blockquote><p></p>
[QUOTE="madman, post: 218720, member: 13851"] [I][B]*Because of the complexities in the current methods of measuring free testosterone, several equations have been published for the calculation of free testosterone concentrations from total testosterone, SHBG, and albumin concentrations.27–31[/B] [B]These equations can be broadly categorized into those that use the [U]law of mass action equations27,29,31 and those that are deriving empirically using regression methods[/U].30 *The law of mass action equations, such as those published by Sodergard and colleagues,27 Vermeulen and colleagues,29 and Mazer,31 are [U]based on the assumptions of linear binding of testosterone to SHBG with a fixed association constant[/U]. [U]Furthermore, these equations assume that testosterone binds to a single binding site on human serum albumin with low affinity[/U] *Recent studies using modern biophysical techniques have shown that the [U]binding of testosterone and estradiol to SHBG is a dynamic nonlinear process that involves an allosteric interaction between the 2 SHBG monomers, such that the Kd varies dynamically across the range of sex hormone and SHBG concentrations[/U]28,32 (Fig. 3) *The estimates of free testosterone concentration using the novel [U]Ensemble Allostery Model[/U] match closely the concentrations measured derived by the equilibrium dialysis method.28[/B] [B]*[U]All algorithms are highly dependent on the accuracy and sensitivity of the total testosterone and SHBG assays[/U]. Furthermore, recent studies of testosterone’s binding to human serum albumin using 2-dimensional nuclear magnetic resonance and fluorescence spectroscopy have [U]revealed the presence of multiple, allosterically coupled binding sites for testosterone on albumin[/U]33 (see Fig. 3) [/B][/I] [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone and Men's Health Articles
Harmonized reference ranges for Total and Free T levels
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