Finally references the Fiers paper.
*If an equilibrium dialysis assay is not available, free testosterone concentration should be estimated using an equation that provides a close approximation of values derived using the equilibrium dialysis method.57
Although again he is still dead set on pushing the newer Ensemble Allosteric Model hinting at what may be coming???
As I have stated numerous times on the forum, patiently waiting on the completion of Phase II for the TruT™algorithm (cFTZ) let alone standardization and harmonized reference ranges for Free testosterone which is in the works as we speak.
*Two categories of algorithms to calculate FT from the TT, SHBG, and albumin levels have been published; the linear equations that are based on the assumption of a simple linear model of testosterone's binding to SHBG and human serum albumin with a single fixed Kd, and those that are empirically derived from regression analyses of the relation between free testosterone and total testosterone and SHBG levels. The linear equations for FT estimation are based on the assumption that each SHBG dimer binds two testosterone molecules and that the two binding sites on SHBG have similar binding affinity; these assumptions are not supported by our current understanding of the dynamics of testosterone's binding to SHBG. cFT values obtained using a multi-step, allosteric ensemble model are much closer to those obtained using equilibrium dialysis. 7,49
*Testosterone levels should be measured preferably in a CDCcertified laboratory using validated assays; in cases of equivocal TT concentration and/or abnormal SHBG levels, free testosterone levels should be measured using equilibrium dialysis or calculated using an equation based on our current understanding of the dynamics of testosterone binding, such as the ensemble allostery model
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