title: A simple method for estimating equilibrium constants for serum testosterone binding resulting in an optimal free testosterone index for use in elderly men.
abstract: An algorithm was developed to evaluate equilibrium constants for testosterone (Te) and sex hormone-binding globulin (SHBG) or albumin from serum free testosterone (FTe) measurements performed in a panel of 30 healthy elderly men by means of a near-reference method, i.e., symmetric dialysis (affinity constants: SHBG-Te, 1.13 x 10(9) L/mol; albumin-Te, 4.4 x 10(4) L/mol). Using these estimates, a free testosterone index (FTeI) was calculated from total Te and SHBG concentrations in a further 35 elderly men. This FTeI perfectly matches with actually measured free testosterone concentrations by symmetric dialysis in this second group, with a mean ratio index/measurement of 0.998+/-0.016 (SEM). The efficacy of the algorithm, which represents a simple alternative to previous cumbersome methods for estimation of equilibrium constants, is thereby demonstrated.
authors: Department of Chemical Endocrinology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. a.ross@ace.umcn.nl
authors: H Alec
authors: HA
authors: Ross
authors: Eric J
authors: EJ
authors: Meuleman
authors: Fred C G J
authors: FC
authors: Sweep
mesh_terms: D000368:Aged; D000465:Algorithms; D003956:Dialysis / Q000379:methods / Q000592:standards; D006801:Humans; D008297:Male; D008722:Methods; D008875:Middle Aged; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism; D012720:Severity of Illness Index; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000097:blood / Q000378:metabolism*
chemical_list: D012709:Serum Albumin; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone