Free Testosterone

Discussion in 'Men's Health Forum' started by Michael Scally MD, Mar 29, 2018.

  1. Michael Scally MD

    Michael Scally MD Doctor of Medicine

    Reassessing Free testosterone Calculation by Liquid Chromatography-Tandem-Mass- Spectrometry Direct Equilibrium Dialysis

    BACKGROUND - Assessment of free testosterone (FT) might help evaluate androgen status in subjects with borderline total testosterone (T) and/or altered SHBG levels. However, validity of different methods to measure or calculate FT is matter for debate.

    METHODS - Serum from 183 women and 146 men was analysed using equilibrium dialysis (ED) with FT directly measured by LC/MS-MS. FT calculation was re-evaluated for the mass action law-based equation according to Vermeulen (cFT-V) , empirical equations according to Ly (cFT-L) and a recently proposed calculation based on a multi-step, dynamic, allosteric model according to Zakharov (cFT-Z).

    RESULTS - FT by ED [median13 pmol/L(1.2% of T) in women; 248 pmol/L(1.5% of T) in men] was strongly inversely correlated to SHBG and significantly to albumin in women and only weakly to SHBG in men. Median (p2.5-p97.5) ratio of cFT over ED-FT (EMAS samples) was 1.19 (0.9-1.47),1.00 (0.69-1.42) and 2.05 (1.26-3.26) for cFT-V, cFT-L and cFT-Z.

    Ratio for cFT-V was not significantly affected by SHBG, T or albumin levels (rank correlations 0.17 to -0.01); ratios for cFT-L and cFT-Z were affected (p<0.05 to p<0.001) and strongly correlated to SHBG (rank correlations 0.72 and 0.75). Rank correlation between cFT% and ED-FT% (for men) are 0.62, 0.74 and 0.89 for cFT-Z, cFT-L and cFT-V.

    CONCLUSION - FT results by direct ED confirm prior FT data from indirect ED and ultrafiltration methodologies. Calculations have inherent limitations with clinically important differences among evaluated equations: cFT-V, although overestimating FT, appears the most robust approximation, largely independent of SHBG, albumin and T levels.

    Fiers T, Wu F, Moghetti P, Vanderschueren D, Lapauw B, Kaufman JM. Reassessing free testosterone calculation by liquid chromatography-tandem-mass- spectrometry direct equilibrium dialysis. The Journal of Clinical Endocrinology & Metabolism 2018. Reassessing free testosterone calculation by liquid chromatography-tandem-mass- spectrometry direct equilibrium dialysis | The Journal of Clinical Endocrinology & Metabolism | Oxford Academic