J Sex Med. 2006 Nov;3(6):1085-9.
Wide variability in laboratory reference values for serum testosterone.
Lazarou S, Reyes-Vallejo L, Morgentaler A.
Harvard Medical School, Division of Urology, Beth Israel Deaconess Medical Center, Boston, MA, USA.
INTRODUCTION: The laboratory determination of testosterone levels consistent with a diagnosis of hypogonadism is complicated by the availability of multiple testosterone assays and varying reference ranges.
AIM: To assess current laboratory practices regarding availability of testosterone assays and use of reference values.
METHODS: A telephone survey of 12 academic, 12 community medical laboratories, and one national laboratory.
MAIN OUTCOME MEASURES: Types of androgen assays offered and determination of reference values.
RESULTS: All of the academic and eight of the community centers performed total testosterone testing. Free testosterone was performed in-house by six of the 12 academic and one community center. Testing for bioavailable testosterone, free androgen index, and percent free testosterone was performed in-house by no more than two centers. There were eight and four different assays used for total and free testosterone, respectively. One national laboratory offered equilibrium dialysis measurement of free testosterone. Of the 25 labs, there were 17 and 13 different sets of reference values for total and free testosterone, respectively. The low reference value for total testosterone ranged from 130 to 450 ng/dL (350% difference), and the upper value ranged from 486 to 1,593 ng/dL (325% difference). Age-adjusted reference values were applied in four centers for total testosterone and in seven labs for free testosterone. All reference values were based on a standard statistical model without regard for clinical aspects of hypogonadism. Twenty-three of the 25 lab directors responded that clinically relevant testosterone reference ranges would be preferable to current standards.
CONCLUSIONS: Laboratory reference values for testosterone vary widely, and are established without clinical considerations.
Testosterone Threshold Levels and Lean Tissue Mass Targets Needed to Enhance Skeletal Muscle Strength and Function: The HORMA Trial
Methods. One hundred and twelve men aged 65–90 years received testosterone gel (5 g/d vs 10 g/d via Leydig cell clamp) and rhGH (0 vs 3 vs 5 ***956;g/kg/d) in a double-masked 2 × 3 factorial design for 16 weeks. Outcomes included lean tissue mass by dual energy x-ray absorptiometry, one-repetition maximum strength, Margaria stair power, and activity questionnaires. We used pathway analysis to determine the relationship between changes in hormone levels, muscle mass, strength, and function.
Results. Increases in total testosterone of 1046 ng/dL (95% confidence interval = 1040–1051) and 898 ng/dL (95% confidence interval = 892–904) were necessary to achieve median increases in lean body mass of 1.5 kg and appendicular skeletal muscle mass of 0.8 kg, respectively, which were required to significantly enhance one-repetition maximum strength (***8805;30%). Co-treatment with rhGH lowered the testosterone levels (quantified using liquid chromatography–tandem mass spectrometry) necessary to reach these lean mass thresholds.
Increases in total testosterone of 1046 and 898 ng/dL were required for participants only receiving testosterone (rhGH placebo) to achieve threshold improvements in LBM and ASMM, respectively; these corresponded to increases in free testosterone of 477 and 397 pg/mL. These represent conservative estimates because they include men whose testosterone levels declined, as may occur during clinical treatment with testosterone, and as such delineate target testosterone levels needed to sufficiently enhance LBM and ASMM necessary to improve muscle strength and physical function. Our data may also help explain why some testosterone trials, which used relatively low fixed doses of testosterone and achieved small (if any) increments in testosterone levels, reported relatively modest LBM gains and little or no change in muscle strength or physical function
Total testosterone levels by liquid chromatography–tandem mass spectrometry were on average ***8764;130 ng/dL higher than those obtained by the automated platform immunoassays. It is possible that serum level targets may differ when other assays are used to quantify serum testosterone levels. Changes in free testosterone performed comparable to total testosterone in their ability to predict changes in LBM or ASMM.
So - my questions are these
1) Are we putting too much value on lab test results if they are statistical and not clinically based?
2) Should we be aiming for higher testosterone levels - say 1000-1200 ngs/dL?
3) Does this study prove a valid reason for using hgh in that - per the study - the addition of small amounts of hgh will reduce the amount of testosterone needed?
4) What methods are used to determine total testosterone levels at Lab Corp and Quest?
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