Free testosterone: clinical utility and important analytical aspects of measurement.
Level 5 - mechanism / opinion, no new human data
Narrative review without systematic search or primary empirical data
PubMed 24783351 · doi:10.1016/b978-0-12-800094-6.00002-9
What was done
This narrative review evaluated the clinical utility and analytical methods for measuring free and bioavailable testosterone in routine clinical laboratories. It covers testosterone synthesis and protein binding, clinical indications including male hypogonadism and female androgen excess, and technical aspects of measurement methods including equilibrium dialysis, ultrafiltration, analog immunoassay, calculation equations, selective protein precipitation, and liquid chromatography-tandem mass spectrometry.
What was found
The abstract states that circulating testosterone concentrations are approximately 15 to 25 times higher in adult men compared to women, and that most circulating testosterone is bound to sex hormone-binding globulin or albumin. Beyond these physiological values, the abstract provides no quantitative analytical comparisons, diagnostic accuracy metrics, or numerical performance data for the reviewed measurement techniques.
Why it matters
Free and bioavailable testosterone measurements provide diagnostic value in disorders of androgen deficiency or excess where total testosterone may be misleading due to binding protein variations. Summarizing the practical and analytical trade-offs of reference, automated, and calculation methods guides clinical laboratory test selection.
Limits
This paper is a narrative review without primary empirical data, systematic search criteria, or meta-analytic pooling. The abstract omits quantitative comparisons of method precision, accuracy, or bias.
Cited by
- supports Sex hormone-binding globulin (SHBG) binds approximately 60% of total testosterone, albumin binds about 38%, and free testosterone makes up roughly 2% to 3%.
- supports Equilibrium dialysis and equilibrium ultrafiltration are direct measurement assays for free testosterone rather than calculated estimates.