title: Serum testosterone bioassay evaluation in a large male cohort.
abstract: OBJECTIVE
  To assess if a cell-based readout of androgen action in serum demonstrates a closer association with recognized classical parameters of androgen action in men than current measures of serum testosterone (T).
  
  
  METHODS
  To develop, validate and utilize a mammalian cell-based assay to measure specifically bioactive T and determine if this measure is a physiologically relevant fraction of serum T. MEASUREMENTS AND PARTICIPANTS: We have developed a specific serum T bioassay using human prostate cancer cells. A rapid 5-min exposure to 100% serum followed by serum withdrawal confers specificity of the assay to serum T and provides sufficient sensitivity to measure T in male serum samples. Matrix effects were experimentally discounted as a confounding issue. A total of 960 male serum samples from the Florey Adelaide Male Ageing Study (FAMAS) with previous comprehensive cohort data and serum measurements were utilized.
  
  
  RESULTS
  Bioassay T measurement in the 960 FAMAS serum samples returned a median of 10.7 nmol/l (1.7-45.4), and was most closely related to immunoassayed total T, but not immunoassayed bioavailable T or calculated free T. Immunoassayed total T demonstrated a positive association with isometric grip-strength (R(2) = 0.127, P < 0.001), self-reported sexual desire (R(2) = 0.113, P < 0.001) and erectile function (R(2) = 0.085, P < 0.05) while bioassay T did not.
  
  
  CONCLUSIONS
  While cellular bioassays offer a rapid and sensitive means of identifying the androgenic potential of complex environmental compounds, the utility of such assays in defining a clinically relevant fraction of serum T distinct from total T needs further investigation.
authors.affiliation: Molecular Ageing Laboratory, The Freemasons Foundation Centre for Mens Health, The University of Adelaide, Adelaide, Australia.
authors.forename: Eleanor F
authors.initials: EF
authors.lastname: Need
authors.forename: Peter D
authors.initials: PD
authors.lastname: O'Loughlin
authors.forename: David T
authors.initials: DT
authors.lastname: Armstrong
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Haren
authors.forename: Sean A
authors.initials: SA
authors.lastname: Martin
authors.forename: Wayne D
authors.initials: WD
authors.lastname: Tilley
authors.forename: Gary A
authors.initials: GA
authors.lastname: Wittert
authors.forename: Grant
authors.initials: G
authors.lastname: Buchanan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001681:Biological Assay / Q000379:methods* / Q000592:standards; D016466:CHO Cells; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D015331:Cohort Studies; D006224:Cricetinae; D003412:Cricetulus; D003940:Diagnostic Techniques, Endocrine / Q000592:standards; D006801:Humans; D008297:Male; D008875:Middle Aged; D013739:Testosterone / Q000032:analysis* / Q000097:blood* / Q000592:standards
chemical_list: D013739:Testosterone