title: Use of biomarkers to assess tissue specific androgen adequacy: defining male hypogonadism.
abstract: OBJECTIVE
  The criteria for normal testosterone have been established by expert consensus rather than by evidence. We determined whether a cutoff point for normal could be established using biomarkers.
  
  
  METHODS
  We performed an exploratory investigation of 1,492 hypogonadal men pooled from 7 registration trials. Serum testosterone, prostate specific antigen and hematocrit were measured at baseline and after 90 days of continuous testosterone replacement therapy.
  
  
  RESULTS
  Baseline prostate specific antigen, percent change in prostate specific antigen and hematocrit appeared to be most strongly related to baseline serum testosterone. Subgroup analysis and visual inspection of linear spline fit of these data suggested an approximate serum testosterone cutoff for normal of 300 ng/dl for percent change in hematocrit, and 200 ng/dl for baseline prostate specific antigen and percent change in prostate specific antigen.
  
  
  CONCLUSIONS
  This exploratory study revealed considerable variation among individuals and target tissues in individuals. Further study should be performed using standardized assays in a broader population.
authors.affiliation: Division of Reproductive and Urologic Products, Office of New Drugs, Food and Drug Administration, Silver Spring, Maryland 20993, USA. jonathan.jarow@fda.hhs.gov
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Jarow
authors.forename: John
authors.initials: J
authors.lastname: Troiani
authors.forename: Donald
authors.initials: D
authors.lastname: McNellis
authors.forename: Roger
authors.initials: R
authors.lastname: Wiederhorn
authors.forename: Guodong
authors.initials: G
authors.lastname: Fang
authors.forename: Harry
authors.initials: H
authors.lastname: Handelsman
mesh_terms: D015415:Biomarkers / Q000097:blood; D020249:Hormone Replacement Therapy; D006801:Humans; D007006:Hypogonadism / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013739:Testosterone / Q000097:blood* / Q000627:therapeutic use*
chemical_list: D015415:Biomarkers; D013739:Testosterone