title: Reduction in 24-hour plasma testosterone levels in subjects who showered 15 or 30 minutes after application of testosterone gel.
abstract: OBJECTIVE
  To investigate whether showering, to prevent the involuntary transfer of testosterone to others through skin contact, either 15 or 30 minutes after application of testosterone gel would significantly affect plasma testosterone levels.
  
  
  METHODS
  Prospective 3-way crossover trial.
  
  
  METHODS
  University hospital in the Netherlands.
  
  
  METHODS
  Ten agonadal female-to-male transsexuals who had sex-reassignment surgery at least 3 months earlier.
  
  
  METHODS
  Subjects were randomized to one of three application regimens for testosterone gel 50 mg/day, each lasting 7 days: testosterone application after showering (standard regimen), shower was taken 30 minutes after testosterone application, or shower was taken 15 minutes after testosterone application. Subjects then crossed over to each of the other two application regimens for a total of 21 days of study participation.
  
  
  RESULTS
  On day 7 of each application regimen, mean plasma testosterone levels were determined before testosterone application and at 1, 4, 7, and 10 hours after application. With the standard regimen, mean plasma testosterone levels at all time points after application were in the normal range: mean ± SD average concentration 994 ± 1026 ng/dl. When a shower was taken 30 or 15 minutes after application, plasma testosterone levels at 1, 4, 7, and 10 hours were significantly lower: mean ± SD average concentration 401 ± 231 ng/dl for 30 minutes after application (p<0.01) and 320 ± 248 ng/dl for 15 minutes after application (p<0.01).
  
  
  CONCLUSIONS
  Showering within 30 minutes after application of testosterone gel 50 mg/day reduces absorption of testosterone and results in unacceptably low plasma testosterone levels in most users. Therefore, this strategy cannot be recommended to prevent involuntary transfer of testosterone.
authors.affiliation: Department of Endocrinology, VU University Medical Center, Amsterdam, The Netherlands. p.deronde@vumc.nl
authors.forename: Willem
authors.initials: W
authors.lastname: de Ronde
authors.forename: Syarda
authors.initials: S
authors.lastname: Vogel
authors.forename: Hong N
authors.initials: HN
authors.lastname: Bui
authors.forename: Annemieke C
authors.initials: AC
authors.lastname: Heijboer
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D000728:Androgens / Q000097:blood* / Q000627:therapeutic use*; D001494:Baths; D018592:Cross-Over Studies; D004348:Drug Labeling; D005782:Gels / Q000627:therapeutic use; D005783:Gender Identity; D006785:Hospitals, University; D006801:Humans; D007006:Hypogonadism / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D057830:Gender-Affirming Surgery; D013739:Testosterone / Q000097:blood* / Q000378:metabolism / Q000627:therapeutic use*; D013997:Time Factors
chemical_list: D000728:Androgens; D005782:Gels; D013739:Testosterone