title: Evidence that androgens modulate human thymic T cell output.
abstract: BACKGROUND
  The thymus has long been recognized as a target for the actions of androgenic hormones, but it has only been recently recognized that alterations in circulating levels of gonadal steroids might affect thymic output of T cells. We had the opportunity to examine parameters of thymic cellular output in several hypogonadal men undergoing androgen replacement therapy.
  
  
  METHODS
  Circulating naive (CD4+CD45RA+) T cells were quantitated by flow cytometric analysis of peripheral blood mononuclear cells. Cells bearing T-cell receptor excision circles were quantitated using real-time polymerase chain reaction amplification of DNA isolated from peripheral blood mononuclear cells from healthy men and from hypogonadal men before and after testosterone replacement therapy.
  
  
  RESULTS
  CD4+CD45+ (naive) T cells comprised 10.5% of lymphocytes in healthy males; this proportion was greatly increased in 2 hypogonadal men (35.5% and 44.4%). One man was studied sequentially during treatment with physiologic doses of testosterone. CD4+CD45RA+ cells fell from 37.36% to 20.05% after 1 month and to 12.51% after 7 months of normalized androgen levels. In 2 hypogonadal patients, T-cell receptor excision circle levels fell by 83% and 78% after androgen replacement therapy.
  
  
  CONCLUSIONS
  Our observations indicate that the hypogonadal state is associated with increased thymic output of T cells and that this increase in recent thymic emigrants in peripheral blood is reversed by androgen replacement.
authors.affiliation: Division of Rheumatology, Department of Medicine, The Pennsylvania State University, College of Medicine, Milton S. Hershey Medical Center, Hershey, PA 17033-0850, USA.
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Olsen
authors.forename: William J
authors.initials: WJ
authors.lastname: Kovacs
mesh_terms: D000328:Adult; D000728:Androgens / Q000494:pharmacology* / Q000627:therapeutic use; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects; D020249:Hormone Replacement Therapy; D006801:Humans; D007006:Hypogonadism / Q000188:drug therapy; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects*; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000728:Androgens; D011948:Receptors, Antigen, T-Cell; D017493:Leukocyte Common Antigens