title: The effect of 5alpha-reductase inhibition with dutasteride and finasteride on semen parameters and serum hormones in healthy men.
abstract: BACKGROUND
  Dutasteride and finasteride are 5alpha-reductase inhibitors (5ARIs) that dramatically reduce serum levels of dihydrotestosterone (DHT).
  
  
  OBJECTIVE
  Because androgens are essential for fertility, we sought to determine the impact of 5ARI administration on serum testosterone (T), DHT, and spermatogenesis. DESIGN, SETTING, SUBJECTS, AND INTERVENTION: We conducted a randomized, double-blinded, placebo-controlled trial in 99 healthy men randomly assigned to receive dutasteride (D; 0.5 mg) (n = 33), finasteride (F; 5 mg) (n = 34), or placebo (n = 32) once daily for 1 yr.
  
  
  METHODS
  Blood and semen samples were collected at baseline and 26 and 52 wk of treatment and 24 wk after treatment and were assessed for T, DHT, and semen parameters.
  
  
  RESULTS
  D and F significantly (P < 0.001) suppressed serum DHT, compared with placebo (D, 94%; F, 73%) and transiently increased serum T. In both treatment groups, total sperm count, compared with baseline, was significantly decreased at 26 wk (D, -28.6%; F, -34.3%) but not at 52 wk (D, -24.9%; F, -16.2%) or the 24-wk follow-up (D, -23.3%; F, -6.2%). At 52 wk, semen volume was decreased (D, -29.7%; F, -14.5%, significantly for D) as was sperm concentration (D, -3.2%; [corrected] F, -7.4%, neither significant). There was a significant reduction of -6 to 12% in sperm motility during treatment with both D and F and at follow-up. Neither treatment had any effect on sperm morphology.
  
  
  CONCLUSIONS
  This study demonstrates that the decrease in DHT induced by 5ARIs is associated with mild decreases in semen parameters that appear reversible after discontinuation.
authors.affiliation: Department of Medicine, Veterans Affairs-Puget Sound Health Care System, University of Washington, Seattle, WA 98195, USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Amory
authors.forename: Christina
authors.initials: C
authors.lastname: Wang
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Swerdloff
authors.forename: Bradley D
authors.initials: BD
authors.lastname: Anawalt
authors.forename: Alvin M
authors.initials: AM
authors.lastname: Matsumoto
authors.forename: William J
authors.initials: WJ
authors.lastname: Bremner
authors.forename: Susan E
authors.initials: SE
authors.lastname: Walker
authors.forename: Lynda J
authors.initials: LJ
authors.lastname: Haberer
authors.forename: Richard V
authors.initials: RV
authors.lastname: Clark
mesh_terms: D058891:5-alpha Reductase Inhibitors; D000293:Adolescent; D000328:Adult; D001378:Azasteroids / Q000494:pharmacology*; D004311:Double-Blind Method; D000068538:Dutasteride; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018120:Finasteride / Q000494:pharmacology*; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012661:Semen / Q000187:drug effects*; D013076:Sperm Count; D013081:Sperm Motility / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D058891:5-alpha Reductase Inhibitors; D001378:Azasteroids; D004791:Enzyme Inhibitors; D006728:Hormones; D018120:Finasteride; D000068538:Dutasteride