title: Three weeks of creatine monohydrate supplementation affects dihydrotestosterone to testosterone ratio in college-aged rugby players.
abstract: OBJECTIVE
  This study investigated resting concentrations of selected androgens after 3 weeks of creatine supplementation in male rugby players. It was hypothesized that the ratio of dihydrotestosterone (DHT, a biologically more active androgen) to testosterone (T) would change with creatine supplementation.
  
  
  METHODS
  Double-blind placebo-controlled crossover study with a 6-week washout period.
  
  
  METHODS
  Rugby Institute in South Africa.
  
  
  METHODS
  College-aged rugby players (n = 20) volunteered for the study, which took place during the competitive season.
  
  
  METHODS
  Subjects loaded with creatine (25 g/day creatine with 25 g/day glucose) or placebo (50 g/day glucose) for 7 days followed by 14 days of maintenance (5 g/day creatine with 25 g/day glucose or 30 g/day glucose placebo).
  
  
  METHODS
  Serum T and DHT were measured and ratio calculated at baseline and after 7 days and 21 days of creatine supplementation (or placebo). Body composition measurements were taken at each time point.
  
  
  RESULTS
  After 7 days of creatine loading, or a further 14 days of creatine maintenance dose, serum T levels did not change. However, levels of DHT increased by 56% after 7 days of creatine loading and remained 40% above baseline after 14 days maintenance (P < 0.001). The ratio of DHT:T also increased by 36% after 7 days creatine supplementation and remained elevated by 22% after the maintenance dose (P < 0.01).
  
  
  CONCLUSIONS
  Creatine supplementation may, in part, act through an increased rate of conversion of T to DHT. Further investigation is warranted as a result of the high frequency of individuals using creatine supplementation and the long-term safety of alterations in circulating androgen composition. STATEMENT OF CLINICAL RELEVANCE: Although creatine is a widely used ergogenic aid, the mechanisms of action are incompletely understood, particularly in relation to dihydrotestosterone, and therefore the long-term clinical safety cannot be guaranteed.
authors.affiliation: Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa.
authors.forename: Johann
authors.initials: J
authors.lastname: van der Merwe
authors.forename: Naomi E
authors.initials: NE
authors.lastname: Brooks
authors.forename: Kathryn H
authors.initials: KH
authors.lastname: Myburgh
mesh_terms: D000293:Adolescent; D000886:Anthropometry; D003401:Creatine / Q000494:pharmacology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D013196:Dihydrotestosterone / Q000097:blood*; D004311:Double-Blind Method; D005538:Football; D006801:Humans; D008297:Male; D013739:Testosterone / Q000097:blood*; D055815:Young Adult
chemical_list: D013196:Dihydrotestosterone; D013739:Testosterone; D003401:Creatine