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Three Weeks of Creatine Monohydrate Supplementation Affects Dihydrotestosterone to Testosterone Ratio in College-Aged Rugby Players

van der Merwe, Johann MBChB; Brooks, Naomi E PhD; Myburgh, Kathryn H PhD

Clinical Journal of Sport Medicine: September 2009 - Volume 19 - Issue 5 - p 399-404
doi: 10.1097/JSM.0b013e3181b8b52f
Original Research
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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.

Design: Double-blind placebo-controlled crossover study with a 6-week washout period.

Setting: Rugby Institute in South Africa.

Participants: College-aged rugby players (n = 20) volunteered for the study, which took place during the competitive season.

Interventions: 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).

Main Outcome Measures: 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.

From the Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa.

Submitted for publication February 1, 2009; accepted July 22, 2009.

Reprints: Kathryn H. Myburgh, PhD, Department of Physiological Sciences, Stellenbosch University, Private Bag XI, Matieland 7602, Stellenbosch, South Africa (e-mail: khm@sun.ac.za).

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