Three weeks of creatine monohydrate supplementation affects dihydrotestosterone to testosterone ratio in college-aged rugby players.
Level 2 - randomized trial
Double-blind randomized placebo-controlled crossover trial
PubMed 19741313 · doi:10.1097/JSM.0b013e3181b8b52f
What was done
In a double-blind, placebo-controlled crossover study with a 6-week washout period, 20 college-aged male rugby players in South Africa received creatine or a glucose placebo during their competitive season. The creatine regimen consisted of a 7-day loading phase (25 g/day creatine with 25 g/day glucose) followed by a 14-day maintenance phase (5 g/day creatine with 25 g/day glucose), compared against a glucose placebo (50 g/day loading, 30 g/day maintenance). Resting serum total testosterone (T), dihydrotestosterone (DHT), the DHT:T ratio, and body composition were evaluated at baseline, day 7, and day 21.
What was found
Serum testosterone levels showed no significant change after 7 days of loading or after 14 days of maintenance dosing. However, serum DHT levels increased by 56% after 7 days of loading and remained 40% above baseline after the 14-day maintenance period (P < 0.001). The DHT:T ratio increased by 36% after 7 days of loading and remained elevated by 22% above baseline at day 21 (P < 0.01).
Why it matters
This study provides evidence that creatine supplementation can alter circulating androgen metabolism by increasing the conversion of testosterone to DHT, raising mechanistic and safety considerations for athletes using creatine.
Limits
The sample size was small (n = 20) and restricted exclusively to young male rugby players during a competitive season, limiting generalizability to non-athletes, older populations, or females. The study assessed resting serum markers over only 3 weeks and did not measure 5-alpha reductase activity directly, free testosterone, or clinical end-organ androgenic effects (such as hair loss or prostate markers).
Cited by
- supports The claim that creatine causes hair loss originated from a study in rugby players where 20-25 g/day for 7 days increased DHT within the normal biological range without measuring hair loss or thinning.