Effect of oral androstenedione on serum testosterone and adaptations to resistance training in young men: a randomized controlled trial.

CONTEXT: Androstenedione, a precursor to testosterone, is marketed to increase blood testosterone concentrations as a natural alternative to anabolic steroid use. However, whether androstenedione actually increases blood testosterone levels or produces anabolic androgenic effects is not known. OBJECTIVES: To determine if short- and long-term oral androstenedione supplementation in men increases serum testosterone levels and skeletal muscle fiber size and strength and to examine its effect on blood lipids and markers of liver function. DESIGN AND SETTING: Eight-week randomized controlled trial conducted between February and June 1998. PARTICIPANTS: Thirty healthy, normotestosterogenic men (aged 19-29 years) not taking any nutritional supplements or androgenic-anabolic steroids or engaged in resistance training. INTERVENTIONS: Twenty subjects performed 8 weeks of whole-body resistance training. During weeks 1, 2, 4, 5, 7, and 8, the men were randomized to either androstenedione, 300 mg/d (n = 10), or placebo (n = 10). The effect of a single 100-mg androstenedione dose on serum testosterone and estrogen concentrations was determined in 10 men. MAIN OUTCOME MEASURES: Changes in serum testosterone and estrogen concentrations, muscle strength, muscle fiber cross-sectional area, body composition, blood lipids, and liver transaminase activities based on assessments before and after short- and long-term androstenedione administration. RESULTS: Serum free and total testosterone concentrations were not affected by short- or long-term androstenedione administration. Serum estradiol concentration (mean SEM) was higher (P<.05) in the androstenedione group after 2 (310 20 pmol/L), 5 (300 30 pmol/L), and 8 (280 20 pmol/L) weeks compared with presupplementation values (220 20 pmol/L). The serum estrone concentration was significantly higher (P<.05) after 2 (153 12 pmol/L) and 5 (142 15 pmol/L) weeks of androstenedione supplementation compared with baseline (106 11 pmol/L). Knee extension strength increased significantly (P<.05) and similarly in the placebo (770 55 N vs 1095 52 N) and androstenedione (717 46 N vs 1024 57 N) groups. The increase of the mean cross-sectional area of type 2 muscle fibers was also similar in androstenedione (4703 471 vs 5307 604 mm2; P<.05) and placebo (5271 485 vs 5728 451 mm2; P<.05) groups. The significant (P<.05) increases in lean body mass and decreases in fat mass were also not different in the androstenedione and placebo groups. In the androstenedione group, the serum high-density lipoprotein cholesterol concentration was reduced after 2 weeks (1.09 0.08 mmol/L 42 (3) mg/dL vs 0.96 0.08 mmol/L 37 (3) mg/dL; P<.05) and remained low after 5 and 8 weeks of training and supplementation. CONCLUSIONS: Androstenedione supplementation does not increase serum testosterone concentrations or enhance skeletal muscle adaptations to resistance training in normotestosterogenic young men and may result in adverse health consequences.