Douglas S. King, PhD ; Rick L. Sharp, PhD ; Matthew D. Vukovich, PhD ; Gregory A. Brown, MS ; Tracy A. Reifenrath, MS ; Nathaniel L. Uhl ; Kerry A. Parsons, MS
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  pmol/L), 5 (300  pmol/L), and 8 (280  pmol/L) weeks compared with presupplementation values (220  pmol/L).
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.