Context: Androstenedione, a steroid hormone and the major precursor to testosterone, is available without prescription and is purported to increase strength and athletic performance. The hormonal effects of androstenedione, however, are unknown.
Objective: To determine if oral administration of androstenedione increases serum testosterone levels in healthy men.
Design: Open-label randomized controlled trial conducted between October 1998 and April 1999.
Setting: General clinical research center of a tertiary-care, university-affiliated hospital.
Participants: Forty-two healthy men aged 20 to 40 years.
Intervention: Subjects were randomized to receive oral androstenedione (either 100 mg/d [n = 15] or 300 mg/d [n = 14]) or no androstenedione (n = 13) for 7 days.
Main outcome measures: Changes in serum testosterone, androstenedione, estrone, and estradiol levels, measured by frequent blood sampling, compared among the 3 treatment groups.
Results: Mean (SE) changes in the area under the curve (AUC) for serum testosterone concentrations were -2% (7%), -4% (4%), and 34% (14%) in the groups receiving 0, 100, and 300 mg/d of androstenedione, respectively. When compared with the control group, the change in testosterone AUC was significant for the 300-mg/d group (P<.001) but not for the 100-mg/d group (P = .48). Baseline testosterone levels, drawn 24 hours after androstenedione administration, did not change. Mean (SE) changes in the AUC for serum estradiol concentrations were 4% (6%), 42% (12%), and 128% (24%) in the groups receiving 0, 100, and 300 mg/d of androstenedione, respectively. When compared with the control group, the change in the estradiol AUC was significant for both the 300-mg/d (P<.001) and 100-mg/d (P = .002) groups. There was marked variability in individual responses for all measured sex steroids.
Conclusions: Our data suggest that oral androstenedione, when given in dosages of 300 mg/d, increases serum testosterone and estradiol concentrations in some healthy men.