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
To determine if oral administration of androstenedione increases serum
testosterone levels in healthy men.
Open-label randomized controlled trial conducted between October 1998
and April 1999.
General clinical research center of a tertiary-care, university-affiliated
Forty-two healthy men aged 20 to 40 years.
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
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.
Our data suggest that oral androstenedione, when given in dosages of
300 mg/d, increases serum testosterone and estradiol concentrations in some