A study led by researchers from the Massachusetts General Hospital (MGH) has found that 300 milligram (mg) doses of androstenedione -- a dietary supplement used by some athletes -- can raise blood testosterone levels in healthy young men. The report, in the Feb. 9 issue of the Journal of the American Medical Association also showed an increase in estrogen levels with both 100 and 300 mg doses. It did not examine whether taking androstenedione increases strength or muscle mass or whether androstenedione has long-term side effects.
"A lot of people have been taking androstenedione under the assumption that it will raise their testosterone levels," says Joel Finkelstein, MD, of the MGH Endocrine Unit, the report's senior author. "This is the first study to show that sufficient doses do raise serum testosterone. But we now need to go on and study whether that increase actually translates into changes in athletic performance or into negative health effects."
Androstenedione is a steroid hormone naturally produced in both men and women. Androstenedione produced in the body is converted to either testosterone or to an estrogen. It is widely available as a dietary supplement and primarily marketed to athletes and bodybuilders in the belief that taking it will increase strength, stamina and muscle mass. Currently classified as a dietary supplement under the Dietary Supplement Health and Education Act of 1994, androstenedione is sold over the counter. Its use received wide public attention in 1998 when home run champion Mark McGwire revealed that he had taken the supplement as part of his training regimen.
The MGH-led study was designed only to test the claim that taking oral androstenedione supplements would raise testosterone levels. The research team -- led by Benjamin Leder, MD, also of the MGH Endocrine Unit -- enrolled 42 healthy men aged 20 to 40 with no previous history of taking androstenedione, steroids or any medication known to affect steroid levels. Participants were divided randomly into three groups: 15 received 100 mg daily doses of androstenedione, 14 received 300 mg doses of androstenedione, and 13 received no androstenedione. During the seven-day study, blood tests taken at frequent intervals after participants took the capsules measured levels of four hormones: androstenedione, testosterone and the estrogens estrone and estradiol.
While the 100 mg doses had no significant effect on testosterone levels, the 300 mg doses increased testosterone levels by an average of 34 percent. In one-third of those taking the 300 mg doses, testosterone levels exceeded the normal range for men. Testosterone levels returned to normal within a day of androstenedione administration. Estrogen levels also increased in both the 100 and 300 mg groups: estrone increased 74 percent at 100 mg and 196 percent at 300 mg, and estradiol increased 42 percent at 100 mg and 128 percent at 300 mg.
While this study examined only the direct effect of androstenedione on hormone levels, the authors noted that long-term increases in testosterone or estrogen can have serious side effects in certain susceptible patient populations. Elevated testosterone levels can lower levels of HDL (or "good") cholesterol and can have masculinizing effects on women. Men with increased estrogen levels can experience feminizing effects such as the growth of breasts. Young people who have elevated levels of either hormones could develop early puberty and a premature cessation of bone growth, leading to shorter-than-normal adult height.
The authors also note that the effects of androstenedione were different for different individuals. Some participants developed higher or lower hormone levels, suggesting that certain people may be more or less sensitive to the hormonal effects of androstenedione.
"We simply don't know what the long-term effects are of taking a supplement that changes one's hormone levels," says Leder. "However, if a patient of mine asked whether he should take this supplement, I would have to caution against it."
Additional authors of the JAMA paper are Christopher Longeope, MD, University of Massachusetts Medical School; Don H. Catlin, MD, and Brian Ahrens, University of California at Los Angeles; and David Schoenfeld, PhD, Department of Biostatistics, MGH. The study was supported by equal grants from Major League Baseball and the Major League Baseball Players Association, along with the National Institutes of Health.
Materials provided by Massachusetts General Hospital. Note: Content may be edited for style and length.
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