Androstenedione (andro) is a hormone produced by the adrenal glands, ovaries and testes. It's a precursor hormone that's normally converted to testosterone and estradiol in both men and women.

Manufacturers of synthetic androstenedione, through vigorous marketing efforts, have claimed that their products increase your body's production of testosterone. According to proponents of andro supplements, an elevated level of testosterone allows athletes to train harder and recover more quickly.

Scientific studies that refute these claims are now emerging. In fact, these studies show that supplemental androstenedione doesn't increase testosterone and that your muscles don't get stronger with andro use.

On Oct. 22, 2004, the Anabolic Steroid Control Act of 2004 classified andro as a controlled substance, adding it to the list of banned anabolic steroids and making its use as a performance-enhancing drug illegal.

Side effects of andro differ for men and women. In men it can actually decrease the production of testosterone while increasing the production of estrogen. Side effects in men include acne, diminished sperm production, shrinking of the testicles and enlargement of the breasts. In women, side effects include acne and masculinization, such as deepening of the voice and male-pattern baldness. Andro might also stunt your child's growth.

In men and women, supplemental androstenedione can decrease high-density lipoprotein (HDL) cholesterol (the "good" cholesterol). Lower HDL levels put you at greater risk of heart attack and stroke.