Androstenedione
is a hormone produced by the adrenal glands, ovaries and testes. It's a hormone that's normally converted to testosterone and estradiol in both men and women. Andro is available legally only in prescription form and is a controlled substance.
Manufacturers and bodybuilding magazines tout its ability to allow athletes to train harder and recover more quickly. However, its use as a performance-enhancing drug is illegal in the United States.
Scientific studies that refute these claims show that supplemental androstenedione doesn't increase testosterone and that your muscles don't get stronger with andro use.