Androstenedione, commonly known as “andro,” is an anabolic steroid precursor–a non-muscle stimulating steroid hormone that can be converted by the body into another type of steroid that does stimulate muscle growth. Although androstenedione has been credited by a number of famous athletes, like Mark McGwire, for enhancing their athletic abilities, a large amount of research indicates that this is not only untrue, but using the hormone can cause serious side effects.
As the My Fit website explains, androstenedione is a hormone largely produced by the two adrenal glands, located directly above each kidney. According to The Pituitary Foundation, the adrenal glands are stimulated directly into production of their hormones by the pituitary gland. Androstenedione’s main function is to serve as part of the synthesis pathway for the hormones testosterone and estrogen.
Because androstenedione is an essential precursor hormone in the production of testosterone–the main hormone responsible for muscle mass in men–it has been used by a number of athletes interested in increasing their overall muscle growth and enhancing their athletic abilities. By taking supplemental androstenedione, these athletes hope to stimulate the production of larger amounts of circulating testosterone and, with strength training, put on more muscle, faster, than without the androstenedione. Additionally, the U.S. Food and Drug Administration (FDA) reports that androstenedione marketers credit supplements of the hormone with slowing the effects of aging and reducing the overall percentage of body fat.
Despite the claims of many famous athletes, the National Institutes of Health (NIH) reports that research does not support the idea that taking supplemental androstenedione significantly increases muscle mass or athletic ability.
According to the FDA and the NIH, androstenedione use has been linked to acne and stunted growth in users under 18; facial hair growth and an increased risk of blood clots; baldness and breast cancer in women and erectile dysfunction; swelling of breast tissue and testicle shrinkage in men. Androstenedione use has also been directly linked to a decrease in HDL (“good”) cholesterol and an increase in LDL (“bad”) cholesterol, both of which can affect an individual’s likelihood to develop heart disease.
In October 2004, the FDA passed the Anabolic Steroid Control Act, which caused androstenedione, along with a number of other steroids, to be defined as a controlled substance that cannot be used legally without a prescription. The law, which went into effect in January 2005, was met with displeasure by some athletes who believed the government should not interfere with androstenedione use, and approbation by others who felt all sports–such as Mark McGwire’s home run record–were being tainted by drug use.