Common supplements -Androstenedione. It gained national attention when baseball player Mark McGwire said he used it. It may be converted to testosterone or estrogen in the body. There aren t enough well-conducted large studies to show safety and effectiveness on adults, much less teens. Girls may develop male physical characteristics such as increased facial hair and deeper voice.
Creatine is an amino acid made by the body.
It is stored in the muscles and can help generate bursts of energy. New studies on creatine use in teens are emerging. Long-term studies are needed. Manufacturers say creatine is safe when used properly, which means following recommended dosages and drinking a lot of fluids, especially water. They can stimulate the heart and nervous system.