Athletes with menstrual disorders have lower estrogen levels, which often leads to lower bone mass. Findings show that a young woman who hasn't menstruated in four years may have the bone density of a 50-year-old woman.
Be sure to increase calcium in your diet (or through supplements), and eat enough calories to keep your body fat or weight from dropping too low. People who are too lean - with a body fat below 12% for the teenaged female athlete -- will not maintain strong bones.