Young ballerinas headed for a dance career may be headed for trouble instead -- if they are pushed too much, too early. According to the American Academy of Pediatrics and the American Academy of Orthopaedic Surgeons, adolescent female dancers can suffer a host of harmful physiologic changes.

One type of abnormality is hormonal: the absence of menstrual periods (amenorrhea), decreased circulating estrogen, and other metabolic changes. It is not exactly clear why these problems occur. They may be due to low levels of body fat, or the poor nutritional status that leads to low body fat. Several studies have shown dietary intakes of young athletes and dancers to be inadequate in calories, nutritional components, vitamins, and minerals.

The psychological stress of competitive dance may also be a factor in the absence of menstrual periods. And the increased emphasis by the young ballet dancers -- and their instructors, judges, and audience -- on having a slender physique can compound the pressure. A high intensity of exercise combined with poor nutritional status can become entwined in a cycle of fasting and purging (vomiting, laxative use) and the emergence of true eating disorders (anorexia and bulimia).

Excessive exercise, amenorrhea, and eating disorders have been termed "the female triad." It is particularly common in young ballet dancers, gymnasts, and long-distance runners, all sports in which a lean body shape is thought to be an asset. According to Joan McGowan, PhD, chief of the musculoskeletal diseases branch of the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Medicine: "This is a very serious health threat. These athletes can develop osteoporosis (thinning of bone, which usually happens only in postmenopausal women), and can actually start to lose bone mass, only stopping when they suffer a stress fracture or a full fracture of the bone."

Teachers and parents need to be aware of the "female triad" and to make an effort to provide young dancers and athletes with adequate calories and nutrients to maintain normal growth and development, and to help these youngsters keep a balanced outlook.