SAN FRANCISCO—Adolescent girls are participating in sports more often than ever before, but some of them may be putting future bone health at risk. Madhusmita Misra, MD, from Massachusetts General Hospital in Boston reported at the ENDO 2008 meeting¹ that up to 24% of adolescent athletes develop amenorrhea, depending on the nature and duration of exercise as well as the athletes’ nutritional status. What’s more, gymnasts, track runners, ballet dancers, and swimmers are at particular risk.

“These girls suffer from menstrual dysfunction at a time when adolescents are supposed to be accruing bone. Peak bone mass in adolescence is an important determinant of later fracture. Menses is an indicator of estrogen status, which is a predictor of bone health, and our concern is that subsequent bone health could be impaired in adolescent athletes who have lost menses,” Dr. Misra told a press briefing.

Not all adolescent athletes develop amenorrhea, and Dr. Misra's group set out to examine neuroendocrine factors that might play a role. “My coinvestigators and I have demonstrated that in adolescent athletes, high levels of ghrelin, which stimulates appetite and low levels of leptin, which decreases appetite, may be important neuroendocrine and metabolic signals that link a decreased energy availability state to menstrual dysfunction,” Dr. Misra reported

Athletes lose menses when energy intake from food cannot keep pace with energy expenditure from exercise. “In decreased energy availability, as in athletes, one would expect that levels of leptin would decrease and levels of ghrelin would increase to try and stimulate food intake as an adaptive mechanism. Also, leptin stimulates and ghrelin inhibits the hormones that regulate estrogen secretion.”

The researchers hypothesized that teenage athletes who had stopped having menses would have lower levels of leptin and higher levels of ghrelin than athletes who continued to have menses. They also expected that these hormonal changes would predict levels of follicle stimulating hormone (FSH) that regulate the secretion of estrogen.

Dr. Misra examined levels of leptin, ghrelin, and sex hormones in 21 teenaged athletes who had stopped menstruating, 19 adolescent athletes who had normal menses, and 18 nonathletic girls ages 12 to 18. Both groups of athletes reported similar levels of athletic activity.

Girls who had stopped menses weighed a little less, were more likely to have disordered eating behavior, and had lower fat mass than athletes who had not stopped menstruating. Levels of ghrelin were higher and levels of leptin were lower in the athletes who had stopped having menses, compared with athletes who had not stopped menstruating and with nonathlete controls.

“Levels of ghrelin were predicted by fat mass and weight, as were leptin levels but, even after controlling for fat mass and weight, we found that levels of ghrelin were higher in the nonmenstruating group. The girls who had the highest levels of ghrelin and the lowest levels of leptin also had the lowest levels of estrogen and FSH. Our data suggest that high ghrelin and low leptin levels may be an important link between being in a state of low energy availability and menstrual dysfunction in the female athlete,” Dr. Misra said.

Reference

1. Misra M. Reproductive bone health in the female athlete. Presented at: ENDO 2008; June 15, 2008; San Francisco, Calif. Presentation S8-2.