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Exercise plus Amenorrhea Equals Thinner Bones

Adolescent endurance athletes with amenorrhea had significantly lower BMD z scores than did either eumenorrheic athletes or eumenorrheic nonathletes.

Although one benefit of exercise is increased bone-mineral density (BMD), female adult athletes with amenorrhea have low BMD. To examine whether the same is true for female adolescent athletes (age range, 12–18 years), researchers in Boston compared BMD, body composition, and insulin-like growth factor 1 (IGF-1) levels in 21 adolescent athletes with amenorrhea, 18 athletes with normal menstruation, and 18 controls who were not athletes and did not have amenorrhea.

Athletes reported one of the following: at least 4 hours per week of aerobic weight training of the legs, more than 30 miles per week of running, or more than 4 hours per week of endurance training for at least 6 months. Athletes with amenorrhea had missed at least three consecutive cycles following at least 6 months of regular cycles or did not reach menarche by age 15.3 years.

Athletes with amenorrhea had significantly lower BMD z scores (measured by dual-energy radiograph absorptiometry) at the spine and whole body than either eumenorrheic athletes or controls and significantly lower hip BMD z scores than eumenorrheic athletes. Lean mass did not differ among the three groups, but athletes with amenorrhea had lower BMI z scores than eumenorrheic athletes and lower IGF-1 levels than controls. Markers of bone turnover were significantly lower in amenorrheic athletes than in controls. Activity scores were greater for athletes with and without amenorrhea than for controls.

Comment: This study underscores the risk associated with amenorrhea in adolescent athletes and the importance of maintaining regular menses. Unfortunately, the activity questionnaire did not measure energy expenditure so the authors could not determine whether low BMI, increased energy drain, or both lead to amenorrhea. Until this is clarified, athletes must be advised to increase their caloric intake until menses are restored, even if that means an increase in BMI. Although oral contraceptives will restore menses, whether contraceptives enhance bone density is uncertain; therefore, contraceptive use might falsely reassure athletes.

— Alain Joffe, MD, MPH, FAAP

Published in Journal Watch Pediatrics and Adolescent Medicine August 6, 2008

Citation(s):

Christo K et al. Bone metabolism in adolescent athletes with amenorrhea, athletes with eumenorrhea, and control subjects. Pediatrics 2008 Jun; 121:1127.

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