Chapter 682 Female Athletes

Menstrual Problems and the Risk of Osteopenia

Overtraining in young women can be associated with its effect on reproductive function and bone mineral status especially when combined with calorie restriction (Chapters 26 and 110).

The majority of bone mass is acquired by the end of the 2nd decade (Chapter 698). About 60-70% of adult bone mass is genetically determined, and the remaining is influenced by 3 controllable factors: exercise, calcium intake, and sex steroids, primarily estrogen. Exercise promotes bone mineralization in the majority of young women and is to be encouraged. In girls with eating disorders and those who exercise to the point of excessive weight loss with amenorrhea or oligomenorrhea, exercise can be detrimental to bone mineral acquisition, resulting in reduced bone mineral content, or osteopenia.

Specifically, bone mineralization is negatively affected by amenorrhea (absence of menstruation for ≥3 consecutive months). This may be influenced by abnormal eating patterns, or “disordered eating.” When occurring together, disordered eating, amenorrhea, and osteoporosis form the female athlete triad. At health supervision visits and the preparticipation physical examination, special attention should be given to screening for any features of the triad.

Menstrual abnormalities (including amenorrhea) results from suppression of the spontaneous hypothalamic pulsatile secretion of gonadotropin-releasing hormone. It is believed that the amenorrhea results from reduced energy availability, defined as energy intake minus expenditure. Energy availability below a threshold of 30 kcal/kg/day lean body mass (LBM) is thought to result in menstrual disturbances. Negative energy balance also appears to lower levels of leptin, which affects both nutritional state and the reproductive system. Other causes to be ruled out are pregnancy, pituitary tumors, thyroid abnormalities, polycystic ovary syndrome, anabolic-androgenic steroid use, and other medication side effects.

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