This study was designed to determine whether the hypoestrogenic status of 14 amenorrheic athletes was associated with a decrease in regional bone mass relative to that of 14 of their eumenorrheic peers. The two groups of athletes were matched for age, height, weight, sport, and training regimens. Bone mass was measured by dual-photon and single-photon absorptiometry at the lumbar vertebrae (L1 to L4) and at two sites on the radius. Vertebral mineral density was significantly lower in the amenorrheic group (mean, 1.12 g per square centimeter) than in the eumenorrheic group (mean, 1.30 g per square centimeter). There was no significant difference at either radial site. Radioimmunoassay confirmed a lower mean estradiol concentration (amenorrheic group, 38.58 pg per milliliter; eumenorrheic group, 106.99 pg per milliliter) and progesterone peak (amenorrheic group, 1.25 ng per milliliter; eumenorrheic group, 12.75 ng per milliliter) in the amenorrheic women, in four venous samples drawn at seven-day intervals. A three-day dietary history showed no significant differences in nutritional intake, including calcium with and without supplements. The two groups were similar in percentage of body fat, age at menarche, years of athletic participation, and frequency and duration of training but differed in number of miles run per week (amenorrheic group, 41.8 miles [67.3 km]; eumenorrheic group, 24.9 miles [40.1 km]). We conclude that the amenorrhea that is observed in female athletes may be accompanied by a decrease in mineral density of the lumbar vertebrae.

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Amenorrheic athletes have been found to have a lower vertebral bone mineral density (BMD) than matched groups of eumenorrheic athletes. This study reports changes in BMD over a 15.5 month period in athletes who regained menses, athletes who remained amenorrheic, and athletes with regular cycles. The BMD was measured at two sites on the radius and at the lumbar vertebrae (L-1 through L-4), using single- and dual-photon densitometry, respectively. Changes in vertebral BMD were significant for the amenorrheic group (+6.3%), but not for cyclic women (-0.3%). A slight increase in radial density at S-1 and S-2 was not significant for either group. Two athletes who remained amenorrheic during this period continued to lose bone (-3.4%). We conclude that resumption of menses was the primary factor for the significant increase in the vertebral BMD of the formerly amenorrheic athletes.

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