Bone mineral content and levels of gonadotropins and estrogens in amenorrheic running women.

Serum gonadotropin and estrogen levels and their relationship to bone mineral content in exercise-related amenorrhea were studied in 11 amenorrheic women and 24 eumenorrheic women, all of whom were runners. Serum estradiol, LH, FSH, estrone, and testosterone were measured in serial blood samples obtained at 15-min intervals for 4 h. The amenorrheic women had lower estradiol, LH, FSH; and estrone levels as well as a higher estrone-estradiol ratio than did the eumenorrheic women. There was no difference in testosterone levels. The amenorrheic women had lower LH pulse amplitudes, whereas no differences were found in FSH pulse amplitudes. LH and FSH pulse frequencies did not differ between the two groups. Bone mineral content of the lumbar spine was lower in amenorrheic women and was positively correlated with estradiol levels in all women. There was no difference in bone mineral content of the radius. These data suggest that, in exercise-related amenorrhea, low serum LH, FSH, and estrogen levels reflect an alteration in the hypothalamic control of gonadotropin release. Reduced circulating estrogen levels in amenorrheic running women may be a cause of low mineral content of the spine.