Trabecular bone density and menstrual function in women runners

Abstract

Osteoporosis results in decreased bone mineral mass and reduced trabecular bone density. Although its etiol ogy remains unknown, studies have revealed differen tial changes in the bone mineral densities of postmeno pausal women, anorexic women, and amenorrheic fe male athletes. Correlations have also been made be tween estrogen deficiency and osteoporosis in both premenopausal and postmenopausal women. In order to examine the possibility of osteopenia, a group of 36 female runners between the ages of 15 and 44 years were evaluated for bone mineral density, menstrual function, and dietary habits. Serum calcium, phospho rus, and parathyroid hormone (PTH) levels were also determined for each participant, as were complete blood counts. Using dual photon absorptiometry, all participants underwent a 20 minute scan of the lumbar spine with specificity to the L1-14 vertebrae. The 36 subjects included 19 oligomenorrheic and 17 eumenor rheic women. Results of bone density analyses re vealed that the oligomenorrheic runners had signifi cantly lower calibrated bone mineral density (CBMD) than their eumenorrheic counterparts ( P << 0.01 ). Like wise, the PTH levels of the oligomenorrheic runners were also significantly lower ( P << 0.01). Analysis of dietary logs revealed no significant differences between the dietary habits, the calcium intake, or the caloric intake of the two groups. The data from this study indicate that there is a relationship between reduced serum PTH levels and the oligomenorrheic state. The loss of the protective effect of estrogen in the oligo menorrheic runners possibly contributed to their re duced bone mineral densities and could be a contrib uting factor in osteopenia.