Relationship between physical activity level and bone mineral density in two groups of female athletes

In order to evaluate the possible relationships among hormonal status, physical activity and bone density, we carried out a study on two groups of female athletes engaged in different levels of physical activity. We measured the following hormones: luteinizing hormone (LH), folliculo-stimulating hormone (FSH), 17-beta-oestradiol (E2), progesterone (PRG), prolactin (HPRL), estrone (E1), thyreo-stimulating hormone (TSH), free thyroxine (FT4), and the markers of phosphate-calcium metabolism: calcitonine (CT), parathormone (PTH), and osteocalcine (BGP). We also measured bone mineral density (BMD). All of these variables were related to the amount of work performed during training. The groups were defined as follows: medium workload (group M, n = 10) and heavy workload (group H, n = 20), engaged in 10 and 18 hours of weekly training at 35 and 60 average percent of VO2max, respectively. All of the hormones and the markers of calcium-phosphate metabolism studied were normal; BMD was also normal for all subjects except for two sisters in group M with reduced BMD. The group H athletes with regular menstrual cycles were found to have an upper limit normal BMD. From these data we conclude that in regularly menstruating athletes an increase in BMD induced by heavy physical activity is evident, while in dysmenorrhoeic athletes the effect of physical activity compensates, to some extent, for the hypothetical bone mineral reduction possibly caused by the hormonal imbalance.