Effects of gonadal hormone deficiency on bone mineral density : can physical activity increase bone mineral density in women?

Abstract

Osteoporosis with its associated fragility fractures is a global health care problem. The incidence of ftagility ftactures has increased dramatically the last 50 years. This has been suggested to at least in part be due to the sedentary lifestyle in the modem society. The prevalence of osteoporosis increases with increasing age.

In the decade following menopause, most women experience more rapid bone loss than that caused by aging alone. This is mainly due to the decreased ovarian estrogen secretion. Bone mineral density (BMD) decrease can be prevented by estrogen therapy.

One of the aims of these studies was to investigate the effects of decreased levels of gonadal hormones on bone mineral density (BMD) in men and women. Men with prostate cancer were subjected to medical or surgical castration. This led to decreased testosterone levels and decreased bone mineral density. The decrease in bone mass was larger in the surgically castrated group. Treatment of fertile women with GnRH analogues for endometriosis for 6 months and hereby decreased estrogen levels led to a decrease in bone mineral density. Perimenopausal women with fluctuating estradiol levels and occasional ovulations were followed for 18 months. There was a significant decrease in BMD over an 18 months period.

The main aim of this thesis was to study if moderate physical training could prevent the loss of bone mass or even increase BMD in women with low circulating estradiol levels. Therefore young women with endometriosis treated with GnRH analogues for 6 months were randomised to physical training for 12 months or no intervention. The subjects trained during six months of GnRH treatment and during six months following cessation of therapy. Perimenopausal women with fluctuating estradiol levels and postmenopausal women with a forearm fracture and low bone mineral density were randomized to training or to controls for 18 and 12 months respectively.

The results indicate a moderately positive effect of physical training in all three studies. The groups were small and no direct comparison was made. The most pronounced positive effect of training on BMD was found in the young women during six months following cessation of GnRH therapy. The least pronounced effect was found in the postmenopausal women with low stable estradiol levels.

We concluded that moderate physical activity can prevent perimenopausal decrease in BMD, increase BMD in postmenopausal women with low bone mass and increase the speed of recovery of bone mass after GnRH therapy in women of fertile age with endometriosis.