Longitudinal evaluation of perimenopausal bone loss: effects of different low dose oral contraceptive preparations on bone mineral density.

OBJECTIVES

To evaluate the pattern of mineral density in eumenorrhoic and oligomenorrhoic perimenopausal women, and assess the effects of different low dose oral contraceptives (OC) on bone metabolism and spine bone density.

METHODS

Spine bone density was evaluated in a longitudinal 2-year follow-up, randomized, unblinded, uncontrolled clinical trial conducted in healthy, normally menstruating perimenopausal women, perimenopausal oligomenorrhoic women and in perimenopausal oligomenorrhoic women treated with an oral contraceptive containing 20 microg ethinyl estradiol plus 0.15 mg desogestrel, 0.100 mg levonorgestrel, 0.75 mg of gestodene (n=15 in each group). The results were analyzed by factorial or repeated measures analysis of variance, as appropriate.

RESULTS

During the observation period, in normal menstruating women there were no changes in menstrual cycle, plasma FSH and estradiol levels, and spine bone density. In oligomenorrhoic untreated women an increase in cycle length, with a concomitant decrease in plasma estradiol and an increase in plasma FSH levels were evidenced (p<0.05). In this group a significant decrease in bone density (p<0.05) occurred. In OC-treated women, a significant (p<0.05) increase in bone density was observed, with no differences among different groups.

CONCLUSION

Different progestins used in OC preparations do not modify the bone sparing effect of perimenopausal OC administration avoiding the decrease in bone density.