Hormone replacement therapy in perimenopausal women with a low dose oral contraceptive preparation: effects on bone mineral density and metabolism.

In a 2-year longitudinal, calcium-controlled study we evaluated bone density and metabolism in perimenopausal women with initial ovarian failure, and the effects of hormone replacement with a low dose oral contraceptive preparation (OC). In perimenopausal oligomenorrhoic women (n = 16) a significant (P < 0.01) increase in cycle length and plasma FSH levels as well as a parallel decrease in plasma estradiol levels (P < 0.01) were evident. In this group, despite the calcium supplementation (500 mg/day), a significant (P < 0.001) increase in the biochemical markers of bone remodelling paralleled a significant (P < 0.001) decrease (-3.4% after 24 months) in bone density. Conversely, in premenopausal oligomenorrhoic women treated with a low dose oral contraceptive (OC) formulation (30 mcg ethinyl estradiol plus 75 mcg gestodene, n = 16), bone markers showed a significant (P < 0.01) decrease, that paralleled a slight but significant (P < 0.01) increase (+1.71%) in bone density. These data suggest that premenopausal administration of OC can prevent the acceleration of bone turnover and reverse the decrease in bone density that follows the premenopausal impairment of ovarian function.