Longitudinal evaluation of perimenopausal vertebral bone loss : effects of a low-dose oral contraceptive preparation on bone mineral density and metabolism

The objective of this study was to characterize the pattern of biochemical markers of bone metabolism and vertebral bone mineral density in eumenorrheic and oligomenorrheic perimenopausal women and to assess the effects of a combined oral contraceptive (OC) preparation on bone mass and metabolism. Bone biochemical markers and vertical bone density were evaluated in a longitudinal 2-year follow-up study conducted in healthy normally menstruating perimenopausal women perimenopausal oligomenorrheic women and age-matched oligomenorrheic OC-treated women (20 mcg ethinyl estradiol [E2] plus 0.15 mg desogestrel) (n=27 in each group). The results were analyzed by factorial or repeated-measures analysis of variance as appropriate. During their observation period there were no significant modifications in menstrual cycle plasma FSH and E2 levels biochemical markers of bone turnover and vertebral bone density in normal women. Conversely oligomenorrheic women showed an increase in the cycle length with a concomitant decrease in plasma E2 and a corresponding rise in circulating plasma FSH levels (p < .05). In this group an increase in both urinary excretion of hydroxyproline and plasma osteocalcin levels paralleled a significant decrease in vertebral bone density (p < .0001). In OC-treated women the pattern of osteocalcin showed no modification whereas urinary excretion of hydroxyproline showed a decrease which paralleled a significant (p < .001) increase in vertebral bone density. Perimenopausal OC administration can prevent the increase in bone turnover and the decrease in bone density that follow the perimenopausal impairment of ovarian function. (authors)