The effects of oral contraceptive use on bone mineral density in pre- and post-menopausal women were evaluated in two separate studies. First, in a population of young women carefully controlled for all risk factors known to be associated with osteoporosis, it was determined that vertebral bone mineral was increased by about 1% for each year of exposure to oral contraceptives. A similar result was obtained by examining vertebral mineral content of an unselected, but healthy premenopausal population. Effects of oral contraceptives on bone mass could not be found among postmenopausal women, unless perhaps in the initial year or two after loss of ovarian function.
PIP: The effects of oral contraceptive use on bone mineral density in pre- and post-menopausal women were evaluated in 2 separate studies. 1st, in a population of young women carfully controlled for all risk factors known to be associated with osteoporosis, it was determined that vertebral bone mineral was increased by about 1% for each year of exposure to oral contraceptives. On a rough calculation, 5-10 years of use of oral contraceptives could significantly reduce th incidence of osteoporosis if the trend were maintained and result in a 5-10% increase in bone mass in that population and if thses differences could be maintained after menopause. A similar result was obtained in a 2nd study by examining vertebral mineral content of an unselected, but healthy premenopausal population. However, the effect was not observed in the post-menopausal women, with perhaps the exception of the initial 2 years of post-menopausal period. This suggests that the onset of estrogen deficiency with ovarian failure is a sufficiently potent stimulus to the skeleton that the resulting loss of bone would be sufficient to negate the pre-menopausal oral contraceptive effect. Prospective data would be needed to substantiate this finding. Clearly, if oral contraceptive exposure can be expected to have a long-term effect on bone, prevention of post-menopausal bone loss will still be required after cessation of oral contraceptive treatment.