Effects of two low-dose combined oral contraceptives containing drospirenone on bone turnover and bone mineral density in young fertile women: a prospective controlled randomized study.

Background: The effects of a 21-day combined oral contraceptive containing 30 mcg ethinyl estradiol plus 3 mg drospirenone with a 21-day preparation containing 20 mcg ethinyl estradiol plus 3 mg drospirenone on bone turnover and bone mineral density (BMD) in young fertile women were compared.

Methods: A randomized, controlled trial was conducted on healthy fertile women treated with 30 mcg ethinyl estradiol plus 3 mg drospirenone (Group A; n=21), 20 mcg ethinyl estradiol plus 3 mg drospirenone (Group B; n=23) and healthy controls (Group C; n=21). At 3, 6, 9 and 12 months, serum and urinary calcium, osteocalcin (BGP), urinary pyridinoline and deoxypyridinoline were measured. At baseline and after 12 months, lumbar bone mineral density was determined by dual-energy X-ray absorptiometry.

Results: In Groups A and B, urinary pyridinoline and deoxypyridinoline at 6, 9 and 12 months were significantly reduced in comparison with basal values and Group C (p<.05). In Groups A and B, serum calcium levels were significantly increased after 6 months. No significant difference was detected between Groups A and B in urinary levels of pyridinoline and deoxypyridinoline, in calcium levels and in BGP levels. At 12 months, no significant difference was detected in spinal BMD values between the three groups and in comparison with basal values.

Conclusion: Both combined oral contraceptives exert a similar positive influence on bone turnover in young postadolescent women.