Effects of the contraceptive patch and the vaginal ring on bone metabolism and bone mineral density: a prospective, controlled, randomized study

Abstract

Background: This study was conducted to compare the effects of the combined contraceptive vaginal ring releasing 15 mcg of ethinylestradiol (EE) and 120 mcg of etonorgestrel daily with the effects of the contraceptive patch, a transdermal system that delivers a daily dose of 20 mcg of EE and 150 mcg of norelgestromin on bone turnover and bone mineral density (BMD) in young fertile women.

Study design: On the basis of a randomized, computer-generated list, 40 women desiring contraception were assigned to a 12-month treatment with a patch delivering a daily dose of 20 mcg of EE and 150 mcg of norelgestromin (Evra, Janssen-Cilag, Italy) (Group A, n=20) or to a 12-month treatment with a vaginal ring releasing a daily dose of 15 mcg of EE and 120 mcg of etonorgestrel (NuvaRing, Organon, Italy) (Group B, n=20). Twenty patients underwent no treatment and were used as healthy controls (Group C, n=20). At 3, 6, 9 and 12 months, serum and urinary calcium, osteocalcin and urinary pyridinoline (PYD) and deoxypyridinoline (D-PYD) levels were measured. At baseline and after 12 months, lumbar BMD was determined by dual-energy X-ray absorptiometry.

Results: In Groups A and B, urinary PYD and D-PYD at 6, 9 and 12 months were significantly reduced in comparison with basal values and Group C values (p<.05). In Groups A and B, serum calcium levels were significantly increased after 6 months. No significant difference was detected between Group A and Group B in urinary levels of PYD and D-PYD, in calcium levels and in osteocalcin 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 contraceptive systems exert a similar positive influence on bone turnover in young postadolescent women.