Differential effects on bone density of progestogen-only methods for contraception in premenopausal women

The question of differential effects on bone density by two different types of progestogen-only methods for contraception in premenopausal women was addressed. Data from a prospective randomized clinical trial among 22 premenopausal women, age 32.6 (range 20-45 years), who were randomly assigned to either of two treatments with continuous progestogens for contraception were analyzed; depot-medroxyprogesterone acetate (DMPA) or continuous levonorgestrel treatment with subdermal implants (Norplant), respectively. Forearm bone density (BMDprox) increased with 2.94% (p = 0.006) in women who were prescribed levonorgestrel, which was in contrast to stable values in those prescribed depot-medroxy-progesterone acetate; group difference at 6 months for BMDprox 3.4% (95% CI 1.3, 5.5; p = 0.025) and BMDdist 4.1% (95% CI - 1.3, 9.6; p = 0.077). The changes in bone density were consistent with the changes in biochemical indices for bone metabolism; DMPA users showed signs of increased bone turnover and users of levonorgestrel showed increased bone formation with increased levels of both alkaline phosphatase (p = 0.004) and osteocalcin (p = 0.007). The findings suggest an increase in bone density during treatment with levonorgestrel and stable values during short-term administration of DMPA, in standard clinical doses for contraception.