Effects of contraceptive use on bone biochemical markers in young women

The purpose of this study was to compare biochemical markers of bone resorp tion and formation in young women using different hormonal contraceptive me thods. Women aged 18-39 yr who were using depot medroxyprogesterone acetate (DMPA) contraception were recruited for the study; comparison women were m atched by age and clinic location. There were 116 women using DMPA, 39 usin g oral contraceptives containing estrogen and progestin, and 72 not current ly using hormonal contraceptives. Biochemical measurements were serum calci um, PTH and osteocalcin, and urine N-telopeptide. Bone density was measured using dual-energy x-ray absorptiometry. The N-telopeptide levels, adjusted for age and other risk factors, were 42.4 +/- 2.3 nmol/mmol creatinine in the DMPA group, 26.2 +/- 3.3 nmol/mmol in the oral contraceptive group, and 35.4 +/- 2.9 nmol/mmol in the nonusers; significant differences were seen in all pairwise comparisons. Osteocalcin levels showed the same pattern, al though the difference between the DMPA users and nonusers was not statistic ally significant. There were no differences among groups in the PTH levels. The bone density at the spine was 1.086 +/- 0.085 g/cm(2) in the DMPA grou p, 1.103 +/- 0.095 g/cm(2) in the oral contraceptive group, and 1.093 +/- 0 .090 g/cm(2) in nonusers (P = 0.051). The results suggest that in women usi ng DMPA bone resorption exceeded bone formation.