Endocrine Abstracts

The injectable contraceptive depot medroxyprogesterone acetate (DMPA, Depo-Provera^®) is used by over nine million women worldwide. It induces amenorrhoea, raising concern about effects on bone density. This study aims to ascertain if the skeletal effects of DMPA are age-specific and to identity the mechanisms through which DMPA acts on the skeleton. The study was approved by the local Ethics Committee. We recruited 100 pairs of women ages 18–25 and 35–45. DMPA use was of at least 12 months duration and commenced before age 20 or after age 34. Controls were individually matched for source of recruitment, postcode, age, height, BMI and smoking. We previously reported a 5% BMD deficit at the spine and hip in younger DMPA users, and higher bone turnover in DMPA users than controls in both age groups. Combined oral contraceptive users were recruited in the control group, but for each variable COCP users were compared with the rest of the control group and excluded if there was a difference. Measurements were made during the follicular phase in the control group. Oestradiol, SHBG and PTH were higher in the older age group. DHEAS and IGF-1 were lower in the older age group. DMPA users had lower oestradiol than controls (mean (95% CI)); ages 18–25: 25.6 (22.4–29.2) vs 45.9 (31.3–67.4), ages 35–45: 35.1 (30.0–41.3) vs 110.8 (88.6–138.7) pg/ml. DMPA users had higher IGF-1 than controls and younger DMPA users had higher DHEAS than controls. Multiple regression identified oestradiol and IGF-1 as the strongest predictors of bone turnover. Including DMPA in the model reduced the effect of oestradiol, suggesting that the main route through which DMPA acts on bone is oestrogen deficiency.