Oral ethinyl estradiol treatment in women with cystic fibrosis is associated with lower bone mineral density

Objective: The purpose of this study was to determine whether estrogen supplementation primarily from oral contraceptive pills compared to no estrogen supplementation is associated with differences in mean bone mineral density (BMD) measured by DXA in a cross-sectional study of women with cystic fibrosis (CF). Methods: In this cross-sectional study of women with CF followed at a single center, we analyzed 49 women with CF ages 18-50 years with a documented DXA. BMD of women with CF taking estrogen supplementation was compared to BMD of women with CF not taking estrogen supplementation. Results: Twelve women with CF were taking estrogen supplementation with mean dose of 23.3 mcg/day (SD 6.9 mcg/day) of ethinyl estradiol. There were no statistically significant differences between demographics of the 12 women with CF taking estrogen supplementation compared to the 37 women with CF not taking estrogen supplementation. Women taking estrogen had lower mean lumbar spine Z-score: -0.7 +/- 0.7, compared to women not taking estrogen, Z-score: -0.04 +/- 1.0 (p-value 0.046). Women taking estrogen had lower mean BMD at the lumbar spine: 0.952 +/- 0.086 g/cm(2), compared to women not taking estrogen: 1.023 +/- 0.105 g/cm(2) (p-value 0.038). Similar trends were seen at the total hip and femoral neck. Conclusion: Low-dose estrogen supplementation in premenopausal women with CF was associated with lower BMD compared to no estrogen supplementation in a similar group of premenopausal young women with CF. Future studies are needed to investigate the optimal formulation, route of administration, and dose to accrue and preserve bone mass in premenopausal women with CF.