Short-term response of bone turnover to low-dose oral contraceptives in exercising women with hypothalamic amenorrhea.

We examined the response of bone turnover markers and indices of energy status after 2 weeks of oral contraceptive (OC) therapy in premenopausal women with exercise-associated menstrual disturbances (EAMD). Six women with EAMD received one 28-day cycle of a triphasic OC containing 180-250 mcg norgestimate/25 mcg ethinyl estradiol (EAMD+OC) and six were controls (EAMD controls). Bone turnover markers amino-terminal propeptide of Type I procollagen and serum carboxy-terminal telopeptides of Type I collagen (PINP and SCTX-I) were assessed at baseline and after 2 weeks of OC therapy (EAMD+OC) or after a 30-day monitoring period (EAMD controls). Total triiodothyronine, resting energy expenditure (REE) and dietary intake were assessed as secondary end points. The absolute and percent changes from baseline in the primary and secondary outcomes were evaluated using an analysis of covariance, adjusting for baseline values of the corresponding outcome. Compared to EAMD controls, a significant change from baseline was observed in the EAMD+OC group for PINP (mean+/-SEM, 9.9+/-6.1 vs. -33.9+/-9.0 mcg/L; p=.005) and SCTX-I (-0.02+/-0.11 vs. -0.25+/-0.07 ng/mL; p=.017), but not osteoprotegerin (-0.53+/-0.22 vs. 0.20+/-0.44 pmol/L; p=.429) after 2 weeks (14.7+/-0.3 days) of OC therapy. Total triiodothyronine levels were elevated in the EAMD+OC group after therapy compared with EAMD controls (19.7+/-4.1 vs. -8.4+/-4.9 ng/dL; p=.002); however, no differences between groups were observed for the changes in REE or dietary intake. Our data demonstrate that 2 weeks of low-dose OC therapy rapidly reduced markers of bone resorption and formation, without any significant impact on energy status in women with EAMD.