Low serum osteoprotegerin levels in premenopausal infertile women with low bone density: an association of relevance?

Objective: To evaluate if the levels of the central regulators of osteoclast activity, osteoprotegerin (OPG) and receptor activator for nuclear factor κB-ligand (RANk-L), correlate with bone mineral density (BMD) parameters in premenopausal infertile women. Design: Cross-sectional study. Setting: Academic infertility practice. Patient(s): 82 Infertile, but otherwise healthy, premenopausal women< 42 years age presenting for routine care. Intervention(s): BMD assessment; serum samples (cycle days 1 to 3), questionnaire addressing demographics, medical, social, family, and personal histories. Main Outcome Measure(s): BMD categorized as "Low" (Z ≤ -1.0) or "Normal" (Z > -1.0); Biomarkers of bone metabolism (BAP, TRAP, NTX, OPG, RANK-L) and ovarian reserve (FSH, estradiol). Result(s): The prevalence of low BMD was 23% (19/82). Significantly lower levels of OPG were observed in association with low BMD compared with normal BMD (1.37 ± 0.57 versus 2.0 ± 1.05 pMol/L). Multivariable logistic regression analyses revealed low OPG levels as independent predictors of low BMD after adjusting for parameters known to influence bone density. Conclusion(s): We demonstrate an independent relationship between low circulating levels of OPG and low BMD in premenopausal healthy, albeit infertile, women.