Osteoprotegerin is strongly associated with calcium and magnesium in seminal fluid but not affected by denosumab

Objective While the effect of the RANKL-inhibitor denosumab on serum minerals is well-documented, its impact on seminal fluid minerals is poorly understood. This study examines the correlation between the high levels of soluble-RANKL, osteoprotegerin (OPG), and minerals in seminal fluid and whether this can be influenced by denosumab. Methods Two cohorts comprised this study: 100 young men from the general Danish population with no reported fertility issues, and 91 infertile men who were treated with a single dose of denosumab (60 mg), or placebo in a randomized controlled trial assessing the effect on semen quality. Each man underwent a physical examination and semen analysis, including analysis of soluble RANKL, OPG, calcium, magnesium, and phosphate in the seminal fluid. Results In both men from the general population and infertile men, seminal OPG concentrations were positively correlated with seminal calcium (r normal =0.54 and r infertile =0.81), seminal magnesium (r normal =0.58 and r infertile =0.75), and a weak negative correlation was seen with seminal phosphate (r normal =-0.17 and r infertile =-0.34) concentrations. Seminal soluble RANKL was not associated with seminal minerals. Following 60 mg denosumab treatment, no changes were observed after 160 days in seminal calcium ( p = 0.42), magnesium ( p = 0.55), or phosphate concentrations ( p = 0.63). Changes in seminal OPG were moderately negatively correlated with changes in serum AMH ( r =-0.32), LH ( r =-0.30), and FSH ( r =-0.31). Conclusion A strong correlation between OPG and minerals in seminal fluids from both normal and infertile men suggests that the release of these factors by the prostate or seminal vesicle is regulated by the same factors, but cannot be modified by a short-term systemic RANKL inhibition with denosumab. Clinical trial registration ClinicalTrials.gov NCT03030196. Registered January 24, 2017.