Although this study supported an inverse correlation between circulatory levels of OPG with BMD measurement, which highlights the potential link between nephrolithiasis and reduced bone mass, but due to the cross-sectional nature of our study cautious the causal assumption between them; whether reduced bone mass brings high levels of OPG in nephrolithiasis or that high levels of OPG in nephrolithiasis brings low bone mass. The gene discussed is TNFRSF11B; the disease is nephrolithiasis.