TNFRSF11B and Parkinson disease: In contrast, levels of OPG [PD vs HC, 130.7 pg/ml (89.4–207) vs. 169.5 pg/ml (113.1–245), P < 0.001] and BMP2 [PD vs. HC, 11.8 pg/ml (8–20.9) vs. 17.9 pg/ml (9.37–31.5), P < 0.001] were decreased in the PD patients compared to those in controls (Table 1, Figures 1A–D).