Zhou J, et al. - The association between serum retinol-binding protein 4 (RBP4) with bone mineral density (BMD), and other bone metabolic-related parameters was investigated in type 2 diabetic patients older than 50 years, with or without osteopenia or osteoporosis. After adjustments for other factors in osteopenia and osteoporosis group, serum RBP4 was positively correlated with BMD at all sites compared with normal bone mineral density group of type 2 diabetic patients.