Huang N, et al. - Experts scrutinized the connection between serum retinol binding protein 4 (RBP4), bone mineral density (BMD) and other bone metabolic-related parameters in patients with type 2 diabetes older than 50 years, with or without osteopenia or osteoporosis. From December 2015 to March 2017, patients with type 2 diabetes, hospitalized in the Endocrinology Department of Yantai Yuhuangding Hospital were recruited. Compared with normal bone mineral density group of type 2 diabetic patients, serum RBP4 was positively associated with BMD at all sites after adjustments for other factors in osteopenia and osteoporosis groups.