Fig. 2.

Relationship between the leptin/BMI (body mass index) ratio and bone metabolic markers including serum bone-specific alkaline phosphatase (BAP), carboxyterminal propeptide of type I procollagen (PICP), and urine deoxypyridinoline (DPD), serum insulin and fructosamine (FRA) concentrations, and the number of vertebrae with OPLL (ossification of the posterior longitudinal ligament) involvement in female OPLL patients. There was a negative, significant correlation between the leptin/BMI ratio and urine DPD levels, while a positive, significant correlation between the leptin/BMI ratio and serum insulin levels, and the number of vertebrae with OPLL involvement