Role of leptin in legg–calvé–perthes disease

Obesity is considered a clinical risk sign for Legg–Calvé–Perthes disease (LCPD). Leptin is primarily secreted by adipocytes, and it regulates adipose tissue mass and body weight. Furthermore, obesity is clearly associated with increased leptin levels. We investigated the roles of leptin and the soluble leptin receptor (sOB‐R) in LCPD. This matched case–control study included 38 male and 3 female patients with LCPD, and an equal number of age—(range was 4–12) and sex‐matched control patients with healthy fractures. Serum leptin and sOB‐R levels were quantified with ELISA. The free leptin index (FLI) was defined as the ratio of leptin to sOB‐R levels. Serum leptin levels, sOB‐R, and FLI were compared between groups. The relationship between leptin, disease severity, and treatment outcomes were analyzed in the LCPD group. There were no significant differences between groups in terms of age, sex, and body mass index (BMI) percentile. Mean leptin levels (p = 0.042), sOB‐R levels (p = 0.003), and FLI (p = 0.013) differed significantly between groups. In the LCPD group, the serum leptin levels, sOB‐R levels, and FLI differed significantly between the lateral pillar and Stulberg classification groups (p < 0.05). Also, the leptin levels and FLI increased significantly according to the lateral pillar and Stulberg classifications even after adjusting for age and BMI percentile (p < 0.05). Circulating leptin and FLI were significantly higher in the LCPD group. Furthermore, leptin, disease severity, and treatment outcomes were associated. This correlation suggests that leptin might play an important role in LCPD pathogenesis. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1605‐1610, 2013