INTRODUCTION: Conflicting data exist regarding the role of leptin in bone metabolism. The purpose of the present study was to investigate serum leptin concentrations in male patients with haemophilia A and B, a disease known to be associated with low bone mass.MATERIAL AND METHODS: Eighty-one male patients, aged 45.4 ±15 years, were screened. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) in lumbar spine (LS), femoral neck (FN) and total hip (TH).RESULTS: Low bone mass was diagnosed in 20 patients (24.7%). Serum leptin concentrations were strongly associated with body weight (r s = 0.457, p = 0.0001) and body mass index (BMI) (r s = 0.491, p = 0.0001). In unadjusted analysis leptin was inversely associated with BMD in LS (r s = -0.255, p = 0.023), but not in FN and TH (r s = -0.205, p = 0.068 and r s = -0.191, p = 0.090, respectively). However, after adjusting for BMI and body weight, leptin was inversely associated with BMD in FN (F 1,76 = 7.727, p = 0.007, β = -0.371, ΔR (2) = 0.089) and TH (F 1,76 = 4.533, p = 0.036, β = -0.290, ΔR (2) = 0.054), but not in LS (F 1,75 = 2.076, p = 0.154, β = -0.202, ΔR (2) = 0.026). No association was found between age, presence of HBV, HCV or HIV infection or alkaline phosphatase and leptin levels.CONCLUSIONS: Our study showed a negative association between circulating leptin levels and bone mass in males, independently of body weight and BMI.