Introduction: Leptin is considered to exert dual effect on bone metabolism: anabolic (through peripheral pathways) and antiosteogenic (through central nervous system). The total leptin’s effect on bone is not known. The aim of the study was to examine bone metabolism and leptin concentration in patients with morbid obesity before and after bariatric surgery (BS).
Material and methods: Forty one patients with morbid obesity selected for BS were included in the prospective study. Body mass index (BMI), serum leptin, parathyroid hormone (PTH), 25-hydroxyvitaminD (25(OH)D) concentrations and bone mineral density (BMD) in the lumbar spine (LS) and proximal femur (PF) were examined before and 6 months after BS.
Results: Before operation (mean BMI 44.0 kg/m²) mean leptin and PTH concentration was increased (accordingly 37.1 ng/ml and 82.7 pg/ml), mean 25OHD concentration was decreased to 4.3 ng/ml. Mean BMD was within the upper limit of the population reference range. Leptin concentration was positively correlated with BMI. There was no correlation of leptin with BMD (in LS and PF), PTH and 25(OH)D. Following the operation (mean BMI 31.8 kg/m²) mean leptin concentration decreased by 30.6 ng/ml (p < 0.001), PTH decreased by 38.9 pg/ml (p < 0.001), 25(OH)D increased by 2.1 ng/ml (NS). Mean BMD in LS increased by 0.067 g/cm² (p < 0.005), in PF decreased by 0.044 g/cm² (p < 0.02). Leptin was positively correlated with BMI but not with BMD (in both sites), PTH, 25(OH)D.
Conclusions: Weight loss in patients with morbid obesity after BS leads to decrease in serum leptin, increase in BMD in LS and decrease in PF. These changes are accompanied by regression of hyperparathyroidism, which is probably secondary to vitamin D deficiency.