Relationship between serum leptin levels and bone mineral density and bone metabolic markers in patients on hemodialysis

Leptin is the protein product of the obesity gene, which is produced in fat tissue. It was originally thought to be involved only in the regulation of food intake and energy balance. We aimed to investigate the relationship of serum leptin levels with bone mineral density (BMD) and biochemical markers of bone turnover in patients on hemodialysis (HD). This study included 72 patients (43 males and 29 females), whose mean age was 55.1 ± 11.4 years, mean body mass index was 23.13 ± 2.75 kg/m 2 and mean duration on HD was 5 ± 3.4 years. The BMD values were calculated using dual-energy X-ray absorptiometry (DEXA) at the femoral neck and lumbar spine. Blood samples were taken for leptin, intact parathyroid hormone (I-PTH), bone alkaline phosphatase (BAP), calcium (Ca), phosphate (P) and albumin. The leptin levels were higher in females than in males (22.3 ± 19.6 vs 20.8 ± 23), but this difference was not significant. The serum leptin level had a strong positive correlation with Ca levels in the female patients (r = 0.659 and P = 0.01) and a negative correlation with albumin levels (r = -0.461 and P = 0.01). No correlation was found with age, BMI, duration on dialysis, BMD and serum levels of PTH, BAP and P for the entire patient group or either gender separately. The serum leptin level was significantly lower in females with PTH >300 pg/mL when compared with patients with PTH = 100-300 pg/mL (86 ± 85 vs 47 ± 48) (P = 0.011).Women with BAP