RESUMO
Osteoporosis is less common in obese individuals with increased bone mineral density (BMD) and plasma leptin concentrations. The aim of this study was to determine the correlation between leptin levels and BMD in postmenopausal women. The study consisted of 90 postmenopausal women with a mean age of 53.45 +/- 0.87 years who visited our outpatient clinic for the evaluation of BMD. Thirty-six post-menopausal women with osteoporosis (mean age: 54.52 +/- 1.41 years and mean body mass index (BMI, kg/m2) 29.33 +/- 0.66), 30 age- and BMI-matched postmenopausal women with normal BMD, and 24 postmenopausal women (mean age: 52.79 +/- 1.48 years and mean BMI: 29.45 +/- 0.89) with osteopenic BMD were included in the study. Plasma concentrations of leptin after an overnight fast were measured by radioimmunoassay. BMD values were measured by dual-energy X-ray absorptiometry (DEXA) at the L2-L4 lumbar spine and femoral neck. The median spine BMD value in the patient group (0.67 +/- 0.08 g/cm2, mean +/- SEM) was significantly lower than that in the control group (1.02 +/- 0.25 g/cm2, mean +/- SEM) and osteopenic group (0.87 +/- 0.05 g/cm2, mean +/- SEM) (p < 0.005). The mean spine BMD value (T score -3.63 +/- 0.25, mean +/- SEM) and the mean femur neck BMD value (T score -2.55 +/- 0.18, mean +/- SEM) of the osteoporosis group were significantly lower than that in the normal BMD group (+ 0.33 +/- 0.14 and + 0.27 +/- 0.18, P < 0.001) and in the osteopenia group (-1.74 +/- 0,1 and -1.18 +/- 0.05, p < 0.005). The mean plasma leptin concentration in the osteoporotic group (17.03 +/- 1.40 ng/ml) was not significantly different from that in the normal BMD group and the osteopenia group (16.55 +/- 1.50 ng/ml; 16.16 +/- 1.60, respectively, p > 0.150). Plasma leptin concentrations were correlated with BMI in three groups (r(s) = 0.450, p = 0.025 in normal BMD group and r(s) = 0.4254, P = 0.009 in the osteoporotic group, and r(s) = 395, p = 0.015 in the osteopenia group. There was no correlation between plasma leptin concentrations and BMD values in three groups (r(s) = -0.89 in normal BMD group, r(s) = -0.124 in osteopenia group, and r(s) = -0.195 in osteoporosis group). From this study we conclude that circulating plasma leptin does not have a significant direct influence on bone mass in postmenopausal women.
