Anorexia nervosa, osteoporosis and circulating leptin: the missing link.

UNLABELLED

Methods: Leptin levels were measured in 103 consecutive women with anorexia nervosa. Results: Spine BMD and Z-score values were found to be significantly lower in the low tertile compared with the highest tertile. Duration of amenorrhea and leptin level accounted for 27% of the variance in lumbar spine BMD.

INTRODUCTION

The purpose of this study was to assess leptin levels and other biological variables in a population of anorexia nervosa patients.

METHODS

Leptin levels were measured consecutively in 103 women with anorexia nervosa (AN) with a mean age of 24.9 +/- 7.4 years. Osteodensitometry was also performed by dual energy X-ray absorptiometry (DXA).

RESULTS

Spine bone mineral density (BMD) and Z-score values were found to be significantly lower in the low tertile compared with the highest tertile. Duration of amenorrhea and leptin level accounted for 27% of the variance in lumbar spine BMD. The mean leptin level was 3.9 +/- 4.6 ng/mL (normal values, 3.5-11 ng/mL). The distribution of leptin values was not a Gaussian distribution, and a log-transformed was therefore performed. A significant correlation was found between leptin level and spinal BMD (r = 0.3; p = 0.002); significant correlations were observed for both femoral neck and total hip BMDs. When leptin level values were divided into tertiles, spine BMD and Z-score values were found to be significantly lower in the lower tertile (p = 0.04 and p = 0.02) compared with the highest tertile. For femoral neck BMDs, the T-score was slightly lower between low and high tertile, but the difference was not statistically significant (p = 0.07). When multivariate analyses were performed, two independent factors which could possibly account for the variance in spinal BMDs were found. Duration of amenorrhea and leptin level accounted for 27% of the variance (p < 0.0001).

CONCLUSION

The mechanisms underlying bone loss in AN patients remain unclear and complex, involving hypoestrogenia as well as nutritional factors such as insulin-like growth factor and leptin.