The role of leptin in the etiopathogenesis of anorexia nervosa and bulimia.

Leptin is an adipocyte-derived signal factor (167 amino acid protein) encoded by the ob gene in chromosome 7q31 that regulates eating behaviour via central neuroendocrine mechanisms. It has been shown that serum leptin levels correlate with weight and percentage body fat in normal and obese individuals, but the exact correlation between leptin and body weight in anorexic and bulimic patients has not yet been clarified. We investigated leptin levels in the serum of 58 female subjects aged 15-36 years: 10 with bulimia nervosa (BN); 12 with anorexia nervosa (AN); 12 overweight controls (not BN); 12 weight-reduced controls (not AN); and 12 normal weight controls. The aim of the study was to evaluate the possible correlations between leptin levels and the body mass index (BMI) in all five groups. Our results showed that the serum leptin levels of the bulimic patients were similar to those of the healthy controls, with a positive correlation between leptin and BMI. Although bulimic patients have very bad nutritional behaviour, their leptin levels do not appear altered. Serum leptin was significantly (p<0.001) reduced in the anorexic patients because of the dramatic decrease in adipose mass caused by the nutritional defect, as: is further supported by the significantly (p<0.001) low level of transferrinemia. Our data suggest that, although significantly reduced, serum leptin levels in fasting anorexic patients are non-linearly related to body weight (BMI).